// Copyright 2017 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package tsdb

import (
	"bufio"
	"context"
	"encoding/binary"
	"flag"
	"fmt"
	"hash/crc32"
	"math"
	"math/rand"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strconv"
	"sync"
	"testing"
	"time"

	"github.com/go-kit/log"
	"github.com/oklog/ulid"
	"github.com/prometheus/client_golang/prometheus"
	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
	"github.com/stretchr/testify/require"
	"go.uber.org/atomic"
	"go.uber.org/goleak"

	"github.com/prometheus/prometheus/config"
	"github.com/prometheus/prometheus/model/histogram"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/model/metadata"
	"github.com/prometheus/prometheus/storage"
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/tsdb/chunks"
	"github.com/prometheus/prometheus/tsdb/fileutil"
	"github.com/prometheus/prometheus/tsdb/index"
	"github.com/prometheus/prometheus/tsdb/record"
	"github.com/prometheus/prometheus/tsdb/tombstones"
	"github.com/prometheus/prometheus/tsdb/tsdbutil"
	"github.com/prometheus/prometheus/tsdb/wlog"
	"github.com/prometheus/prometheus/util/annotations"
	"github.com/prometheus/prometheus/util/testutil"
)

func TestMain(m *testing.M) {
	var isolationEnabled bool
	flag.BoolVar(&isolationEnabled, "test.tsdb-isolation", true, "enable isolation")
	flag.Parse()
	defaultIsolationDisabled = !isolationEnabled

	goleak.VerifyTestMain(m, goleak.IgnoreTopFunction("github.com/prometheus/prometheus/tsdb.(*SegmentWAL).cut.func1"), goleak.IgnoreTopFunction("github.com/prometheus/prometheus/tsdb.(*SegmentWAL).cut.func2"))
}

func openTestDB(t testing.TB, opts *Options, rngs []int64) (db *DB) {
	tmpdir := t.TempDir()
	var err error

	if opts == nil {
		opts = DefaultOptions()
	}
	opts.EnableNativeHistograms = true

	if len(rngs) == 0 {
		db, err = Open(tmpdir, nil, nil, opts, nil)
	} else {
		opts, rngs = validateOpts(opts, rngs)
		db, err = open(tmpdir, nil, nil, opts, rngs, nil)
	}
	require.NoError(t, err)

	// Do not Close() the test database by default as it will deadlock on test failures.
	return db
}

// query runs a matcher query against the querier and fully expands its data.
func query(t testing.TB, q storage.Querier, matchers ...*labels.Matcher) map[string][]chunks.Sample {
	ss := q.Select(context.Background(), false, nil, matchers...)
	defer func() {
		require.NoError(t, q.Close())
	}()

	var it chunkenc.Iterator
	result := map[string][]chunks.Sample{}
	for ss.Next() {
		series := ss.At()

		samples := []chunks.Sample{}
		it = series.Iterator(it)
		for typ := it.Next(); typ != chunkenc.ValNone; typ = it.Next() {
			switch typ {
			case chunkenc.ValFloat:
				ts, v := it.At()
				samples = append(samples, sample{t: ts, f: v})
			case chunkenc.ValHistogram:
				ts, h := it.AtHistogram(nil)
				samples = append(samples, sample{t: ts, h: h})
			case chunkenc.ValFloatHistogram:
				ts, fh := it.AtFloatHistogram(nil)
				samples = append(samples, sample{t: ts, fh: fh})
			default:
				t.Fatalf("unknown sample type in query %s", typ.String())
			}
		}
		require.NoError(t, it.Err())

		if len(samples) == 0 {
			continue
		}

		name := series.Labels().String()
		result[name] = samples
	}
	require.NoError(t, ss.Err())
	require.Empty(t, ss.Warnings())

	return result
}

// queryAndExpandChunks runs a matcher query against the querier and fully expands its data into samples.
func queryAndExpandChunks(t testing.TB, q storage.ChunkQuerier, matchers ...*labels.Matcher) map[string][][]chunks.Sample {
	s := queryChunks(t, q, matchers...)

	res := make(map[string][][]chunks.Sample)
	for k, v := range s {
		var samples [][]chunks.Sample
		for _, chk := range v {
			sam, err := storage.ExpandSamples(chk.Chunk.Iterator(nil), nil)
			require.NoError(t, err)
			samples = append(samples, sam)
		}
		res[k] = samples
	}

	return res
}

// queryChunks runs a matcher query against the querier and expands its data.
func queryChunks(t testing.TB, q storage.ChunkQuerier, matchers ...*labels.Matcher) map[string][]chunks.Meta {
	ss := q.Select(context.Background(), false, nil, matchers...)
	defer func() {
		require.NoError(t, q.Close())
	}()

	var it chunks.Iterator
	result := map[string][]chunks.Meta{}
	for ss.Next() {
		series := ss.At()

		chks := []chunks.Meta{}
		it = series.Iterator(it)
		for it.Next() {
			chks = append(chks, it.At())
		}
		require.NoError(t, it.Err())

		if len(chks) == 0 {
			continue
		}

		name := series.Labels().String()
		result[name] = chks
	}
	require.NoError(t, ss.Err())
	require.Empty(t, ss.Warnings())
	return result
}

// Ensure that blocks are held in memory in their time order
// and not in ULID order as they are read from the directory.
func TestDB_reloadOrder(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	metas := []BlockMeta{
		{MinTime: 90, MaxTime: 100},
		{MinTime: 70, MaxTime: 80},
		{MinTime: 100, MaxTime: 110},
	}
	for _, m := range metas {
		createBlock(t, db.Dir(), genSeries(1, 1, m.MinTime, m.MaxTime))
	}

	require.NoError(t, db.reloadBlocks())
	blocks := db.Blocks()
	require.Len(t, blocks, 3)
	require.Equal(t, metas[1].MinTime, blocks[0].Meta().MinTime)
	require.Equal(t, metas[1].MaxTime, blocks[0].Meta().MaxTime)
	require.Equal(t, metas[0].MinTime, blocks[1].Meta().MinTime)
	require.Equal(t, metas[0].MaxTime, blocks[1].Meta().MaxTime)
	require.Equal(t, metas[2].MinTime, blocks[2].Meta().MinTime)
	require.Equal(t, metas[2].MaxTime, blocks[2].Meta().MaxTime)
}

func TestDataAvailableOnlyAfterCommit(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)

	_, err := app.Append(0, labels.FromStrings("foo", "bar"), 0, 0)
	require.NoError(t, err)

	querier, err := db.Querier(0, 1)
	require.NoError(t, err)
	seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	require.Equal(t, map[string][]chunks.Sample{}, seriesSet)

	err = app.Commit()
	require.NoError(t, err)

	querier, err = db.Querier(0, 1)
	require.NoError(t, err)
	defer querier.Close()

	seriesSet = query(t, querier, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))

	require.Equal(t, map[string][]chunks.Sample{`{foo="bar"}`: {sample{t: 0, f: 0}}}, seriesSet)
}

// TestNoPanicAfterWALCorruption ensures that querying the db after a WAL corruption doesn't cause a panic.
// https://github.com/prometheus/prometheus/issues/7548
func TestNoPanicAfterWALCorruption(t *testing.T) {
	db := openTestDB(t, &Options{WALSegmentSize: 32 * 1024}, nil)

	// Append until the first mmaped head chunk.
	// This is to ensure that all samples can be read from the mmaped chunks when the WAL is corrupted.
	var expSamples []chunks.Sample
	var maxt int64
	ctx := context.Background()
	{
		// Appending 121 samples because on the 121st a new chunk will be created.
		for i := 0; i < 121; i++ {
			app := db.Appender(ctx)
			_, err := app.Append(0, labels.FromStrings("foo", "bar"), maxt, 0)
			expSamples = append(expSamples, sample{t: maxt, f: 0})
			require.NoError(t, err)
			require.NoError(t, app.Commit())
			maxt++
		}
		require.NoError(t, db.Close())
	}

	// Corrupt the WAL after the first sample of the series so that it has at least one sample and
	// it is not garbage collected.
	// The repair deletes all WAL records after the corrupted record and these are read from the mmaped chunk.
	{
		walFiles, err := os.ReadDir(path.Join(db.Dir(), "wal"))
		require.NoError(t, err)
		f, err := os.OpenFile(path.Join(db.Dir(), "wal", walFiles[0].Name()), os.O_RDWR, 0o666)
		require.NoError(t, err)
		r := wlog.NewReader(bufio.NewReader(f))
		require.True(t, r.Next(), "reading the series record")
		require.True(t, r.Next(), "reading the first sample record")
		// Write an invalid record header to corrupt everything after the first wal sample.
		_, err = f.WriteAt([]byte{99}, r.Offset())
		require.NoError(t, err)
		f.Close()
	}

	// Query the data.
	{
		db, err := Open(db.Dir(), nil, nil, nil, nil)
		require.NoError(t, err)
		defer func() {
			require.NoError(t, db.Close())
		}()
		require.Equal(t, 1.0, prom_testutil.ToFloat64(db.head.metrics.walCorruptionsTotal), "WAL corruption count mismatch")

		querier, err := db.Querier(0, maxt)
		require.NoError(t, err)
		seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchEqual, "", ""))
		// The last sample should be missing as it was after the WAL segment corruption.
		require.Equal(t, map[string][]chunks.Sample{`{foo="bar"}`: expSamples[0 : len(expSamples)-1]}, seriesSet)
	}
}

func TestDataNotAvailableAfterRollback(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	app := db.Appender(context.Background())
	_, err := app.Append(0, labels.FromStrings("foo", "bar"), 0, 0)
	require.NoError(t, err)

	err = app.Rollback()
	require.NoError(t, err)

	querier, err := db.Querier(0, 1)
	require.NoError(t, err)
	defer querier.Close()

	seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))

	require.Equal(t, map[string][]chunks.Sample{}, seriesSet)
}

func TestDBAppenderAddRef(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app1 := db.Appender(ctx)

	ref1, err := app1.Append(0, labels.FromStrings("a", "b"), 123, 0)
	require.NoError(t, err)

	// Reference should already work before commit.
	ref2, err := app1.Append(ref1, labels.EmptyLabels(), 124, 1)
	require.NoError(t, err)
	require.Equal(t, ref1, ref2)

	err = app1.Commit()
	require.NoError(t, err)

	app2 := db.Appender(ctx)

	// first ref should already work in next transaction.
	ref3, err := app2.Append(ref1, labels.EmptyLabels(), 125, 0)
	require.NoError(t, err)
	require.Equal(t, ref1, ref3)

	ref4, err := app2.Append(ref1, labels.FromStrings("a", "b"), 133, 1)
	require.NoError(t, err)
	require.Equal(t, ref1, ref4)

	// Reference must be valid to add another sample.
	ref5, err := app2.Append(ref2, labels.EmptyLabels(), 143, 2)
	require.NoError(t, err)
	require.Equal(t, ref1, ref5)

	// Missing labels & invalid refs should fail.
	_, err = app2.Append(9999999, labels.EmptyLabels(), 1, 1)
	require.ErrorIs(t, err, ErrInvalidSample)

	require.NoError(t, app2.Commit())

	q, err := db.Querier(0, 200)
	require.NoError(t, err)

	res := query(t, q, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

	require.Equal(t, map[string][]chunks.Sample{
		labels.FromStrings("a", "b").String(): {
			sample{t: 123, f: 0},
			sample{t: 124, f: 1},
			sample{t: 125, f: 0},
			sample{t: 133, f: 1},
			sample{t: 143, f: 2},
		},
	}, res)
}

func TestAppendEmptyLabelsIgnored(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app1 := db.Appender(ctx)

	ref1, err := app1.Append(0, labels.FromStrings("a", "b"), 123, 0)
	require.NoError(t, err)

	// Add with empty label.
	ref2, err := app1.Append(0, labels.FromStrings("a", "b", "c", ""), 124, 0)
	require.NoError(t, err)

	// Should be the same series.
	require.Equal(t, ref1, ref2)

	err = app1.Commit()
	require.NoError(t, err)
}

func TestDeleteSimple(t *testing.T) {
	const numSamples int64 = 10

	cases := []struct {
		Intervals tombstones.Intervals
		remaint   []int64
	}{
		{
			Intervals: tombstones.Intervals{{Mint: 0, Maxt: 3}},
			remaint:   []int64{4, 5, 6, 7, 8, 9},
		},
		{
			Intervals: tombstones.Intervals{{Mint: 1, Maxt: 3}},
			remaint:   []int64{0, 4, 5, 6, 7, 8, 9},
		},
		{
			Intervals: tombstones.Intervals{{Mint: 1, Maxt: 3}, {Mint: 4, Maxt: 7}},
			remaint:   []int64{0, 8, 9},
		},
		{
			Intervals: tombstones.Intervals{{Mint: 1, Maxt: 3}, {Mint: 4, Maxt: 700}},
			remaint:   []int64{0},
		},
		{ // This case is to ensure that labels and symbols are deleted.
			Intervals: tombstones.Intervals{{Mint: 0, Maxt: 9}},
			remaint:   []int64{},
		},
	}

Outer:
	for _, c := range cases {
		db := openTestDB(t, nil, nil)
		defer func() {
			require.NoError(t, db.Close())
		}()

		ctx := context.Background()
		app := db.Appender(ctx)

		smpls := make([]float64, numSamples)
		for i := int64(0); i < numSamples; i++ {
			smpls[i] = rand.Float64()
			app.Append(0, labels.FromStrings("a", "b"), i, smpls[i])
		}

		require.NoError(t, app.Commit())

		// TODO(gouthamve): Reset the tombstones somehow.
		// Delete the ranges.
		for _, r := range c.Intervals {
			require.NoError(t, db.Delete(ctx, r.Mint, r.Maxt, labels.MustNewMatcher(labels.MatchEqual, "a", "b")))
		}

		// Compare the result.
		q, err := db.Querier(0, numSamples)
		require.NoError(t, err)

		res := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

		expSamples := make([]chunks.Sample, 0, len(c.remaint))
		for _, ts := range c.remaint {
			expSamples = append(expSamples, sample{ts, smpls[ts], nil, nil})
		}

		expss := newMockSeriesSet([]storage.Series{
			storage.NewListSeries(labels.FromStrings("a", "b"), expSamples),
		})

		for {
			eok, rok := expss.Next(), res.Next()
			require.Equal(t, eok, rok)

			if !eok {
				require.Empty(t, res.Warnings())
				continue Outer
			}
			sexp := expss.At()
			sres := res.At()

			require.Equal(t, sexp.Labels(), sres.Labels())

			smplExp, errExp := storage.ExpandSamples(sexp.Iterator(nil), nil)
			smplRes, errRes := storage.ExpandSamples(sres.Iterator(nil), nil)

			require.Equal(t, errExp, errRes)
			require.Equal(t, smplExp, smplRes)
		}
	}
}

func TestAmendHistogramDatapointCausesError(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)
	_, err := app.Append(0, labels.FromStrings("a", "b"), 0, 0)
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	app = db.Appender(ctx)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 0, 0)
	require.NoError(t, err)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 0, 1)
	require.Equal(t, storage.ErrDuplicateSampleForTimestamp, err)
	require.NoError(t, app.Rollback())

	h := histogram.Histogram{
		Schema:        3,
		Count:         52,
		Sum:           2.7,
		ZeroThreshold: 0.1,
		ZeroCount:     42,
		PositiveSpans: []histogram.Span{
			{Offset: 0, Length: 4},
			{Offset: 10, Length: 3},
		},
		PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
	}
	fh := h.ToFloat(nil)

	app = db.Appender(ctx)
	_, err = app.AppendHistogram(0, labels.FromStrings("a", "c"), 0, h.Copy(), nil)
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	app = db.Appender(ctx)
	_, err = app.AppendHistogram(0, labels.FromStrings("a", "c"), 0, h.Copy(), nil)
	require.NoError(t, err)
	h.Schema = 2
	_, err = app.AppendHistogram(0, labels.FromStrings("a", "c"), 0, h.Copy(), nil)
	require.Equal(t, storage.ErrDuplicateSampleForTimestamp, err)
	require.NoError(t, app.Rollback())

	// Float histogram.
	app = db.Appender(ctx)
	_, err = app.AppendHistogram(0, labels.FromStrings("a", "d"), 0, nil, fh.Copy())
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	app = db.Appender(ctx)
	_, err = app.AppendHistogram(0, labels.FromStrings("a", "d"), 0, nil, fh.Copy())
	require.NoError(t, err)
	fh.Schema = 2
	_, err = app.AppendHistogram(0, labels.FromStrings("a", "d"), 0, nil, fh.Copy())
	require.Equal(t, storage.ErrDuplicateSampleForTimestamp, err)
	require.NoError(t, app.Rollback())
}

func TestDuplicateNaNDatapointNoAmendError(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)
	_, err := app.Append(0, labels.FromStrings("a", "b"), 0, math.NaN())
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	app = db.Appender(ctx)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 0, math.NaN())
	require.NoError(t, err)
}

func TestNonDuplicateNaNDatapointsCausesAmendError(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)
	_, err := app.Append(0, labels.FromStrings("a", "b"), 0, math.Float64frombits(0x7ff0000000000001))
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	app = db.Appender(ctx)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 0, math.Float64frombits(0x7ff0000000000002))
	require.Equal(t, storage.ErrDuplicateSampleForTimestamp, err)
}

func TestEmptyLabelsetCausesError(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)
	_, err := app.Append(0, labels.Labels{}, 0, 0)
	require.Error(t, err)
	require.Equal(t, "empty labelset: invalid sample", err.Error())
}

func TestSkippingInvalidValuesInSameTxn(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	// Append AmendedValue.
	ctx := context.Background()
	app := db.Appender(ctx)
	_, err := app.Append(0, labels.FromStrings("a", "b"), 0, 1)
	require.NoError(t, err)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 0, 2)
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	// Make sure the right value is stored.
	q, err := db.Querier(0, 10)
	require.NoError(t, err)

	ssMap := query(t, q, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

	require.Equal(t, map[string][]chunks.Sample{
		labels.New(labels.Label{Name: "a", Value: "b"}).String(): {sample{0, 1, nil, nil}},
	}, ssMap)

	// Append Out of Order Value.
	app = db.Appender(ctx)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 10, 3)
	require.NoError(t, err)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 7, 5)
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	q, err = db.Querier(0, 10)
	require.NoError(t, err)

	ssMap = query(t, q, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

	require.Equal(t, map[string][]chunks.Sample{
		labels.New(labels.Label{Name: "a", Value: "b"}).String(): {sample{0, 1, nil, nil}, sample{10, 3, nil, nil}},
	}, ssMap)
}

func TestDB_Snapshot(t *testing.T) {
	db := openTestDB(t, nil, nil)

	// append data
	ctx := context.Background()
	app := db.Appender(ctx)
	mint := int64(1414141414000)
	for i := 0; i < 1000; i++ {
		_, err := app.Append(0, labels.FromStrings("foo", "bar"), mint+int64(i), 1.0)
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	// create snapshot
	snap := t.TempDir()
	require.NoError(t, db.Snapshot(snap, true))
	require.NoError(t, db.Close())

	// reopen DB from snapshot
	db, err := Open(snap, nil, nil, nil, nil)
	require.NoError(t, err)
	defer func() { require.NoError(t, db.Close()) }()

	querier, err := db.Querier(mint, mint+1000)
	require.NoError(t, err)
	defer func() { require.NoError(t, querier.Close()) }()

	// sum values
	seriesSet := querier.Select(context.Background(), false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	var series chunkenc.Iterator
	sum := 0.0
	for seriesSet.Next() {
		series = seriesSet.At().Iterator(series)
		for series.Next() == chunkenc.ValFloat {
			_, v := series.At()
			sum += v
		}
		require.NoError(t, series.Err())
	}
	require.NoError(t, seriesSet.Err())
	require.Empty(t, seriesSet.Warnings())
	require.Equal(t, 1000.0, sum)
}

// TestDB_Snapshot_ChunksOutsideOfCompactedRange ensures that a snapshot removes chunks samples
// that are outside the set block time range.
// See https://github.com/prometheus/prometheus/issues/5105
func TestDB_Snapshot_ChunksOutsideOfCompactedRange(t *testing.T) {
	db := openTestDB(t, nil, nil)

	ctx := context.Background()
	app := db.Appender(ctx)
	mint := int64(1414141414000)
	for i := 0; i < 1000; i++ {
		_, err := app.Append(0, labels.FromStrings("foo", "bar"), mint+int64(i), 1.0)
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	snap := t.TempDir()

	// Hackingly introduce "race", by having lower max time then maxTime in last chunk.
	db.head.maxTime.Sub(10)

	require.NoError(t, db.Snapshot(snap, true))
	require.NoError(t, db.Close())

	// Reopen DB from snapshot.
	db, err := Open(snap, nil, nil, nil, nil)
	require.NoError(t, err)
	defer func() { require.NoError(t, db.Close()) }()

	querier, err := db.Querier(mint, mint+1000)
	require.NoError(t, err)
	defer func() { require.NoError(t, querier.Close()) }()

	// Sum values.
	seriesSet := querier.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	var series chunkenc.Iterator
	sum := 0.0
	for seriesSet.Next() {
		series = seriesSet.At().Iterator(series)
		for series.Next() == chunkenc.ValFloat {
			_, v := series.At()
			sum += v
		}
		require.NoError(t, series.Err())
	}
	require.NoError(t, seriesSet.Err())
	require.Empty(t, seriesSet.Warnings())

	// Since we snapshotted with MaxTime - 10, so expect 10 less samples.
	require.Equal(t, 1000.0-10, sum)
}

func TestDB_SnapshotWithDelete(t *testing.T) {
	const numSamples int64 = 10

	db := openTestDB(t, nil, nil)
	defer func() { require.NoError(t, db.Close()) }()

	ctx := context.Background()
	app := db.Appender(ctx)

	smpls := make([]float64, numSamples)
	for i := int64(0); i < numSamples; i++ {
		smpls[i] = rand.Float64()
		app.Append(0, labels.FromStrings("a", "b"), i, smpls[i])
	}

	require.NoError(t, app.Commit())
	cases := []struct {
		intervals tombstones.Intervals
		remaint   []int64
	}{
		{
			intervals: tombstones.Intervals{{Mint: 1, Maxt: 3}, {Mint: 4, Maxt: 7}},
			remaint:   []int64{0, 8, 9},
		},
	}

Outer:
	for _, c := range cases {
		// TODO(gouthamve): Reset the tombstones somehow.
		// Delete the ranges.
		for _, r := range c.intervals {
			require.NoError(t, db.Delete(ctx, r.Mint, r.Maxt, labels.MustNewMatcher(labels.MatchEqual, "a", "b")))
		}

		// create snapshot
		snap := t.TempDir()

		require.NoError(t, db.Snapshot(snap, true))

		// reopen DB from snapshot
		newDB, err := Open(snap, nil, nil, nil, nil)
		require.NoError(t, err)
		defer func() { require.NoError(t, newDB.Close()) }()

		// Compare the result.
		q, err := newDB.Querier(0, numSamples)
		require.NoError(t, err)
		defer func() { require.NoError(t, q.Close()) }()

		res := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

		expSamples := make([]chunks.Sample, 0, len(c.remaint))
		for _, ts := range c.remaint {
			expSamples = append(expSamples, sample{ts, smpls[ts], nil, nil})
		}

		expss := newMockSeriesSet([]storage.Series{
			storage.NewListSeries(labels.FromStrings("a", "b"), expSamples),
		})

		if len(expSamples) == 0 {
			require.False(t, res.Next())
			continue
		}

		for {
			eok, rok := expss.Next(), res.Next()
			require.Equal(t, eok, rok)

			if !eok {
				require.Empty(t, res.Warnings())
				continue Outer
			}
			sexp := expss.At()
			sres := res.At()

			require.Equal(t, sexp.Labels(), sres.Labels())

			smplExp, errExp := storage.ExpandSamples(sexp.Iterator(nil), nil)
			smplRes, errRes := storage.ExpandSamples(sres.Iterator(nil), nil)

			require.Equal(t, errExp, errRes)
			require.Equal(t, smplExp, smplRes)
		}
	}
}

func TestDB_e2e(t *testing.T) {
	const (
		numDatapoints = 1000
		numRanges     = 1000
		timeInterval  = int64(3)
	)
	// Create 8 series with 1000 data-points of different ranges and run queries.
	lbls := [][]labels.Label{
		{
			{Name: "a", Value: "b"},
			{Name: "instance", Value: "localhost:9090"},
			{Name: "job", Value: "prometheus"},
		},
		{
			{Name: "a", Value: "b"},
			{Name: "instance", Value: "127.0.0.1:9090"},
			{Name: "job", Value: "prometheus"},
		},
		{
			{Name: "a", Value: "b"},
			{Name: "instance", Value: "127.0.0.1:9090"},
			{Name: "job", Value: "prom-k8s"},
		},
		{
			{Name: "a", Value: "b"},
			{Name: "instance", Value: "localhost:9090"},
			{Name: "job", Value: "prom-k8s"},
		},
		{
			{Name: "a", Value: "c"},
			{Name: "instance", Value: "localhost:9090"},
			{Name: "job", Value: "prometheus"},
		},
		{
			{Name: "a", Value: "c"},
			{Name: "instance", Value: "127.0.0.1:9090"},
			{Name: "job", Value: "prometheus"},
		},
		{
			{Name: "a", Value: "c"},
			{Name: "instance", Value: "127.0.0.1:9090"},
			{Name: "job", Value: "prom-k8s"},
		},
		{
			{Name: "a", Value: "c"},
			{Name: "instance", Value: "localhost:9090"},
			{Name: "job", Value: "prom-k8s"},
		},
	}

	seriesMap := map[string][]chunks.Sample{}
	for _, l := range lbls {
		seriesMap[labels.New(l...).String()] = []chunks.Sample{}
	}

	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)

	for _, l := range lbls {
		lset := labels.New(l...)
		series := []chunks.Sample{}

		ts := rand.Int63n(300)
		for i := 0; i < numDatapoints; i++ {
			v := rand.Float64()

			series = append(series, sample{ts, v, nil, nil})

			_, err := app.Append(0, lset, ts, v)
			require.NoError(t, err)

			ts += rand.Int63n(timeInterval) + 1
		}

		seriesMap[lset.String()] = series
	}

	require.NoError(t, app.Commit())

	// Query each selector on 1000 random time-ranges.
	queries := []struct {
		ms []*labels.Matcher
	}{
		{
			ms: []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "a", "b")},
		},
		{
			ms: []*labels.Matcher{
				labels.MustNewMatcher(labels.MatchEqual, "a", "b"),
				labels.MustNewMatcher(labels.MatchEqual, "job", "prom-k8s"),
			},
		},
		{
			ms: []*labels.Matcher{
				labels.MustNewMatcher(labels.MatchEqual, "a", "c"),
				labels.MustNewMatcher(labels.MatchEqual, "instance", "localhost:9090"),
				labels.MustNewMatcher(labels.MatchEqual, "job", "prometheus"),
			},
		},
		// TODO: Add Regexp Matchers.
	}

	for _, qry := range queries {
		matched := labels.Slice{}
		for _, l := range lbls {
			s := labels.Selector(qry.ms)
			ls := labels.New(l...)
			if s.Matches(ls) {
				matched = append(matched, ls)
			}
		}

		sort.Sort(matched)

		for i := 0; i < numRanges; i++ {
			mint := rand.Int63n(300)
			maxt := mint + rand.Int63n(timeInterval*int64(numDatapoints))

			expected := map[string][]chunks.Sample{}

			// Build the mockSeriesSet.
			for _, m := range matched {
				smpls := boundedSamples(seriesMap[m.String()], mint, maxt)
				if len(smpls) > 0 {
					expected[m.String()] = smpls
				}
			}

			q, err := db.Querier(mint, maxt)
			require.NoError(t, err)

			ss := q.Select(ctx, false, nil, qry.ms...)
			result := map[string][]chunks.Sample{}

			for ss.Next() {
				x := ss.At()

				smpls, err := storage.ExpandSamples(x.Iterator(nil), newSample)
				require.NoError(t, err)

				if len(smpls) > 0 {
					result[x.Labels().String()] = smpls
				}
			}

			require.NoError(t, ss.Err())
			require.Empty(t, ss.Warnings())
			require.Equal(t, expected, result)

			q.Close()
		}
	}
}

func TestWALFlushedOnDBClose(t *testing.T) {
	db := openTestDB(t, nil, nil)

	dirDb := db.Dir()

	lbls := labels.FromStrings("labelname", "labelvalue")

	ctx := context.Background()
	app := db.Appender(ctx)
	_, err := app.Append(0, lbls, 0, 1)
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	require.NoError(t, db.Close())

	db, err = Open(dirDb, nil, nil, nil, nil)
	require.NoError(t, err)
	defer func() { require.NoError(t, db.Close()) }()

	q, err := db.Querier(0, 1)
	require.NoError(t, err)

	values, ws, err := q.LabelValues(ctx, "labelname")
	require.NoError(t, err)
	require.Empty(t, ws)
	require.Equal(t, []string{"labelvalue"}, values)
}

func TestWALSegmentSizeOptions(t *testing.T) {
	tests := map[int]func(dbdir string, segmentSize int){
		// Default Wal Size.
		0: func(dbDir string, segmentSize int) {
			filesAndDir, err := os.ReadDir(filepath.Join(dbDir, "wal"))
			require.NoError(t, err)
			files := []os.FileInfo{}
			for _, f := range filesAndDir {
				if !f.IsDir() {
					fi, err := f.Info()
					require.NoError(t, err)
					files = append(files, fi)
				}
			}
			// All the full segment files (all but the last) should match the segment size option.
			for _, f := range files[:len(files)-1] {
				require.Equal(t, int64(DefaultOptions().WALSegmentSize), f.Size(), "WAL file size doesn't match WALSegmentSize option, filename: %v", f.Name())
			}
			lastFile := files[len(files)-1]
			require.Greater(t, int64(DefaultOptions().WALSegmentSize), lastFile.Size(), "last WAL file size is not smaller than the WALSegmentSize option, filename: %v", lastFile.Name())
		},
		// Custom Wal Size.
		2 * 32 * 1024: func(dbDir string, segmentSize int) {
			filesAndDir, err := os.ReadDir(filepath.Join(dbDir, "wal"))
			require.NoError(t, err)
			files := []os.FileInfo{}
			for _, f := range filesAndDir {
				if !f.IsDir() {
					fi, err := f.Info()
					require.NoError(t, err)
					files = append(files, fi)
				}
			}
			require.NotEmpty(t, files, "current WALSegmentSize should result in more than a single WAL file.")
			// All the full segment files (all but the last) should match the segment size option.
			for _, f := range files[:len(files)-1] {
				require.Equal(t, int64(segmentSize), f.Size(), "WAL file size doesn't match WALSegmentSize option, filename: %v", f.Name())
			}
			lastFile := files[len(files)-1]
			require.Greater(t, int64(segmentSize), lastFile.Size(), "last WAL file size is not smaller than the WALSegmentSize option, filename: %v", lastFile.Name())
		},
		// Wal disabled.
		-1: func(dbDir string, segmentSize int) {
			// Check that WAL dir is not there.
			_, err := os.Stat(filepath.Join(dbDir, "wal"))
			require.Error(t, err)
			// Check that there is chunks dir.
			_, err = os.Stat(mmappedChunksDir(dbDir))
			require.NoError(t, err)
		},
	}
	for segmentSize, testFunc := range tests {
		t.Run(fmt.Sprintf("WALSegmentSize %d test", segmentSize), func(t *testing.T) {
			opts := DefaultOptions()
			opts.WALSegmentSize = segmentSize
			db := openTestDB(t, opts, nil)

			for i := int64(0); i < 155; i++ {
				app := db.Appender(context.Background())
				ref, err := app.Append(0, labels.FromStrings("wal"+fmt.Sprintf("%d", i), "size"), i, rand.Float64())
				require.NoError(t, err)
				for j := int64(1); j <= 78; j++ {
					_, err := app.Append(ref, labels.EmptyLabels(), i+j, rand.Float64())
					require.NoError(t, err)
				}
				require.NoError(t, app.Commit())
			}

			dbDir := db.Dir()
			require.NoError(t, db.Close())
			testFunc(dbDir, opts.WALSegmentSize)
		})
	}
}

// https://github.com/prometheus/prometheus/issues/9846
// https://github.com/prometheus/prometheus/issues/9859
func TestWALReplayRaceOnSamplesLoggedBeforeSeries(t *testing.T) {
	const (
		numRuns                        = 1
		numSamplesBeforeSeriesCreation = 1000
	)

	// We test both with few and many samples appended after series creation. If samples are < 120 then there's no
	// mmap-ed chunk, otherwise there's at least 1 mmap-ed chunk when replaying the WAL.
	for _, numSamplesAfterSeriesCreation := range []int{1, 1000} {
		for run := 1; run <= numRuns; run++ {
			t.Run(fmt.Sprintf("samples after series creation = %d, run = %d", numSamplesAfterSeriesCreation, run), func(t *testing.T) {
				testWALReplayRaceOnSamplesLoggedBeforeSeries(t, numSamplesBeforeSeriesCreation, numSamplesAfterSeriesCreation)
			})
		}
	}
}

func testWALReplayRaceOnSamplesLoggedBeforeSeries(t *testing.T, numSamplesBeforeSeriesCreation, numSamplesAfterSeriesCreation int) {
	const numSeries = 1000

	db := openTestDB(t, nil, nil)
	db.DisableCompactions()

	for seriesRef := 1; seriesRef <= numSeries; seriesRef++ {
		// Log samples before the series is logged to the WAL.
		var enc record.Encoder
		var samples []record.RefSample

		for ts := 0; ts < numSamplesBeforeSeriesCreation; ts++ {
			samples = append(samples, record.RefSample{
				Ref: chunks.HeadSeriesRef(uint64(seriesRef)),
				T:   int64(ts),
				V:   float64(ts),
			})
		}

		err := db.Head().wal.Log(enc.Samples(samples, nil))
		require.NoError(t, err)

		// Add samples via appender so that they're logged after the series in the WAL.
		app := db.Appender(context.Background())
		lbls := labels.FromStrings("series_id", strconv.Itoa(seriesRef))

		for ts := numSamplesBeforeSeriesCreation; ts < numSamplesBeforeSeriesCreation+numSamplesAfterSeriesCreation; ts++ {
			_, err := app.Append(0, lbls, int64(ts), float64(ts))
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
	}

	require.NoError(t, db.Close())

	// Reopen the DB, replaying the WAL.
	reopenDB, err := Open(db.Dir(), log.NewLogfmtLogger(os.Stderr), nil, nil, nil)
	require.NoError(t, err)
	t.Cleanup(func() {
		require.NoError(t, reopenDB.Close())
	})

	// Query back chunks for all series.
	q, err := reopenDB.ChunkQuerier(math.MinInt64, math.MaxInt64)
	require.NoError(t, err)

	set := q.Select(context.Background(), false, nil, labels.MustNewMatcher(labels.MatchRegexp, "series_id", ".+"))
	actualSeries := 0
	var chunksIt chunks.Iterator

	for set.Next() {
		actualSeries++
		actualChunks := 0

		chunksIt = set.At().Iterator(chunksIt)
		for chunksIt.Next() {
			actualChunks++
		}
		require.NoError(t, chunksIt.Err())

		// We expect 1 chunk every 120 samples after series creation.
		require.Equalf(t, (numSamplesAfterSeriesCreation/120)+1, actualChunks, "series: %s", set.At().Labels().String())
	}

	require.NoError(t, set.Err())
	require.Equal(t, numSeries, actualSeries)
}

func TestTombstoneClean(t *testing.T) {
	const numSamples int64 = 10

	db := openTestDB(t, nil, nil)

	ctx := context.Background()
	app := db.Appender(ctx)

	smpls := make([]float64, numSamples)
	for i := int64(0); i < numSamples; i++ {
		smpls[i] = rand.Float64()
		app.Append(0, labels.FromStrings("a", "b"), i, smpls[i])
	}

	require.NoError(t, app.Commit())
	cases := []struct {
		intervals tombstones.Intervals
		remaint   []int64
	}{
		{
			intervals: tombstones.Intervals{{Mint: 1, Maxt: 3}, {Mint: 4, Maxt: 7}},
			remaint:   []int64{0, 8, 9},
		},
	}

	for _, c := range cases {
		// Delete the ranges.

		// Create snapshot.
		snap := t.TempDir()
		require.NoError(t, db.Snapshot(snap, true))
		require.NoError(t, db.Close())

		// Reopen DB from snapshot.
		db, err := Open(snap, nil, nil, nil, nil)
		require.NoError(t, err)
		defer db.Close()

		for _, r := range c.intervals {
			require.NoError(t, db.Delete(ctx, r.Mint, r.Maxt, labels.MustNewMatcher(labels.MatchEqual, "a", "b")))
		}

		// All of the setup for THIS line.
		require.NoError(t, db.CleanTombstones())

		// Compare the result.
		q, err := db.Querier(0, numSamples)
		require.NoError(t, err)
		defer q.Close()

		res := q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

		expSamples := make([]chunks.Sample, 0, len(c.remaint))
		for _, ts := range c.remaint {
			expSamples = append(expSamples, sample{ts, smpls[ts], nil, nil})
		}

		expss := newMockSeriesSet([]storage.Series{
			storage.NewListSeries(labels.FromStrings("a", "b"), expSamples),
		})

		if len(expSamples) == 0 {
			require.False(t, res.Next())
			continue
		}

		for {
			eok, rok := expss.Next(), res.Next()
			require.Equal(t, eok, rok)

			if !eok {
				break
			}
			sexp := expss.At()
			sres := res.At()

			require.Equal(t, sexp.Labels(), sres.Labels())

			smplExp, errExp := storage.ExpandSamples(sexp.Iterator(nil), nil)
			smplRes, errRes := storage.ExpandSamples(sres.Iterator(nil), nil)

			require.Equal(t, errExp, errRes)
			require.Equal(t, smplExp, smplRes)
		}
		require.Empty(t, res.Warnings())

		for _, b := range db.Blocks() {
			require.Equal(t, tombstones.NewMemTombstones(), b.tombstones)
		}
	}
}

// TestTombstoneCleanResultEmptyBlock tests that a TombstoneClean that results in empty blocks (no timeseries)
// will also delete the resultant block.
func TestTombstoneCleanResultEmptyBlock(t *testing.T) {
	numSamples := int64(10)

	db := openTestDB(t, nil, nil)

	ctx := context.Background()
	app := db.Appender(ctx)

	smpls := make([]float64, numSamples)
	for i := int64(0); i < numSamples; i++ {
		smpls[i] = rand.Float64()
		app.Append(0, labels.FromStrings("a", "b"), i, smpls[i])
	}

	require.NoError(t, app.Commit())
	// Interval should cover the whole block.
	intervals := tombstones.Intervals{{Mint: 0, Maxt: numSamples}}

	// Create snapshot.
	snap := t.TempDir()
	require.NoError(t, db.Snapshot(snap, true))
	require.NoError(t, db.Close())

	// Reopen DB from snapshot.
	db, err := Open(snap, nil, nil, nil, nil)
	require.NoError(t, err)
	defer db.Close()

	// Create tombstones by deleting all samples.
	for _, r := range intervals {
		require.NoError(t, db.Delete(ctx, r.Mint, r.Maxt, labels.MustNewMatcher(labels.MatchEqual, "a", "b")))
	}

	require.NoError(t, db.CleanTombstones())

	// After cleaning tombstones that covers the entire block, no blocks should be left behind.
	actualBlockDirs, err := blockDirs(db.dir)
	require.NoError(t, err)
	require.Empty(t, actualBlockDirs)
}

// TestTombstoneCleanFail tests that a failing TombstoneClean doesn't leave any blocks behind.
// When TombstoneClean errors the original block that should be rebuilt doesn't get deleted so
// if TombstoneClean leaves any blocks behind these will overlap.
func TestTombstoneCleanFail(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	var oldBlockDirs []string

	// Create some blocks pending for compaction.
	// totalBlocks should be >=2 so we have enough blocks to trigger compaction failure.
	totalBlocks := 2
	for i := 0; i < totalBlocks; i++ {
		blockDir := createBlock(t, db.Dir(), genSeries(1, 1, int64(i), int64(i)+1))
		block, err := OpenBlock(nil, blockDir, nil)
		require.NoError(t, err)
		// Add some fake tombstones to trigger the compaction.
		tomb := tombstones.NewMemTombstones()
		tomb.AddInterval(0, tombstones.Interval{Mint: int64(i), Maxt: int64(i) + 1})
		block.tombstones = tomb

		db.blocks = append(db.blocks, block)
		oldBlockDirs = append(oldBlockDirs, blockDir)
	}

	// Initialize the mockCompactorFailing with a room for a single compaction iteration.
	// mockCompactorFailing will fail on the second iteration so we can check if the cleanup works as expected.
	db.compactor = &mockCompactorFailing{
		t:      t,
		blocks: db.blocks,
		max:    totalBlocks + 1,
	}

	// The compactor should trigger a failure here.
	require.Error(t, db.CleanTombstones())

	// Now check that the CleanTombstones replaced the old block even after a failure.
	actualBlockDirs, err := blockDirs(db.dir)
	require.NoError(t, err)
	// Only one block should have been replaced by a new block.
	require.Equal(t, len(oldBlockDirs), len(actualBlockDirs))
	require.Len(t, intersection(oldBlockDirs, actualBlockDirs), len(actualBlockDirs)-1)
}

// TestTombstoneCleanRetentionLimitsRace tests that a CleanTombstones operation
// and retention limit policies, when triggered at the same time,
// won't race against each other.
func TestTombstoneCleanRetentionLimitsRace(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping test in short mode.")
	}

	opts := DefaultOptions()
	var wg sync.WaitGroup

	// We want to make sure that a race doesn't happen when a normal reload and a CleanTombstones()
	// reload try to delete the same block. Without the correct lock placement, it can happen if a
	// block is marked for deletion due to retention limits and also has tombstones to be cleaned at
	// the same time.
	//
	// That is something tricky to trigger, so let's try several times just to make sure.
	for i := 0; i < 20; i++ {
		t.Run(fmt.Sprintf("iteration%d", i), func(t *testing.T) {
			db := openTestDB(t, opts, nil)
			totalBlocks := 20
			dbDir := db.Dir()
			// Generate some blocks with old mint (near epoch).
			for j := 0; j < totalBlocks; j++ {
				blockDir := createBlock(t, dbDir, genSeries(10, 1, int64(j), int64(j)+1))
				block, err := OpenBlock(nil, blockDir, nil)
				require.NoError(t, err)
				// Cover block with tombstones so it can be deleted with CleanTombstones() as well.
				tomb := tombstones.NewMemTombstones()
				tomb.AddInterval(0, tombstones.Interval{Mint: int64(j), Maxt: int64(j) + 1})
				block.tombstones = tomb

				db.blocks = append(db.blocks, block)
			}

			wg.Add(2)
			// Run reload and CleanTombstones together, with a small time window randomization
			go func() {
				defer wg.Done()
				time.Sleep(time.Duration(rand.Float64() * 100 * float64(time.Millisecond)))
				require.NoError(t, db.reloadBlocks())
			}()
			go func() {
				defer wg.Done()
				time.Sleep(time.Duration(rand.Float64() * 100 * float64(time.Millisecond)))
				require.NoError(t, db.CleanTombstones())
			}()

			wg.Wait()

			require.NoError(t, db.Close())
		})
	}
}

func intersection(oldBlocks, actualBlocks []string) (intersection []string) {
	hash := make(map[string]bool)
	for _, e := range oldBlocks {
		hash[e] = true
	}
	for _, e := range actualBlocks {
		// If block present in the hashmap then append intersection list.
		if hash[e] {
			intersection = append(intersection, e)
		}
	}
	return
}

// mockCompactorFailing creates a new empty block on every write and fails when reached the max allowed total.
// For CompactOOO, it always fails.
type mockCompactorFailing struct {
	t      *testing.T
	blocks []*Block
	max    int
}

func (*mockCompactorFailing) Plan(string) ([]string, error) {
	return nil, nil
}

func (c *mockCompactorFailing) Write(dest string, _ BlockReader, _, _ int64, _ *BlockMeta) (ulid.ULID, error) {
	if len(c.blocks) >= c.max {
		return ulid.ULID{}, fmt.Errorf("the compactor already did the maximum allowed blocks so it is time to fail")
	}

	block, err := OpenBlock(nil, createBlock(c.t, dest, genSeries(1, 1, 0, 1)), nil)
	require.NoError(c.t, err)
	require.NoError(c.t, block.Close()) // Close block as we won't be using anywhere.
	c.blocks = append(c.blocks, block)

	// Now check that all expected blocks are actually persisted on disk.
	// This way we make sure that the we have some blocks that are supposed to be removed.
	var expectedBlocks []string
	for _, b := range c.blocks {
		expectedBlocks = append(expectedBlocks, filepath.Join(dest, b.Meta().ULID.String()))
	}
	actualBlockDirs, err := blockDirs(dest)
	require.NoError(c.t, err)

	require.Equal(c.t, expectedBlocks, actualBlockDirs)

	return block.Meta().ULID, nil
}

func (*mockCompactorFailing) Compact(string, []string, []*Block) (ulid.ULID, error) {
	return ulid.ULID{}, nil
}

func (*mockCompactorFailing) CompactOOO(string, *OOOCompactionHead) (result []ulid.ULID, err error) {
	return nil, fmt.Errorf("mock compaction failing CompactOOO")
}

func TestTimeRetention(t *testing.T) {
	db := openTestDB(t, nil, []int64{1000})
	defer func() {
		require.NoError(t, db.Close())
	}()

	blocks := []*BlockMeta{
		{MinTime: 500, MaxTime: 900}, // Oldest block
		{MinTime: 1000, MaxTime: 1500},
		{MinTime: 1500, MaxTime: 2000}, // Newest Block
	}

	for _, m := range blocks {
		createBlock(t, db.Dir(), genSeries(10, 10, m.MinTime, m.MaxTime))
	}

	require.NoError(t, db.reloadBlocks())           // Reload the db to register the new blocks.
	require.Equal(t, len(blocks), len(db.Blocks())) // Ensure all blocks are registered.

	db.opts.RetentionDuration = blocks[2].MaxTime - blocks[1].MinTime
	require.NoError(t, db.reloadBlocks())

	expBlocks := blocks[1:]
	actBlocks := db.Blocks()

	require.Equal(t, 1, int(prom_testutil.ToFloat64(db.metrics.timeRetentionCount)), "metric retention count mismatch")
	require.Equal(t, len(expBlocks), len(actBlocks))
	require.Equal(t, expBlocks[0].MaxTime, actBlocks[0].meta.MaxTime)
	require.Equal(t, expBlocks[len(expBlocks)-1].MaxTime, actBlocks[len(actBlocks)-1].meta.MaxTime)
}

func TestRetentionDurationMetric(t *testing.T) {
	db := openTestDB(t, &Options{
		RetentionDuration: 1000,
	}, []int64{100})
	defer func() {
		require.NoError(t, db.Close())
	}()

	expRetentionDuration := 1.0
	actRetentionDuration := prom_testutil.ToFloat64(db.metrics.retentionDuration)
	require.Equal(t, expRetentionDuration, actRetentionDuration, "metric retention duration mismatch")
}

func TestSizeRetention(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 100
	db := openTestDB(t, opts, []int64{100})
	defer func() {
		require.NoError(t, db.Close())
	}()

	blocks := []*BlockMeta{
		{MinTime: 100, MaxTime: 200}, // Oldest block
		{MinTime: 200, MaxTime: 300},
		{MinTime: 300, MaxTime: 400},
		{MinTime: 400, MaxTime: 500},
		{MinTime: 500, MaxTime: 600}, // Newest Block
	}

	for _, m := range blocks {
		createBlock(t, db.Dir(), genSeries(100, 10, m.MinTime, m.MaxTime))
	}

	headBlocks := []*BlockMeta{
		{MinTime: 700, MaxTime: 800},
	}

	// Add some data to the WAL.
	headApp := db.Head().Appender(context.Background())
	var aSeries labels.Labels
	var it chunkenc.Iterator
	for _, m := range headBlocks {
		series := genSeries(100, 10, m.MinTime, m.MaxTime+1)
		for _, s := range series {
			aSeries = s.Labels()
			it = s.Iterator(it)
			for it.Next() == chunkenc.ValFloat {
				tim, v := it.At()
				_, err := headApp.Append(0, s.Labels(), tim, v)
				require.NoError(t, err)
			}
			require.NoError(t, it.Err())
		}
	}
	require.NoError(t, headApp.Commit())
	db.Head().mmapHeadChunks()

	require.Eventually(t, func() bool {
		return db.Head().chunkDiskMapper.IsQueueEmpty()
	}, 2*time.Second, 100*time.Millisecond)

	// Test that registered size matches the actual disk size.
	require.NoError(t, db.reloadBlocks())                               // Reload the db to register the new db size.
	require.Equal(t, len(blocks), len(db.Blocks()))                     // Ensure all blocks are registered.
	blockSize := int64(prom_testutil.ToFloat64(db.metrics.blocksBytes)) // Use the actual internal metrics.
	walSize, err := db.Head().wal.Size()
	require.NoError(t, err)
	cdmSize, err := db.Head().chunkDiskMapper.Size()
	require.NoError(t, err)
	require.NotZero(t, cdmSize)
	// Expected size should take into account block size + WAL size + Head
	// chunks size
	expSize := blockSize + walSize + cdmSize
	actSize, err := fileutil.DirSize(db.Dir())
	require.NoError(t, err)
	require.Equal(t, expSize, actSize, "registered size doesn't match actual disk size")

	// Create a WAL checkpoint, and compare sizes.
	first, last, err := wlog.Segments(db.Head().wal.Dir())
	require.NoError(t, err)
	_, err = wlog.Checkpoint(log.NewNopLogger(), db.Head().wal, first, last-1, func(x chunks.HeadSeriesRef) bool { return false }, 0)
	require.NoError(t, err)
	blockSize = int64(prom_testutil.ToFloat64(db.metrics.blocksBytes)) // Use the actual internal metrics.
	walSize, err = db.Head().wal.Size()
	require.NoError(t, err)
	cdmSize, err = db.Head().chunkDiskMapper.Size()
	require.NoError(t, err)
	require.NotZero(t, cdmSize)
	expSize = blockSize + walSize + cdmSize
	actSize, err = fileutil.DirSize(db.Dir())
	require.NoError(t, err)
	require.Equal(t, expSize, actSize, "registered size doesn't match actual disk size")

	// Truncate Chunk Disk Mapper and compare sizes.
	require.NoError(t, db.Head().chunkDiskMapper.Truncate(900))
	cdmSize, err = db.Head().chunkDiskMapper.Size()
	require.NoError(t, err)
	require.NotZero(t, cdmSize)
	expSize = blockSize + walSize + cdmSize
	actSize, err = fileutil.DirSize(db.Dir())
	require.NoError(t, err)
	require.Equal(t, expSize, actSize, "registered size doesn't match actual disk size")

	// Add some out of order samples to check the size of WBL.
	headApp = db.Head().Appender(context.Background())
	for ts := int64(750); ts < 800; ts++ {
		_, err := headApp.Append(0, aSeries, ts, float64(ts))
		require.NoError(t, err)
	}
	require.NoError(t, headApp.Commit())

	walSize, err = db.Head().wal.Size()
	require.NoError(t, err)
	wblSize, err := db.Head().wbl.Size()
	require.NoError(t, err)
	require.NotZero(t, wblSize)
	cdmSize, err = db.Head().chunkDiskMapper.Size()
	require.NoError(t, err)
	expSize = blockSize + walSize + wblSize + cdmSize
	actSize, err = fileutil.DirSize(db.Dir())
	require.NoError(t, err)
	require.Equal(t, expSize, actSize, "registered size doesn't match actual disk size")

	// Decrease the max bytes limit so that a delete is triggered.
	// Check total size, total count and check that the oldest block was deleted.
	firstBlockSize := db.Blocks()[0].Size()
	sizeLimit := actSize - firstBlockSize
	db.opts.MaxBytes = sizeLimit          // Set the new db size limit one block smaller that the actual size.
	require.NoError(t, db.reloadBlocks()) // Reload the db to register the new db size.

	expBlocks := blocks[1:]
	actBlocks := db.Blocks()
	blockSize = int64(prom_testutil.ToFloat64(db.metrics.blocksBytes))
	walSize, err = db.Head().wal.Size()
	require.NoError(t, err)
	cdmSize, err = db.Head().chunkDiskMapper.Size()
	require.NoError(t, err)
	require.NotZero(t, cdmSize)
	// Expected size should take into account block size + WAL size + WBL size
	expSize = blockSize + walSize + wblSize + cdmSize
	actRetentionCount := int(prom_testutil.ToFloat64(db.metrics.sizeRetentionCount))
	actSize, err = fileutil.DirSize(db.Dir())
	require.NoError(t, err)

	require.Equal(t, 1, actRetentionCount, "metric retention count mismatch")
	require.Equal(t, expSize, actSize, "metric db size doesn't match actual disk size")
	require.LessOrEqual(t, expSize, sizeLimit, "actual size (%v) is expected to be less than or equal to limit (%v)", expSize, sizeLimit)
	require.Len(t, actBlocks, len(blocks)-1, "new block count should be decreased from:%v to:%v", len(blocks), len(blocks)-1)
	require.Equal(t, expBlocks[0].MaxTime, actBlocks[0].meta.MaxTime, "maxT mismatch of the first block")
	require.Equal(t, expBlocks[len(expBlocks)-1].MaxTime, actBlocks[len(actBlocks)-1].meta.MaxTime, "maxT mismatch of the last block")
}

func TestSizeRetentionMetric(t *testing.T) {
	cases := []struct {
		maxBytes    int64
		expMaxBytes int64
	}{
		{maxBytes: 1000, expMaxBytes: 1000},
		{maxBytes: 0, expMaxBytes: 0},
		{maxBytes: -1000, expMaxBytes: 0},
	}

	for _, c := range cases {
		db := openTestDB(t, &Options{
			MaxBytes: c.maxBytes,
		}, []int64{100})
		defer func() {
			require.NoError(t, db.Close())
		}()

		actMaxBytes := int64(prom_testutil.ToFloat64(db.metrics.maxBytes))
		require.Equal(t, c.expMaxBytes, actMaxBytes, "metric retention limit bytes mismatch")
	}
}

func TestNotMatcherSelectsLabelsUnsetSeries(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	labelpairs := []labels.Labels{
		labels.FromStrings("a", "abcd", "b", "abcde"),
		labels.FromStrings("labelname", "labelvalue"),
	}

	ctx := context.Background()
	app := db.Appender(ctx)
	for _, lbls := range labelpairs {
		_, err := app.Append(0, lbls, 0, 1)
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	cases := []struct {
		selector labels.Selector
		series   []labels.Labels
	}{{
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchNotEqual, "lname", "lvalue"),
		},
		series: labelpairs,
	}, {
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchEqual, "a", "abcd"),
			labels.MustNewMatcher(labels.MatchNotEqual, "b", "abcde"),
		},
		series: []labels.Labels{},
	}, {
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchEqual, "a", "abcd"),
			labels.MustNewMatcher(labels.MatchNotEqual, "b", "abc"),
		},
		series: []labels.Labels{labelpairs[0]},
	}, {
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchNotRegexp, "a", "abd.*"),
		},
		series: labelpairs,
	}, {
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchNotRegexp, "a", "abc.*"),
		},
		series: labelpairs[1:],
	}, {
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchNotRegexp, "c", "abd.*"),
		},
		series: labelpairs,
	}, {
		selector: labels.Selector{
			labels.MustNewMatcher(labels.MatchNotRegexp, "labelname", "labelvalue"),
		},
		series: labelpairs[:1],
	}}

	q, err := db.Querier(0, 10)
	require.NoError(t, err)
	defer func() { require.NoError(t, q.Close()) }()

	for _, c := range cases {
		ss := q.Select(ctx, false, nil, c.selector...)
		lres, _, ws, err := expandSeriesSet(ss)
		require.NoError(t, err)
		require.Empty(t, ws)
		require.Equal(t, c.series, lres)
	}
}

// expandSeriesSet returns the raw labels in the order they are retrieved from
// the series set and the samples keyed by Labels().String().
func expandSeriesSet(ss storage.SeriesSet) ([]labels.Labels, map[string][]sample, annotations.Annotations, error) {
	resultLabels := []labels.Labels{}
	resultSamples := map[string][]sample{}
	var it chunkenc.Iterator
	for ss.Next() {
		series := ss.At()
		samples := []sample{}
		it = series.Iterator(it)
		for it.Next() == chunkenc.ValFloat {
			t, v := it.At()
			samples = append(samples, sample{t: t, f: v})
		}
		resultLabels = append(resultLabels, series.Labels())
		resultSamples[series.Labels().String()] = samples
	}
	return resultLabels, resultSamples, ss.Warnings(), ss.Err()
}

func TestOverlappingBlocksDetectsAllOverlaps(t *testing.T) {
	// Create 10 blocks that does not overlap (0-10, 10-20, ..., 100-110) but in reverse order to ensure our algorithm
	// will handle that.
	metas := make([]BlockMeta, 11)
	for i := 10; i >= 0; i-- {
		metas[i] = BlockMeta{MinTime: int64(i * 10), MaxTime: int64((i + 1) * 10)}
	}

	require.Empty(t, OverlappingBlocks(metas), "we found unexpected overlaps")

	// Add overlapping blocks. We've to establish order again since we aren't interested
	// in trivial overlaps caused by unorderedness.
	add := func(ms ...BlockMeta) []BlockMeta {
		repl := append(append([]BlockMeta{}, metas...), ms...)
		sort.Slice(repl, func(i, j int) bool {
			return repl[i].MinTime < repl[j].MinTime
		})
		return repl
	}

	// o1 overlaps with 10-20.
	o1 := BlockMeta{MinTime: 15, MaxTime: 17}
	require.Equal(t, Overlaps{
		{Min: 15, Max: 17}: {metas[1], o1},
	}, OverlappingBlocks(add(o1)))

	// o2 overlaps with 20-30 and 30-40.
	o2 := BlockMeta{MinTime: 21, MaxTime: 31}
	require.Equal(t, Overlaps{
		{Min: 21, Max: 30}: {metas[2], o2},
		{Min: 30, Max: 31}: {o2, metas[3]},
	}, OverlappingBlocks(add(o2)))

	// o3a and o3b overlaps with 30-40 and each other.
	o3a := BlockMeta{MinTime: 33, MaxTime: 39}
	o3b := BlockMeta{MinTime: 34, MaxTime: 36}
	require.Equal(t, Overlaps{
		{Min: 34, Max: 36}: {metas[3], o3a, o3b},
	}, OverlappingBlocks(add(o3a, o3b)))

	// o4 is 1:1 overlap with 50-60.
	o4 := BlockMeta{MinTime: 50, MaxTime: 60}
	require.Equal(t, Overlaps{
		{Min: 50, Max: 60}: {metas[5], o4},
	}, OverlappingBlocks(add(o4)))

	// o5 overlaps with 60-70, 70-80 and 80-90.
	o5 := BlockMeta{MinTime: 61, MaxTime: 85}
	require.Equal(t, Overlaps{
		{Min: 61, Max: 70}: {metas[6], o5},
		{Min: 70, Max: 80}: {o5, metas[7]},
		{Min: 80, Max: 85}: {o5, metas[8]},
	}, OverlappingBlocks(add(o5)))

	// o6a overlaps with 90-100, 100-110 and o6b, o6b overlaps with 90-100 and o6a.
	o6a := BlockMeta{MinTime: 92, MaxTime: 105}
	o6b := BlockMeta{MinTime: 94, MaxTime: 99}
	require.Equal(t, Overlaps{
		{Min: 94, Max: 99}:   {metas[9], o6a, o6b},
		{Min: 100, Max: 105}: {o6a, metas[10]},
	}, OverlappingBlocks(add(o6a, o6b)))

	// All together.
	require.Equal(t, Overlaps{
		{Min: 15, Max: 17}: {metas[1], o1},
		{Min: 21, Max: 30}: {metas[2], o2}, {Min: 30, Max: 31}: {o2, metas[3]},
		{Min: 34, Max: 36}: {metas[3], o3a, o3b},
		{Min: 50, Max: 60}: {metas[5], o4},
		{Min: 61, Max: 70}: {metas[6], o5}, {Min: 70, Max: 80}: {o5, metas[7]}, {Min: 80, Max: 85}: {o5, metas[8]},
		{Min: 94, Max: 99}: {metas[9], o6a, o6b}, {Min: 100, Max: 105}: {o6a, metas[10]},
	}, OverlappingBlocks(add(o1, o2, o3a, o3b, o4, o5, o6a, o6b)))

	// Additional case.
	var nc1 []BlockMeta
	nc1 = append(nc1, BlockMeta{MinTime: 1, MaxTime: 5})
	nc1 = append(nc1, BlockMeta{MinTime: 2, MaxTime: 3})
	nc1 = append(nc1, BlockMeta{MinTime: 2, MaxTime: 3})
	nc1 = append(nc1, BlockMeta{MinTime: 2, MaxTime: 3})
	nc1 = append(nc1, BlockMeta{MinTime: 2, MaxTime: 3})
	nc1 = append(nc1, BlockMeta{MinTime: 2, MaxTime: 6})
	nc1 = append(nc1, BlockMeta{MinTime: 3, MaxTime: 5})
	nc1 = append(nc1, BlockMeta{MinTime: 5, MaxTime: 7})
	nc1 = append(nc1, BlockMeta{MinTime: 7, MaxTime: 10})
	nc1 = append(nc1, BlockMeta{MinTime: 8, MaxTime: 9})
	require.Equal(t, Overlaps{
		{Min: 2, Max: 3}: {nc1[0], nc1[1], nc1[2], nc1[3], nc1[4], nc1[5]}, // 1-5, 2-3, 2-3, 2-3, 2-3, 2,6
		{Min: 3, Max: 5}: {nc1[0], nc1[5], nc1[6]},                         // 1-5, 2-6, 3-5
		{Min: 5, Max: 6}: {nc1[5], nc1[7]},                                 // 2-6, 5-7
		{Min: 8, Max: 9}: {nc1[8], nc1[9]},                                 // 7-10, 8-9
	}, OverlappingBlocks(nc1))
}

// Regression test for https://github.com/prometheus/tsdb/issues/347
func TestChunkAtBlockBoundary(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)

	blockRange := db.compactor.(*LeveledCompactor).ranges[0]
	label := labels.FromStrings("foo", "bar")

	for i := int64(0); i < 3; i++ {
		_, err := app.Append(0, label, i*blockRange, 0)
		require.NoError(t, err)
		_, err = app.Append(0, label, i*blockRange+1000, 0)
		require.NoError(t, err)
	}

	err := app.Commit()
	require.NoError(t, err)

	err = db.Compact(ctx)
	require.NoError(t, err)

	var builder labels.ScratchBuilder

	for _, block := range db.Blocks() {
		r, err := block.Index()
		require.NoError(t, err)
		defer r.Close()

		meta := block.Meta()

		k, v := index.AllPostingsKey()
		p, err := r.Postings(ctx, k, v)
		require.NoError(t, err)

		var chks []chunks.Meta

		chunkCount := 0

		for p.Next() {
			err = r.Series(p.At(), &builder, &chks)
			require.NoError(t, err)
			for _, c := range chks {
				require.True(t, meta.MinTime <= c.MinTime && c.MaxTime <= meta.MaxTime,
					"chunk spans beyond block boundaries: [block.MinTime=%d, block.MaxTime=%d]; [chunk.MinTime=%d, chunk.MaxTime=%d]",
					meta.MinTime, meta.MaxTime, c.MinTime, c.MaxTime)
				chunkCount++
			}
		}
		require.Equal(t, 1, chunkCount, "expected 1 chunk in block %s, got %d", meta.ULID, chunkCount)
	}
}

func TestQuerierWithBoundaryChunks(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	ctx := context.Background()
	app := db.Appender(ctx)

	blockRange := db.compactor.(*LeveledCompactor).ranges[0]
	label := labels.FromStrings("foo", "bar")

	for i := int64(0); i < 5; i++ {
		_, err := app.Append(0, label, i*blockRange, 0)
		require.NoError(t, err)
		_, err = app.Append(0, labels.FromStrings("blockID", strconv.FormatInt(i, 10)), i*blockRange, 0)
		require.NoError(t, err)
	}

	err := app.Commit()
	require.NoError(t, err)

	err = db.Compact(ctx)
	require.NoError(t, err)

	require.GreaterOrEqual(t, len(db.blocks), 3, "invalid test, less than three blocks in DB")

	q, err := db.Querier(blockRange, 2*blockRange)
	require.NoError(t, err)
	defer q.Close()

	// The requested interval covers 2 blocks, so the querier's label values for blockID should give us 2 values, one from each block.
	b, ws, err := q.LabelValues(ctx, "blockID")
	require.NoError(t, err)
	var nilAnnotations annotations.Annotations
	require.Equal(t, nilAnnotations, ws)
	require.Equal(t, []string{"1", "2"}, b)
}

// TestInitializeHeadTimestamp ensures that the h.minTime is set properly.
//   - no blocks no WAL: set to the time of the first  appended sample
//   - no blocks with WAL: set to the smallest sample from the WAL
//   - with blocks no WAL: set to the last block maxT
//   - with blocks with WAL: same as above
func TestInitializeHeadTimestamp(t *testing.T) {
	t.Run("clean", func(t *testing.T) {
		dir := t.TempDir()

		db, err := Open(dir, nil, nil, nil, nil)
		require.NoError(t, err)
		defer db.Close()

		// Should be set to init values if no WAL or blocks exist so far.
		require.Equal(t, int64(math.MaxInt64), db.head.MinTime())
		require.Equal(t, int64(math.MinInt64), db.head.MaxTime())

		// First added sample initializes the writable range.
		ctx := context.Background()
		app := db.Appender(ctx)
		_, err = app.Append(0, labels.FromStrings("a", "b"), 1000, 1)
		require.NoError(t, err)

		require.Equal(t, int64(1000), db.head.MinTime())
		require.Equal(t, int64(1000), db.head.MaxTime())
	})
	t.Run("wal-only", func(t *testing.T) {
		dir := t.TempDir()

		require.NoError(t, os.MkdirAll(path.Join(dir, "wal"), 0o777))
		w, err := wlog.New(nil, nil, path.Join(dir, "wal"), wlog.CompressionNone)
		require.NoError(t, err)

		var enc record.Encoder
		err = w.Log(
			enc.Series([]record.RefSeries{
				{Ref: 123, Labels: labels.FromStrings("a", "1")},
				{Ref: 124, Labels: labels.FromStrings("a", "2")},
			}, nil),
			enc.Samples([]record.RefSample{
				{Ref: 123, T: 5000, V: 1},
				{Ref: 124, T: 15000, V: 1},
			}, nil),
		)
		require.NoError(t, err)
		require.NoError(t, w.Close())

		db, err := Open(dir, nil, nil, nil, nil)
		require.NoError(t, err)
		defer db.Close()

		require.Equal(t, int64(5000), db.head.MinTime())
		require.Equal(t, int64(15000), db.head.MaxTime())
	})
	t.Run("existing-block", func(t *testing.T) {
		dir := t.TempDir()

		createBlock(t, dir, genSeries(1, 1, 1000, 2000))

		db, err := Open(dir, nil, nil, nil, nil)
		require.NoError(t, err)
		defer db.Close()

		require.Equal(t, int64(2000), db.head.MinTime())
		require.Equal(t, int64(2000), db.head.MaxTime())
	})
	t.Run("existing-block-and-wal", func(t *testing.T) {
		dir := t.TempDir()

		createBlock(t, dir, genSeries(1, 1, 1000, 6000))

		require.NoError(t, os.MkdirAll(path.Join(dir, "wal"), 0o777))
		w, err := wlog.New(nil, nil, path.Join(dir, "wal"), wlog.CompressionNone)
		require.NoError(t, err)

		var enc record.Encoder
		err = w.Log(
			enc.Series([]record.RefSeries{
				{Ref: 123, Labels: labels.FromStrings("a", "1")},
				{Ref: 124, Labels: labels.FromStrings("a", "2")},
			}, nil),
			enc.Samples([]record.RefSample{
				{Ref: 123, T: 5000, V: 1},
				{Ref: 124, T: 15000, V: 1},
			}, nil),
		)
		require.NoError(t, err)
		require.NoError(t, w.Close())

		r := prometheus.NewRegistry()

		db, err := Open(dir, nil, r, nil, nil)
		require.NoError(t, err)
		defer db.Close()

		require.Equal(t, int64(6000), db.head.MinTime())
		require.Equal(t, int64(15000), db.head.MaxTime())
		// Check that old series has been GCed.
		require.Equal(t, 1.0, prom_testutil.ToFloat64(db.head.metrics.series))
	})
}

func TestNoEmptyBlocks(t *testing.T) {
	db := openTestDB(t, nil, []int64{100})
	ctx := context.Background()
	defer func() {
		require.NoError(t, db.Close())
	}()
	db.DisableCompactions()

	rangeToTriggerCompaction := db.compactor.(*LeveledCompactor).ranges[0]/2*3 - 1
	defaultLabel := labels.FromStrings("foo", "bar")
	defaultMatcher := labels.MustNewMatcher(labels.MatchRegexp, "", ".*")

	t.Run("Test no blocks after compact with empty head.", func(t *testing.T) {
		require.NoError(t, db.Compact(ctx))
		actBlocks, err := blockDirs(db.Dir())
		require.NoError(t, err)
		require.Equal(t, len(db.Blocks()), len(actBlocks))
		require.Empty(t, actBlocks)
		require.Equal(t, 0, int(prom_testutil.ToFloat64(db.compactor.(*LeveledCompactor).metrics.Ran)), "no compaction should be triggered here")
	})

	t.Run("Test no blocks after deleting all samples from head.", func(t *testing.T) {
		app := db.Appender(ctx)
		_, err := app.Append(0, defaultLabel, 1, 0)
		require.NoError(t, err)
		_, err = app.Append(0, defaultLabel, 2, 0)
		require.NoError(t, err)
		_, err = app.Append(0, defaultLabel, 3+rangeToTriggerCompaction, 0)
		require.NoError(t, err)
		require.NoError(t, app.Commit())
		require.NoError(t, db.Delete(ctx, math.MinInt64, math.MaxInt64, defaultMatcher))
		require.NoError(t, db.Compact(ctx))
		require.Equal(t, 1, int(prom_testutil.ToFloat64(db.compactor.(*LeveledCompactor).metrics.Ran)), "compaction should have been triggered here")

		actBlocks, err := blockDirs(db.Dir())
		require.NoError(t, err)
		require.Equal(t, len(db.Blocks()), len(actBlocks))
		require.Empty(t, actBlocks)

		app = db.Appender(ctx)
		_, err = app.Append(0, defaultLabel, 1, 0)
		require.Equal(t, storage.ErrOutOfBounds, err, "the head should be truncated so no samples in the past should be allowed")

		// Adding new blocks.
		currentTime := db.Head().MaxTime()
		_, err = app.Append(0, defaultLabel, currentTime, 0)
		require.NoError(t, err)
		_, err = app.Append(0, defaultLabel, currentTime+1, 0)
		require.NoError(t, err)
		_, err = app.Append(0, defaultLabel, currentTime+rangeToTriggerCompaction, 0)
		require.NoError(t, err)
		require.NoError(t, app.Commit())

		require.NoError(t, db.Compact(ctx))
		require.Equal(t, 2, int(prom_testutil.ToFloat64(db.compactor.(*LeveledCompactor).metrics.Ran)), "compaction should have been triggered here")
		actBlocks, err = blockDirs(db.Dir())
		require.NoError(t, err)
		require.Equal(t, len(db.Blocks()), len(actBlocks))
		require.Len(t, actBlocks, 1, "No blocks created when compacting with >0 samples")
	})

	t.Run(`When no new block is created from head, and there are some blocks on disk
	compaction should not run into infinite loop (was seen during development).`, func(t *testing.T) {
		oldBlocks := db.Blocks()
		app := db.Appender(ctx)
		currentTime := db.Head().MaxTime()
		_, err := app.Append(0, defaultLabel, currentTime, 0)
		require.NoError(t, err)
		_, err = app.Append(0, defaultLabel, currentTime+1, 0)
		require.NoError(t, err)
		_, err = app.Append(0, defaultLabel, currentTime+rangeToTriggerCompaction, 0)
		require.NoError(t, err)
		require.NoError(t, app.Commit())
		require.NoError(t, db.head.Delete(ctx, math.MinInt64, math.MaxInt64, defaultMatcher))
		require.NoError(t, db.Compact(ctx))
		require.Equal(t, 3, int(prom_testutil.ToFloat64(db.compactor.(*LeveledCompactor).metrics.Ran)), "compaction should have been triggered here")
		require.Equal(t, oldBlocks, db.Blocks())
	})

	t.Run("Test no blocks remaining after deleting all samples from disk.", func(t *testing.T) {
		currentTime := db.Head().MaxTime()
		blocks := []*BlockMeta{
			{MinTime: currentTime, MaxTime: currentTime + db.compactor.(*LeveledCompactor).ranges[0]},
			{MinTime: currentTime + 100, MaxTime: currentTime + 100 + db.compactor.(*LeveledCompactor).ranges[0]},
		}
		for _, m := range blocks {
			createBlock(t, db.Dir(), genSeries(2, 2, m.MinTime, m.MaxTime))
		}

		oldBlocks := db.Blocks()
		require.NoError(t, db.reloadBlocks())                   // Reload the db to register the new blocks.
		require.Len(t, db.Blocks(), len(blocks)+len(oldBlocks)) // Ensure all blocks are registered.
		require.NoError(t, db.Delete(ctx, math.MinInt64, math.MaxInt64, defaultMatcher))
		require.NoError(t, db.Compact(ctx))
		require.Equal(t, 5, int(prom_testutil.ToFloat64(db.compactor.(*LeveledCompactor).metrics.Ran)), "compaction should have been triggered here once for each block that have tombstones")

		actBlocks, err := blockDirs(db.Dir())
		require.NoError(t, err)
		require.Equal(t, len(db.Blocks()), len(actBlocks))
		require.Len(t, actBlocks, 1, "All samples are deleted. Only the most recent block should remain after compaction.")
	})
}

func TestDB_LabelNames(t *testing.T) {
	ctx := context.Background()
	tests := []struct {
		// Add 'sampleLabels1' -> Test Head -> Compact -> Test Disk ->
		// -> Add 'sampleLabels2' -> Test Head+Disk

		sampleLabels1 [][2]string // For checking head and disk separately.
		// To test Head+Disk, sampleLabels2 should have
		// at least 1 unique label name which is not in sampleLabels1.
		sampleLabels2 [][2]string // // For checking head and disk together.
		exp1          []string    // after adding sampleLabels1.
		exp2          []string    // after adding sampleLabels1 and sampleLabels2.
	}{
		{
			sampleLabels1: [][2]string{
				{"name1", "1"},
				{"name3", "3"},
				{"name2", "2"},
			},
			sampleLabels2: [][2]string{
				{"name4", "4"},
				{"name1", "1"},
			},
			exp1: []string{"name1", "name2", "name3"},
			exp2: []string{"name1", "name2", "name3", "name4"},
		},
		{
			sampleLabels1: [][2]string{
				{"name2", "2"},
				{"name1", "1"},
				{"name2", "2"},
			},
			sampleLabels2: [][2]string{
				{"name6", "6"},
				{"name0", "0"},
			},
			exp1: []string{"name1", "name2"},
			exp2: []string{"name0", "name1", "name2", "name6"},
		},
	}

	blockRange := int64(1000)
	// Appends samples into the database.
	appendSamples := func(db *DB, mint, maxt int64, sampleLabels [][2]string) {
		t.Helper()
		app := db.Appender(ctx)
		for i := mint; i <= maxt; i++ {
			for _, tuple := range sampleLabels {
				label := labels.FromStrings(tuple[0], tuple[1])
				_, err := app.Append(0, label, i*blockRange, 0)
				require.NoError(t, err)
			}
		}
		err := app.Commit()
		require.NoError(t, err)
	}
	for _, tst := range tests {
		ctx := context.Background()
		db := openTestDB(t, nil, nil)
		defer func() {
			require.NoError(t, db.Close())
		}()

		appendSamples(db, 0, 4, tst.sampleLabels1)

		// Testing head.
		headIndexr, err := db.head.Index()
		require.NoError(t, err)
		labelNames, err := headIndexr.LabelNames(ctx)
		require.NoError(t, err)
		require.Equal(t, tst.exp1, labelNames)
		require.NoError(t, headIndexr.Close())

		// Testing disk.
		err = db.Compact(ctx)
		require.NoError(t, err)
		// All blocks have same label names, hence check them individually.
		// No need to aggregate and check.
		for _, b := range db.Blocks() {
			blockIndexr, err := b.Index()
			require.NoError(t, err)
			labelNames, err = blockIndexr.LabelNames(ctx)
			require.NoError(t, err)
			require.Equal(t, tst.exp1, labelNames)
			require.NoError(t, blockIndexr.Close())
		}

		// Adding more samples to head with new label names
		// so that we can test (head+disk).LabelNames(ctx) (the union).
		appendSamples(db, 5, 9, tst.sampleLabels2)

		// Testing DB (union).
		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		var ws annotations.Annotations
		labelNames, ws, err = q.LabelNames(ctx)
		require.NoError(t, err)
		require.Empty(t, ws)
		require.NoError(t, q.Close())
		require.Equal(t, tst.exp2, labelNames)
	}
}

func TestCorrectNumTombstones(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	blockRange := db.compactor.(*LeveledCompactor).ranges[0]
	name, value := "foo", "bar"
	defaultLabel := labels.FromStrings(name, value)
	defaultMatcher := labels.MustNewMatcher(labels.MatchEqual, name, value)

	ctx := context.Background()
	app := db.Appender(ctx)
	for i := int64(0); i < 3; i++ {
		for j := int64(0); j < 15; j++ {
			_, err := app.Append(0, defaultLabel, i*blockRange+j, 0)
			require.NoError(t, err)
		}
	}
	require.NoError(t, app.Commit())

	err := db.Compact(ctx)
	require.NoError(t, err)
	require.Len(t, db.blocks, 1)

	require.NoError(t, db.Delete(ctx, 0, 1, defaultMatcher))
	require.Equal(t, uint64(1), db.blocks[0].meta.Stats.NumTombstones)

	// {0, 1} and {2, 3} are merged to form 1 tombstone.
	require.NoError(t, db.Delete(ctx, 2, 3, defaultMatcher))
	require.Equal(t, uint64(1), db.blocks[0].meta.Stats.NumTombstones)

	require.NoError(t, db.Delete(ctx, 5, 6, defaultMatcher))
	require.Equal(t, uint64(2), db.blocks[0].meta.Stats.NumTombstones)

	require.NoError(t, db.Delete(ctx, 9, 11, defaultMatcher))
	require.Equal(t, uint64(3), db.blocks[0].meta.Stats.NumTombstones)
}

// TestBlockRanges checks the following use cases:
//   - No samples can be added with timestamps lower than the last block maxt.
//   - The compactor doesn't create overlapping blocks
//
// even when the last blocks is not within the default boundaries.
//   - Lower boundary is based on the smallest sample in the head and
//
// upper boundary is rounded to the configured block range.
//
// This ensures that a snapshot that includes the head and creates a block with a custom time range
// will not overlap with the first block created by the next compaction.
func TestBlockRanges(t *testing.T) {
	logger := log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
	ctx := context.Background()

	dir := t.TempDir()

	// Test that the compactor doesn't create overlapping blocks
	// when a non standard block already exists.
	firstBlockMaxT := int64(3)
	createBlock(t, dir, genSeries(1, 1, 0, firstBlockMaxT))
	db, err := open(dir, logger, nil, DefaultOptions(), []int64{10000}, nil)
	require.NoError(t, err)

	rangeToTriggerCompaction := db.compactor.(*LeveledCompactor).ranges[0]/2*3 + 1

	app := db.Appender(ctx)
	lbl := labels.FromStrings("a", "b")
	_, err = app.Append(0, lbl, firstBlockMaxT-1, rand.Float64())
	require.Error(t, err, "appending a sample with a timestamp covered by a previous block shouldn't be possible")
	_, err = app.Append(0, lbl, firstBlockMaxT+1, rand.Float64())
	require.NoError(t, err)
	_, err = app.Append(0, lbl, firstBlockMaxT+2, rand.Float64())
	require.NoError(t, err)
	secondBlockMaxt := firstBlockMaxT + rangeToTriggerCompaction
	_, err = app.Append(0, lbl, secondBlockMaxt, rand.Float64()) // Add samples to trigger a new compaction

	require.NoError(t, err)
	require.NoError(t, app.Commit())
	for x := 0; x < 100; x++ {
		if len(db.Blocks()) == 2 {
			break
		}
		time.Sleep(100 * time.Millisecond)
	}
	require.Len(t, db.Blocks(), 2, "no new block created after the set timeout")

	require.LessOrEqual(t, db.Blocks()[1].Meta().MinTime, db.Blocks()[0].Meta().MaxTime,
		"new block overlaps  old:%v,new:%v", db.Blocks()[0].Meta(), db.Blocks()[1].Meta())

	// Test that wal records are skipped when an existing block covers the same time ranges
	// and compaction doesn't create an overlapping block.
	app = db.Appender(ctx)
	db.DisableCompactions()
	_, err = app.Append(0, lbl, secondBlockMaxt+1, rand.Float64())
	require.NoError(t, err)
	_, err = app.Append(0, lbl, secondBlockMaxt+2, rand.Float64())
	require.NoError(t, err)
	_, err = app.Append(0, lbl, secondBlockMaxt+3, rand.Float64())
	require.NoError(t, err)
	_, err = app.Append(0, lbl, secondBlockMaxt+4, rand.Float64())
	require.NoError(t, err)
	require.NoError(t, app.Commit())
	require.NoError(t, db.Close())

	thirdBlockMaxt := secondBlockMaxt + 2
	createBlock(t, dir, genSeries(1, 1, secondBlockMaxt+1, thirdBlockMaxt))

	db, err = open(dir, logger, nil, DefaultOptions(), []int64{10000}, nil)
	require.NoError(t, err)

	defer db.Close()
	require.Len(t, db.Blocks(), 3, "db doesn't include expected number of blocks")
	require.Equal(t, db.Blocks()[2].Meta().MaxTime, thirdBlockMaxt, "unexpected maxt of the last block")

	app = db.Appender(ctx)
	_, err = app.Append(0, lbl, thirdBlockMaxt+rangeToTriggerCompaction, rand.Float64()) // Trigger a compaction
	require.NoError(t, err)
	require.NoError(t, app.Commit())
	for x := 0; x < 100; x++ {
		if len(db.Blocks()) == 4 {
			break
		}
		time.Sleep(100 * time.Millisecond)
	}

	require.Len(t, db.Blocks(), 4, "no new block created after the set timeout")

	require.LessOrEqual(t, db.Blocks()[3].Meta().MinTime, db.Blocks()[2].Meta().MaxTime,
		"new block overlaps  old:%v,new:%v", db.Blocks()[2].Meta(), db.Blocks()[3].Meta())
}

// TestDBReadOnly ensures that opening a DB in readonly mode doesn't modify any files on the disk.
// It also checks that the API calls return equivalent results as a normal db.Open() mode.
func TestDBReadOnly(t *testing.T) {
	var (
		dbDir     string
		logger    = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
		expBlocks []*Block
		expBlock  *Block
		expSeries map[string][]chunks.Sample
		expChunks map[string][][]chunks.Sample
		expDBHash []byte
		matchAll  = labels.MustNewMatcher(labels.MatchEqual, "", "")
		err       error
	)

	// Bootstrap the db.
	{
		dbDir = t.TempDir()

		dbBlocks := []*BlockMeta{
			// Create three 2-sample blocks.
			{MinTime: 10, MaxTime: 12},
			{MinTime: 12, MaxTime: 14},
			{MinTime: 14, MaxTime: 16},
		}

		for _, m := range dbBlocks {
			_ = createBlock(t, dbDir, genSeries(1, 1, m.MinTime, m.MaxTime))
		}

		// Add head to test DBReadOnly WAL reading capabilities.
		w, err := wlog.New(logger, nil, filepath.Join(dbDir, "wal"), wlog.CompressionSnappy)
		require.NoError(t, err)
		h := createHead(t, w, genSeries(1, 1, 16, 18), dbDir)
		require.NoError(t, h.Close())
	}

	// Open a normal db to use for a comparison.
	{
		dbWritable, err := Open(dbDir, logger, nil, nil, nil)
		require.NoError(t, err)
		dbWritable.DisableCompactions()

		dbSizeBeforeAppend, err := fileutil.DirSize(dbWritable.Dir())
		require.NoError(t, err)
		app := dbWritable.Appender(context.Background())
		_, err = app.Append(0, labels.FromStrings("foo", "bar"), dbWritable.Head().MaxTime()+1, 0)
		require.NoError(t, err)
		require.NoError(t, app.Commit())

		expBlocks = dbWritable.Blocks()
		expBlock = expBlocks[0]
		expDbSize, err := fileutil.DirSize(dbWritable.Dir())
		require.NoError(t, err)
		require.Greater(t, expDbSize, dbSizeBeforeAppend, "db size didn't increase after an append")

		q, err := dbWritable.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		expSeries = query(t, q, matchAll)
		cq, err := dbWritable.ChunkQuerier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		expChunks = queryAndExpandChunks(t, cq, matchAll)

		require.NoError(t, dbWritable.Close()) // Close here to allow getting the dir hash for windows.
		expDBHash = testutil.DirHash(t, dbWritable.Dir())
	}

	// Open a read only db and ensure that the API returns the same result as the normal DB.
	dbReadOnly, err := OpenDBReadOnly(dbDir, logger)
	require.NoError(t, err)
	defer func() { require.NoError(t, dbReadOnly.Close()) }()

	t.Run("blocks", func(t *testing.T) {
		blocks, err := dbReadOnly.Blocks()
		require.NoError(t, err)
		require.Equal(t, len(expBlocks), len(blocks))
		for i, expBlock := range expBlocks {
			require.Equal(t, expBlock.Meta(), blocks[i].Meta(), "block meta mismatch")
		}
	})
	t.Run("block", func(t *testing.T) {
		blockID := expBlock.meta.ULID.String()
		block, err := dbReadOnly.Block(blockID)
		require.NoError(t, err)
		require.Equal(t, expBlock.Meta(), block.Meta(), "block meta mismatch")
	})
	t.Run("invalid block ID", func(t *testing.T) {
		blockID := "01GTDVZZF52NSWB5SXQF0P2PGF"
		_, err := dbReadOnly.Block(blockID)
		require.Error(t, err)
	})
	t.Run("last block ID", func(t *testing.T) {
		blockID, err := dbReadOnly.LastBlockID()
		require.NoError(t, err)
		require.Equal(t, expBlocks[2].Meta().ULID.String(), blockID)
	})
	t.Run("querier", func(t *testing.T) {
		// Open a read only db and ensure that the API returns the same result as the normal DB.
		q, err := dbReadOnly.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		readOnlySeries := query(t, q, matchAll)
		readOnlyDBHash := testutil.DirHash(t, dbDir)

		require.Equal(t, len(expSeries), len(readOnlySeries), "total series mismatch")
		require.Equal(t, expSeries, readOnlySeries, "series mismatch")
		require.Equal(t, expDBHash, readOnlyDBHash, "after all read operations the db hash should remain the same")
	})
	t.Run("chunk querier", func(t *testing.T) {
		cq, err := dbReadOnly.ChunkQuerier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		readOnlySeries := queryAndExpandChunks(t, cq, matchAll)
		readOnlyDBHash := testutil.DirHash(t, dbDir)

		require.Equal(t, len(expChunks), len(readOnlySeries), "total series mismatch")
		require.Equal(t, expChunks, readOnlySeries, "series chunks mismatch")
		require.Equal(t, expDBHash, readOnlyDBHash, "after all read operations the db hash should remain the same")
	})
}

// TestDBReadOnlyClosing ensures that after closing the db
// all api methods return an ErrClosed.
func TestDBReadOnlyClosing(t *testing.T) {
	dbDir := t.TempDir()
	db, err := OpenDBReadOnly(dbDir, log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr)))
	require.NoError(t, err)
	require.NoError(t, db.Close())
	require.Equal(t, db.Close(), ErrClosed)
	_, err = db.Blocks()
	require.Equal(t, err, ErrClosed)
	_, err = db.Querier(0, 1)
	require.Equal(t, err, ErrClosed)
}

func TestDBReadOnly_FlushWAL(t *testing.T) {
	var (
		dbDir  string
		logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
		err    error
		maxt   int
		ctx    = context.Background()
	)

	// Bootstrap the db.
	{
		dbDir = t.TempDir()

		// Append data to the WAL.
		db, err := Open(dbDir, logger, nil, nil, nil)
		require.NoError(t, err)
		db.DisableCompactions()
		app := db.Appender(ctx)
		maxt = 1000
		for i := 0; i < maxt; i++ {
			_, err := app.Append(0, labels.FromStrings(defaultLabelName, "flush"), int64(i), 1.0)
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
		require.NoError(t, db.Close())
	}

	// Flush WAL.
	db, err := OpenDBReadOnly(dbDir, logger)
	require.NoError(t, err)

	flush := t.TempDir()
	require.NoError(t, db.FlushWAL(flush))
	require.NoError(t, db.Close())

	// Reopen the DB from the flushed WAL block.
	db, err = OpenDBReadOnly(flush, logger)
	require.NoError(t, err)
	defer func() { require.NoError(t, db.Close()) }()
	blocks, err := db.Blocks()
	require.NoError(t, err)
	require.Len(t, blocks, 1)

	querier, err := db.Querier(0, int64(maxt)-1)
	require.NoError(t, err)
	defer func() { require.NoError(t, querier.Close()) }()

	// Sum the values.
	seriesSet := querier.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, defaultLabelName, "flush"))
	var series chunkenc.Iterator

	sum := 0.0
	for seriesSet.Next() {
		series = seriesSet.At().Iterator(series)
		for series.Next() == chunkenc.ValFloat {
			_, v := series.At()
			sum += v
		}
		require.NoError(t, series.Err())
	}
	require.NoError(t, seriesSet.Err())
	require.Empty(t, seriesSet.Warnings())
	require.Equal(t, 1000.0, sum)
}

func TestDBCannotSeePartialCommits(t *testing.T) {
	if defaultIsolationDisabled {
		t.Skip("skipping test since tsdb isolation is disabled")
	}

	tmpdir := t.TempDir()

	db, err := Open(tmpdir, nil, nil, nil, nil)
	require.NoError(t, err)
	defer db.Close()

	stop := make(chan struct{})
	firstInsert := make(chan struct{})
	ctx := context.Background()

	// Insert data in batches.
	go func() {
		iter := 0
		for {
			app := db.Appender(ctx)

			for j := 0; j < 100; j++ {
				_, err := app.Append(0, labels.FromStrings("foo", "bar", "a", strconv.Itoa(j)), int64(iter), float64(iter))
				require.NoError(t, err)
			}
			err = app.Commit()
			require.NoError(t, err)

			if iter == 0 {
				close(firstInsert)
			}
			iter++

			select {
			case <-stop:
				return
			default:
			}
		}
	}()

	<-firstInsert

	// This is a race condition, so do a few tests to tickle it.
	// Usually most will fail.
	inconsistencies := 0
	for i := 0; i < 10; i++ {
		func() {
			querier, err := db.Querier(0, 1000000)
			require.NoError(t, err)
			defer querier.Close()

			ss := querier.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
			_, seriesSet, ws, err := expandSeriesSet(ss)
			require.NoError(t, err)
			require.Empty(t, ws)

			values := map[float64]struct{}{}
			for _, series := range seriesSet {
				values[series[len(series)-1].f] = struct{}{}
			}
			if len(values) != 1 {
				inconsistencies++
			}
		}()
	}
	stop <- struct{}{}

	require.Equal(t, 0, inconsistencies, "Some queries saw inconsistent results.")
}

func TestDBQueryDoesntSeeAppendsAfterCreation(t *testing.T) {
	if defaultIsolationDisabled {
		t.Skip("skipping test since tsdb isolation is disabled")
	}

	tmpdir := t.TempDir()

	db, err := Open(tmpdir, nil, nil, nil, nil)
	require.NoError(t, err)
	defer db.Close()

	querierBeforeAdd, err := db.Querier(0, 1000000)
	require.NoError(t, err)
	defer querierBeforeAdd.Close()

	ctx := context.Background()
	app := db.Appender(ctx)
	_, err = app.Append(0, labels.FromStrings("foo", "bar"), 0, 0)
	require.NoError(t, err)

	querierAfterAddButBeforeCommit, err := db.Querier(0, 1000000)
	require.NoError(t, err)
	defer querierAfterAddButBeforeCommit.Close()

	// None of the queriers should return anything after the Add but before the commit.
	ss := querierBeforeAdd.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	_, seriesSet, ws, err := expandSeriesSet(ss)
	require.NoError(t, err)
	require.Empty(t, ws)
	require.Equal(t, map[string][]sample{}, seriesSet)

	ss = querierAfterAddButBeforeCommit.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	_, seriesSet, ws, err = expandSeriesSet(ss)
	require.NoError(t, err)
	require.Empty(t, ws)
	require.Equal(t, map[string][]sample{}, seriesSet)

	// This commit is after the queriers are created, so should not be returned.
	err = app.Commit()
	require.NoError(t, err)

	// Nothing returned for querier created before the Add.
	ss = querierBeforeAdd.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	_, seriesSet, ws, err = expandSeriesSet(ss)
	require.NoError(t, err)
	require.Empty(t, ws)
	require.Equal(t, map[string][]sample{}, seriesSet)

	// Series exists but has no samples for querier created after Add.
	ss = querierAfterAddButBeforeCommit.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	_, seriesSet, ws, err = expandSeriesSet(ss)
	require.NoError(t, err)
	require.Empty(t, ws)
	require.Equal(t, map[string][]sample{`{foo="bar"}`: {}}, seriesSet)

	querierAfterCommit, err := db.Querier(0, 1000000)
	require.NoError(t, err)
	defer querierAfterCommit.Close()

	// Samples are returned for querier created after Commit.
	ss = querierAfterCommit.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	_, seriesSet, ws, err = expandSeriesSet(ss)
	require.NoError(t, err)
	require.Empty(t, ws)
	require.Equal(t, map[string][]sample{`{foo="bar"}`: {{t: 0, f: 0}}}, seriesSet)
}

func assureChunkFromSamples(t *testing.T, samples []chunks.Sample) chunks.Meta {
	chks, err := chunks.ChunkFromSamples(samples)
	require.NoError(t, err)
	return chks
}

// TestChunkWriter_ReadAfterWrite ensures that chunk segment are cut at the set segment size and
// that the resulted segments includes the expected chunks data.
func TestChunkWriter_ReadAfterWrite(t *testing.T) {
	chk1 := assureChunkFromSamples(t, []chunks.Sample{sample{1, 1, nil, nil}})
	chk2 := assureChunkFromSamples(t, []chunks.Sample{sample{1, 2, nil, nil}})
	chk3 := assureChunkFromSamples(t, []chunks.Sample{sample{1, 3, nil, nil}})
	chk4 := assureChunkFromSamples(t, []chunks.Sample{sample{1, 4, nil, nil}})
	chk5 := assureChunkFromSamples(t, []chunks.Sample{sample{1, 5, nil, nil}})
	chunkSize := len(chk1.Chunk.Bytes()) + chunks.MaxChunkLengthFieldSize + chunks.ChunkEncodingSize + crc32.Size

	tests := []struct {
		chks [][]chunks.Meta
		segmentSize,
		expSegmentsCount int
		expSegmentSizes []int
	}{
		// 0:Last chunk ends at the segment boundary so
		// all chunks should fit in a single segment.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
					chk2,
					chk3,
				},
			},
			segmentSize:      3 * chunkSize,
			expSegmentSizes:  []int{3 * chunkSize},
			expSegmentsCount: 1,
		},
		// 1:Two chunks can fit in a single segment so the last one should result in a new segment.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
					chk2,
					chk3,
					chk4,
					chk5,
				},
			},
			segmentSize:      2 * chunkSize,
			expSegmentSizes:  []int{2 * chunkSize, 2 * chunkSize, chunkSize},
			expSegmentsCount: 3,
		},
		// 2:When the segment size is smaller than the size of 2 chunks
		// the last segment should still create a new segment.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
					chk2,
					chk3,
				},
			},
			segmentSize:      2*chunkSize - 1,
			expSegmentSizes:  []int{chunkSize, chunkSize, chunkSize},
			expSegmentsCount: 3,
		},
		// 3:When the segment is smaller than a single chunk
		// it should still be written by ignoring the max segment size.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
				},
			},
			segmentSize:      chunkSize - 1,
			expSegmentSizes:  []int{chunkSize},
			expSegmentsCount: 1,
		},
		// 4:All chunks are bigger than the max segment size, but
		// these should still be written even when this will result in bigger segment than the set size.
		// Each segment will hold a single chunk.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
					chk2,
					chk3,
				},
			},
			segmentSize:      1,
			expSegmentSizes:  []int{chunkSize, chunkSize, chunkSize},
			expSegmentsCount: 3,
		},
		// 5:Adding multiple batches of chunks.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
					chk2,
					chk3,
				},
				{
					chk4,
					chk5,
				},
			},
			segmentSize:      3 * chunkSize,
			expSegmentSizes:  []int{3 * chunkSize, 2 * chunkSize},
			expSegmentsCount: 2,
		},
		// 6:Adding multiple batches of chunks.
		{
			chks: [][]chunks.Meta{
				{
					chk1,
				},
				{
					chk2,
					chk3,
				},
				{
					chk4,
				},
			},
			segmentSize:      2 * chunkSize,
			expSegmentSizes:  []int{2 * chunkSize, 2 * chunkSize},
			expSegmentsCount: 2,
		},
	}

	for i, test := range tests {
		t.Run(strconv.Itoa(i), func(t *testing.T) {
			tempDir := t.TempDir()

			chunkw, err := chunks.NewWriterWithSegSize(tempDir, chunks.SegmentHeaderSize+int64(test.segmentSize))
			require.NoError(t, err)

			for _, chks := range test.chks {
				require.NoError(t, chunkw.WriteChunks(chks...))
			}
			require.NoError(t, chunkw.Close())

			files, err := os.ReadDir(tempDir)
			require.NoError(t, err)
			require.Len(t, files, test.expSegmentsCount, "expected segments count mismatch")

			// Verify that all data is written to the segments.
			sizeExp := 0
			sizeAct := 0

			for _, chks := range test.chks {
				for _, chk := range chks {
					l := make([]byte, binary.MaxVarintLen32)
					sizeExp += binary.PutUvarint(l, uint64(len(chk.Chunk.Bytes()))) // The length field.
					sizeExp += chunks.ChunkEncodingSize
					sizeExp += len(chk.Chunk.Bytes()) // The data itself.
					sizeExp += crc32.Size             // The 4 bytes of crc32
				}
			}
			sizeExp += test.expSegmentsCount * chunks.SegmentHeaderSize // The segment header bytes.

			for i, f := range files {
				fi, err := f.Info()
				require.NoError(t, err)
				size := int(fi.Size())
				// Verify that the segment is the same or smaller than the expected size.
				require.GreaterOrEqual(t, chunks.SegmentHeaderSize+test.expSegmentSizes[i], size, "Segment:%v should NOT be bigger than:%v actual:%v", i, chunks.SegmentHeaderSize+test.expSegmentSizes[i], size)

				sizeAct += size
			}
			require.Equal(t, sizeExp, sizeAct)

			// Check the content of the chunks.
			r, err := chunks.NewDirReader(tempDir, nil)
			require.NoError(t, err)
			defer func() { require.NoError(t, r.Close()) }()

			for _, chks := range test.chks {
				for _, chkExp := range chks {
					chkAct, iterable, err := r.ChunkOrIterable(chkExp)
					require.NoError(t, err)
					require.Nil(t, iterable)
					require.Equal(t, chkExp.Chunk.Bytes(), chkAct.Bytes())
				}
			}
		})
	}
}

func TestRangeForTimestamp(t *testing.T) {
	type args struct {
		t     int64
		width int64
	}
	tests := []struct {
		args     args
		expected int64
	}{
		{args{0, 5}, 5},
		{args{1, 5}, 5},
		{args{5, 5}, 10},
		{args{6, 5}, 10},
		{args{13, 5}, 15},
		{args{95, 5}, 100},
	}
	for _, tt := range tests {
		got := rangeForTimestamp(tt.args.t, tt.args.width)
		require.Equal(t, tt.expected, got)
	}
}

// TestChunkReader_ConcurrentReads checks that the chunk result can be read concurrently.
// Regression test for https://github.com/prometheus/prometheus/pull/6514.
func TestChunkReader_ConcurrentReads(t *testing.T) {
	chks := []chunks.Meta{
		assureChunkFromSamples(t, []chunks.Sample{sample{1, 1, nil, nil}}),
		assureChunkFromSamples(t, []chunks.Sample{sample{1, 2, nil, nil}}),
		assureChunkFromSamples(t, []chunks.Sample{sample{1, 3, nil, nil}}),
		assureChunkFromSamples(t, []chunks.Sample{sample{1, 4, nil, nil}}),
		assureChunkFromSamples(t, []chunks.Sample{sample{1, 5, nil, nil}}),
	}

	tempDir := t.TempDir()

	chunkw, err := chunks.NewWriter(tempDir)
	require.NoError(t, err)

	require.NoError(t, chunkw.WriteChunks(chks...))
	require.NoError(t, chunkw.Close())

	r, err := chunks.NewDirReader(tempDir, nil)
	require.NoError(t, err)

	var wg sync.WaitGroup
	for _, chk := range chks {
		for i := 0; i < 100; i++ {
			wg.Add(1)
			go func(chunk chunks.Meta) {
				defer wg.Done()

				chkAct, iterable, err := r.ChunkOrIterable(chunk)
				require.NoError(t, err)
				require.Nil(t, iterable)
				require.Equal(t, chunk.Chunk.Bytes(), chkAct.Bytes())
			}(chk)
		}
		wg.Wait()
	}
	require.NoError(t, r.Close())
}

// TestCompactHead ensures that the head compaction
// creates a block that is ready for loading and
// does not cause data loss.
// This test:
// * opens a storage;
// * appends values;
// * compacts the head; and
// * queries the db to ensure the samples are present from the compacted head.
func TestCompactHead(t *testing.T) {
	dbDir := t.TempDir()

	// Open a DB and append data to the WAL.
	tsdbCfg := &Options{
		RetentionDuration: int64(time.Hour * 24 * 15 / time.Millisecond),
		NoLockfile:        true,
		MinBlockDuration:  int64(time.Hour * 2 / time.Millisecond),
		MaxBlockDuration:  int64(time.Hour * 2 / time.Millisecond),
		WALCompression:    wlog.CompressionSnappy,
	}

	db, err := Open(dbDir, log.NewNopLogger(), prometheus.NewRegistry(), tsdbCfg, nil)
	require.NoError(t, err)
	ctx := context.Background()
	app := db.Appender(ctx)
	var expSamples []sample
	maxt := 100
	for i := 0; i < maxt; i++ {
		val := rand.Float64()
		_, err := app.Append(0, labels.FromStrings("a", "b"), int64(i), val)
		require.NoError(t, err)
		expSamples = append(expSamples, sample{int64(i), val, nil, nil})
	}
	require.NoError(t, app.Commit())

	// Compact the Head to create a new block.
	require.NoError(t, db.CompactHead(NewRangeHead(db.Head(), 0, int64(maxt)-1)))
	require.NoError(t, db.Close())

	// Delete everything but the new block and
	// reopen the db to query it to ensure it includes the head data.
	require.NoError(t, deleteNonBlocks(db.Dir()))
	db, err = Open(dbDir, log.NewNopLogger(), prometheus.NewRegistry(), tsdbCfg, nil)
	require.NoError(t, err)
	require.Len(t, db.Blocks(), 1)
	require.Equal(t, int64(maxt), db.Head().MinTime())
	defer func() { require.NoError(t, db.Close()) }()
	querier, err := db.Querier(0, int64(maxt)-1)
	require.NoError(t, err)
	defer func() { require.NoError(t, querier.Close()) }()

	seriesSet := querier.Select(ctx, false, nil, &labels.Matcher{Type: labels.MatchEqual, Name: "a", Value: "b"})
	var series chunkenc.Iterator
	var actSamples []sample

	for seriesSet.Next() {
		series = seriesSet.At().Iterator(series)
		for series.Next() == chunkenc.ValFloat {
			time, val := series.At()
			actSamples = append(actSamples, sample{time, val, nil, nil})
		}
		require.NoError(t, series.Err())
	}
	require.Equal(t, expSamples, actSamples)
	require.NoError(t, seriesSet.Err())
}

// TestCompactHeadWithDeletion tests https://github.com/prometheus/prometheus/issues/11585.
func TestCompactHeadWithDeletion(t *testing.T) {
	db, err := Open(t.TempDir(), log.NewNopLogger(), prometheus.NewRegistry(), nil, nil)
	require.NoError(t, err)

	ctx := context.Background()

	app := db.Appender(ctx)
	_, err = app.Append(0, labels.FromStrings("a", "b"), 10, rand.Float64())
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	err = db.Delete(ctx, 0, 100, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))
	require.NoError(t, err)

	// This recreates the bug.
	require.NoError(t, db.CompactHead(NewRangeHead(db.Head(), 0, 100)))
	require.NoError(t, db.Close())
}

func deleteNonBlocks(dbDir string) error {
	dirs, err := os.ReadDir(dbDir)
	if err != nil {
		return err
	}
	for _, dir := range dirs {
		if ok := isBlockDir(dir); !ok {
			if err := os.RemoveAll(filepath.Join(dbDir, dir.Name())); err != nil {
				return err
			}
		}
	}
	dirs, err = os.ReadDir(dbDir)
	if err != nil {
		return err
	}
	for _, dir := range dirs {
		if ok := isBlockDir(dir); !ok {
			return fmt.Errorf("root folder:%v still hase non block directory:%v", dbDir, dir.Name())
		}
	}
	return nil
}

func TestOpen_VariousBlockStates(t *testing.T) {
	tmpDir := t.TempDir()

	var (
		expectedLoadedDirs  = map[string]struct{}{}
		expectedRemovedDirs = map[string]struct{}{}
		expectedIgnoredDirs = map[string]struct{}{}
	)

	{
		// Ok blocks; should be loaded.
		expectedLoadedDirs[createBlock(t, tmpDir, genSeries(10, 2, 0, 10))] = struct{}{}
		expectedLoadedDirs[createBlock(t, tmpDir, genSeries(10, 2, 10, 20))] = struct{}{}
	}
	{
		// Block to repair; should be repaired & loaded.
		dbDir := filepath.Join("testdata", "repair_index_version", "01BZJ9WJQPWHGNC2W4J9TA62KC")
		outDir := filepath.Join(tmpDir, "01BZJ9WJQPWHGNC2W4J9TA62KC")
		expectedLoadedDirs[outDir] = struct{}{}

		// Touch chunks dir in block.
		require.NoError(t, os.MkdirAll(filepath.Join(dbDir, "chunks"), 0o777))
		defer func() {
			require.NoError(t, os.RemoveAll(filepath.Join(dbDir, "chunks")))
		}()
		require.NoError(t, os.Mkdir(outDir, os.ModePerm))
		require.NoError(t, fileutil.CopyDirs(dbDir, outDir))
	}
	{
		// Missing meta.json; should be ignored and only logged.
		// TODO(bwplotka): Probably add metric.
		dir := createBlock(t, tmpDir, genSeries(10, 2, 20, 30))
		expectedIgnoredDirs[dir] = struct{}{}
		require.NoError(t, os.Remove(filepath.Join(dir, metaFilename)))
	}
	{
		// Tmp blocks during creation; those should be removed on start.
		dir := createBlock(t, tmpDir, genSeries(10, 2, 30, 40))
		require.NoError(t, fileutil.Replace(dir, dir+tmpForCreationBlockDirSuffix))
		expectedRemovedDirs[dir+tmpForCreationBlockDirSuffix] = struct{}{}

		// Tmp blocks during deletion; those should be removed on start.
		dir = createBlock(t, tmpDir, genSeries(10, 2, 40, 50))
		require.NoError(t, fileutil.Replace(dir, dir+tmpForDeletionBlockDirSuffix))
		expectedRemovedDirs[dir+tmpForDeletionBlockDirSuffix] = struct{}{}

		// Pre-2.21 tmp blocks; those should be removed on start.
		dir = createBlock(t, tmpDir, genSeries(10, 2, 50, 60))
		require.NoError(t, fileutil.Replace(dir, dir+tmpLegacy))
		expectedRemovedDirs[dir+tmpLegacy] = struct{}{}
	}
	{
		// One ok block; but two should be replaced.
		dir := createBlock(t, tmpDir, genSeries(10, 2, 50, 60))
		expectedLoadedDirs[dir] = struct{}{}

		m, _, err := readMetaFile(dir)
		require.NoError(t, err)

		compacted := createBlock(t, tmpDir, genSeries(10, 2, 50, 55))
		expectedRemovedDirs[compacted] = struct{}{}

		m.Compaction.Parents = append(m.Compaction.Parents,
			BlockDesc{ULID: ulid.MustParse(filepath.Base(compacted))},
			BlockDesc{ULID: ulid.MustNew(1, nil)},
			BlockDesc{ULID: ulid.MustNew(123, nil)},
		)

		// Regression test: Already removed parent can be still in list, which was causing Open errors.
		m.Compaction.Parents = append(m.Compaction.Parents, BlockDesc{ULID: ulid.MustParse(filepath.Base(compacted))})
		m.Compaction.Parents = append(m.Compaction.Parents, BlockDesc{ULID: ulid.MustParse(filepath.Base(compacted))})
		_, err = writeMetaFile(log.NewLogfmtLogger(os.Stderr), dir, m)
		require.NoError(t, err)
	}
	tmpCheckpointDir := path.Join(tmpDir, "wal/checkpoint.00000001.tmp")
	err := os.MkdirAll(tmpCheckpointDir, 0o777)
	require.NoError(t, err)
	tmpChunkSnapshotDir := path.Join(tmpDir, chunkSnapshotPrefix+"0000.00000001.tmp")
	err = os.MkdirAll(tmpChunkSnapshotDir, 0o777)
	require.NoError(t, err)

	opts := DefaultOptions()
	opts.RetentionDuration = 0
	db, err := Open(tmpDir, log.NewLogfmtLogger(os.Stderr), nil, opts, nil)
	require.NoError(t, err)

	loadedBlocks := db.Blocks()

	var loaded int
	for _, l := range loadedBlocks {
		_, ok := expectedLoadedDirs[filepath.Join(tmpDir, l.meta.ULID.String())]
		require.True(t, ok, "unexpected block", l.meta.ULID, "was loaded")
		loaded++
	}
	require.Len(t, expectedLoadedDirs, loaded)
	require.NoError(t, db.Close())

	files, err := os.ReadDir(tmpDir)
	require.NoError(t, err)

	var ignored int
	for _, f := range files {
		_, ok := expectedRemovedDirs[filepath.Join(tmpDir, f.Name())]
		require.False(t, ok, "expected", filepath.Join(tmpDir, f.Name()), "to be removed, but still exists")
		if _, ok := expectedIgnoredDirs[filepath.Join(tmpDir, f.Name())]; ok {
			ignored++
		}
	}
	require.Len(t, expectedIgnoredDirs, ignored)
	_, err = os.Stat(tmpCheckpointDir)
	require.True(t, os.IsNotExist(err))
	_, err = os.Stat(tmpChunkSnapshotDir)
	require.True(t, os.IsNotExist(err))
}

func TestOneCheckpointPerCompactCall(t *testing.T) {
	blockRange := int64(1000)
	tsdbCfg := &Options{
		RetentionDuration: blockRange * 1000,
		NoLockfile:        true,
		MinBlockDuration:  blockRange,
		MaxBlockDuration:  blockRange,
	}

	tmpDir := t.TempDir()
	ctx := context.Background()

	db, err := Open(tmpDir, log.NewNopLogger(), prometheus.NewRegistry(), tsdbCfg, nil)
	require.NoError(t, err)
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})
	db.DisableCompactions()

	// Case 1: Lot's of uncompacted data in Head.

	lbls := labels.FromStrings("foo_d", "choco_bar")
	// Append samples spanning 59 block ranges.
	app := db.Appender(context.Background())
	for i := int64(0); i < 60; i++ {
		_, err := app.Append(0, lbls, blockRange*i, rand.Float64())
		require.NoError(t, err)
		_, err = app.Append(0, lbls, (blockRange*i)+blockRange/2, rand.Float64())
		require.NoError(t, err)
		// Rotate the WAL file so that there is >3 files for checkpoint to happen.
		_, err = db.head.wal.NextSegment()
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	// Check the existing WAL files.
	first, last, err := wlog.Segments(db.head.wal.Dir())
	require.NoError(t, err)
	require.Equal(t, 0, first)
	require.Equal(t, 60, last)

	require.Equal(t, 0.0, prom_testutil.ToFloat64(db.head.metrics.checkpointCreationTotal))
	require.NoError(t, db.Compact(ctx))
	require.Equal(t, 1.0, prom_testutil.ToFloat64(db.head.metrics.checkpointCreationTotal))

	// As the data spans for 59 blocks, 58 go to disk and 1 remains in Head.
	require.Len(t, db.Blocks(), 58)
	// Though WAL was truncated only once, head should be truncated after each compaction.
	require.Equal(t, 58.0, prom_testutil.ToFloat64(db.head.metrics.headTruncateTotal))

	// The compaction should have only truncated first 2/3 of WAL (while also rotating the files).
	first, last, err = wlog.Segments(db.head.wal.Dir())
	require.NoError(t, err)
	require.Equal(t, 40, first)
	require.Equal(t, 61, last)

	// The first checkpoint would be for first 2/3rd of WAL, hence till 39.
	// That should be the last checkpoint.
	_, cno, err := wlog.LastCheckpoint(db.head.wal.Dir())
	require.NoError(t, err)
	require.Equal(t, 39, cno)

	// Case 2: Old blocks on disk.
	// The above blocks will act as old blocks.

	// Creating a block to cover the data in the Head so that
	// Head will skip the data during replay and start fresh.
	blocks := db.Blocks()
	newBlockMint := blocks[len(blocks)-1].Meta().MaxTime
	newBlockMaxt := db.Head().MaxTime() + 1
	require.NoError(t, db.Close())

	createBlock(t, db.dir, genSeries(1, 1, newBlockMint, newBlockMaxt))

	db, err = Open(db.dir, log.NewNopLogger(), prometheus.NewRegistry(), tsdbCfg, nil)
	require.NoError(t, err)
	db.DisableCompactions()

	// 1 block more.
	require.Len(t, db.Blocks(), 59)
	// No series in Head because of this new block.
	require.Equal(t, 0, int(db.head.NumSeries()))

	// Adding sample way into the future.
	app = db.Appender(context.Background())
	_, err = app.Append(0, lbls, blockRange*120, rand.Float64())
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	// The mint of head is the last block maxt, that means the gap between mint and maxt
	// of Head is too large. This will trigger many compactions.
	require.Equal(t, newBlockMaxt, db.head.MinTime())

	// Another WAL file was rotated.
	first, last, err = wlog.Segments(db.head.wal.Dir())
	require.NoError(t, err)
	require.Equal(t, 40, first)
	require.Equal(t, 62, last)

	require.Equal(t, 0.0, prom_testutil.ToFloat64(db.head.metrics.checkpointCreationTotal))
	require.NoError(t, db.Compact(ctx))
	require.Equal(t, 1.0, prom_testutil.ToFloat64(db.head.metrics.checkpointCreationTotal))

	// No new blocks should be created as there was not data in between the new samples and the blocks.
	require.Len(t, db.Blocks(), 59)

	// The compaction should have only truncated first 2/3 of WAL (while also rotating the files).
	first, last, err = wlog.Segments(db.head.wal.Dir())
	require.NoError(t, err)
	require.Equal(t, 55, first)
	require.Equal(t, 63, last)

	// The first checkpoint would be for first 2/3rd of WAL, hence till 54.
	// That should be the last checkpoint.
	_, cno, err = wlog.LastCheckpoint(db.head.wal.Dir())
	require.NoError(t, err)
	require.Equal(t, 54, cno)
}

func TestNoPanicOnTSDBOpenError(t *testing.T) {
	tmpdir := t.TempDir()

	// Taking the lock will cause a TSDB startup error.
	l, err := tsdbutil.NewDirLocker(tmpdir, "tsdb", log.NewNopLogger(), nil)
	require.NoError(t, err)
	require.NoError(t, l.Lock())

	_, err = Open(tmpdir, nil, nil, DefaultOptions(), nil)
	require.Error(t, err)

	require.NoError(t, l.Release())
}

func TestLockfile(t *testing.T) {
	tsdbutil.TestDirLockerUsage(t, func(t *testing.T, data string, createLock bool) (*tsdbutil.DirLocker, testutil.Closer) {
		opts := DefaultOptions()
		opts.NoLockfile = !createLock

		// Create the DB. This should create lockfile and its metrics.
		db, err := Open(data, nil, nil, opts, nil)
		require.NoError(t, err)

		return db.locker, testutil.NewCallbackCloser(func() {
			require.NoError(t, db.Close())
		})
	})
}

func TestQuerier_ShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks(t *testing.T) {
	t.Skip("TODO: investigate why process crash in CI")

	const numRuns = 5

	for i := 1; i <= numRuns; i++ {
		t.Run(strconv.Itoa(i), func(t *testing.T) {
			testQuerierShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks(t)
		})
	}
}

func testQuerierShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks(t *testing.T) {
	const (
		numSeries                = 1000
		numStressIterations      = 10000
		minStressAllocationBytes = 128 * 1024
		maxStressAllocationBytes = 512 * 1024
	)

	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	// Disable compactions so we can control it.
	db.DisableCompactions()

	// Generate the metrics we're going to append.
	metrics := make([]labels.Labels, 0, numSeries)
	for i := 0; i < numSeries; i++ {
		metrics = append(metrics, labels.FromStrings(labels.MetricName, fmt.Sprintf("test_%d", i)))
	}

	// Push 1 sample every 15s for 2x the block duration period.
	ctx := context.Background()
	interval := int64(15 * time.Second / time.Millisecond)
	ts := int64(0)

	for ; ts < 2*DefaultBlockDuration; ts += interval {
		app := db.Appender(ctx)

		for _, metric := range metrics {
			_, err := app.Append(0, metric, ts, float64(ts))
			require.NoError(t, err)
		}

		require.NoError(t, app.Commit())
	}

	// Compact the TSDB head for the first time. We expect the head chunks file has been cut.
	require.NoError(t, db.Compact(ctx))
	require.Equal(t, float64(1), prom_testutil.ToFloat64(db.Head().metrics.headTruncateTotal))

	// Push more samples for another 1x block duration period.
	for ; ts < 3*DefaultBlockDuration; ts += interval {
		app := db.Appender(ctx)

		for _, metric := range metrics {
			_, err := app.Append(0, metric, ts, float64(ts))
			require.NoError(t, err)
		}

		require.NoError(t, app.Commit())
	}

	// At this point we expect 2 mmap-ed head chunks.

	// Get a querier and make sure it's closed only once the test is over.
	querier, err := db.Querier(0, math.MaxInt64)
	require.NoError(t, err)
	defer func() {
		require.NoError(t, querier.Close())
	}()

	// Query back all series.
	hints := &storage.SelectHints{Start: 0, End: math.MaxInt64, Step: interval}
	seriesSet := querier.Select(ctx, true, hints, labels.MustNewMatcher(labels.MatchRegexp, labels.MetricName, ".+"))

	// Fetch samples iterators from all series.
	var iterators []chunkenc.Iterator
	actualSeries := 0
	for seriesSet.Next() {
		actualSeries++

		// Get the iterator and call Next() so that we're sure the chunk is loaded.
		it := seriesSet.At().Iterator(nil)
		it.Next()
		it.At()

		iterators = append(iterators, it)
	}
	require.NoError(t, seriesSet.Err())
	require.Equal(t, numSeries, actualSeries)

	// Compact the TSDB head again.
	require.NoError(t, db.Compact(ctx))
	require.Equal(t, float64(2), prom_testutil.ToFloat64(db.Head().metrics.headTruncateTotal))

	// At this point we expect 1 head chunk has been deleted.

	// Stress the memory and call GC. This is required to increase the chances
	// the chunk memory area is released to the kernel.
	var buf []byte
	for i := 0; i < numStressIterations; i++ {
		//nolint:staticcheck
		buf = append(buf, make([]byte, minStressAllocationBytes+rand.Int31n(maxStressAllocationBytes-minStressAllocationBytes))...)
		if i%1000 == 0 {
			buf = nil
		}
	}

	// Iterate samples. Here we're summing it just to make sure no golang compiler
	// optimization triggers in case we discard the result of it.At().
	var sum float64
	var firstErr error
	for _, it := range iterators {
		for it.Next() == chunkenc.ValFloat {
			_, v := it.At()
			sum += v
		}

		if err := it.Err(); err != nil {
			firstErr = err
		}
	}

	// After having iterated all samples we also want to be sure no error occurred or
	// the "cannot populate chunk XXX: not found" error occurred. This error can occur
	// when the iterator tries to fetch an head chunk which has been offloaded because
	// of the head compaction in the meanwhile.
	if firstErr != nil {
		require.ErrorContains(t, firstErr, "cannot populate chunk")
	}
}

func TestChunkQuerier_ShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks(t *testing.T) {
	t.Skip("TODO: investigate why process crash in CI")

	const numRuns = 5

	for i := 1; i <= numRuns; i++ {
		t.Run(strconv.Itoa(i), func(t *testing.T) {
			testChunkQuerierShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks(t)
		})
	}
}

func testChunkQuerierShouldNotPanicIfHeadChunkIsTruncatedWhileReadingQueriedChunks(t *testing.T) {
	const (
		numSeries                = 1000
		numStressIterations      = 10000
		minStressAllocationBytes = 128 * 1024
		maxStressAllocationBytes = 512 * 1024
	)

	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	// Disable compactions so we can control it.
	db.DisableCompactions()

	// Generate the metrics we're going to append.
	metrics := make([]labels.Labels, 0, numSeries)
	for i := 0; i < numSeries; i++ {
		metrics = append(metrics, labels.FromStrings(labels.MetricName, fmt.Sprintf("test_%d", i)))
	}

	// Push 1 sample every 15s for 2x the block duration period.
	ctx := context.Background()
	interval := int64(15 * time.Second / time.Millisecond)
	ts := int64(0)

	for ; ts < 2*DefaultBlockDuration; ts += interval {
		app := db.Appender(ctx)

		for _, metric := range metrics {
			_, err := app.Append(0, metric, ts, float64(ts))
			require.NoError(t, err)
		}

		require.NoError(t, app.Commit())
	}

	// Compact the TSDB head for the first time. We expect the head chunks file has been cut.
	require.NoError(t, db.Compact(ctx))
	require.Equal(t, float64(1), prom_testutil.ToFloat64(db.Head().metrics.headTruncateTotal))

	// Push more samples for another 1x block duration period.
	for ; ts < 3*DefaultBlockDuration; ts += interval {
		app := db.Appender(ctx)

		for _, metric := range metrics {
			_, err := app.Append(0, metric, ts, float64(ts))
			require.NoError(t, err)
		}

		require.NoError(t, app.Commit())
	}

	// At this point we expect 2 mmap-ed head chunks.

	// Get a querier and make sure it's closed only once the test is over.
	querier, err := db.ChunkQuerier(0, math.MaxInt64)
	require.NoError(t, err)
	defer func() {
		require.NoError(t, querier.Close())
	}()

	// Query back all series.
	hints := &storage.SelectHints{Start: 0, End: math.MaxInt64, Step: interval}
	seriesSet := querier.Select(ctx, true, hints, labels.MustNewMatcher(labels.MatchRegexp, labels.MetricName, ".+"))

	// Iterate all series and get their chunks.
	var it chunks.Iterator
	var chunks []chunkenc.Chunk
	actualSeries := 0
	for seriesSet.Next() {
		actualSeries++
		it = seriesSet.At().Iterator(it)
		for it.Next() {
			chunks = append(chunks, it.At().Chunk)
		}
	}
	require.NoError(t, seriesSet.Err())
	require.Equal(t, numSeries, actualSeries)

	// Compact the TSDB head again.
	require.NoError(t, db.Compact(ctx))
	require.Equal(t, float64(2), prom_testutil.ToFloat64(db.Head().metrics.headTruncateTotal))

	// At this point we expect 1 head chunk has been deleted.

	// Stress the memory and call GC. This is required to increase the chances
	// the chunk memory area is released to the kernel.
	var buf []byte
	for i := 0; i < numStressIterations; i++ {
		//nolint:staticcheck
		buf = append(buf, make([]byte, minStressAllocationBytes+rand.Int31n(maxStressAllocationBytes-minStressAllocationBytes))...)
		if i%1000 == 0 {
			buf = nil
		}
	}

	// Iterate chunks and read their bytes slice. Here we're computing the CRC32
	// just to iterate through the bytes slice. We don't really care the reason why
	// we read this data, we just need to read it to make sure the memory address
	// of the []byte is still valid.
	chkCRC32 := newCRC32()
	for _, chunk := range chunks {
		chkCRC32.Reset()
		_, err := chkCRC32.Write(chunk.Bytes())
		require.NoError(t, err)
	}
}

func TestQuerierShouldNotFailIfOOOCompactionOccursAfterRetrievingQuerier(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 3 * DefaultBlockDuration
	db := openTestDB(t, opts, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	// Disable compactions so we can control it.
	db.DisableCompactions()

	metric := labels.FromStrings(labels.MetricName, "test_metric")
	ctx := context.Background()
	interval := int64(15 * time.Second / time.Millisecond)
	ts := int64(0)
	samplesWritten := 0

	// Capture the first timestamp - this will be the timestamp of the OOO sample we'll append below.
	oooTS := ts
	ts += interval

	// Push samples after the OOO sample we'll write below.
	for ; ts < 10*interval; ts += interval {
		app := db.Appender(ctx)
		_, err := app.Append(0, metric, ts, float64(ts))
		require.NoError(t, err)
		require.NoError(t, app.Commit())
		samplesWritten++
	}

	// Push a single OOO sample.
	app := db.Appender(ctx)
	_, err := app.Append(0, metric, oooTS, float64(ts))
	require.NoError(t, err)
	require.NoError(t, app.Commit())
	samplesWritten++

	// Get a querier.
	querierCreatedBeforeCompaction, err := db.ChunkQuerier(0, math.MaxInt64)
	require.NoError(t, err)

	// Start OOO head compaction.
	compactionComplete := atomic.NewBool(false)
	go func() {
		defer compactionComplete.Store(true)

		require.NoError(t, db.CompactOOOHead(ctx))
		require.Equal(t, float64(1), prom_testutil.ToFloat64(db.Head().metrics.chunksRemoved))
	}()

	// Give CompactOOOHead time to start work.
	// If it does not wait for querierCreatedBeforeCompaction to be closed, then the query will return incorrect results or fail.
	time.Sleep(time.Second)
	require.False(t, compactionComplete.Load(), "compaction completed before reading chunks or closing querier created before compaction")

	// Get another querier. This one should only use the compacted blocks from disk and ignore the chunks that will be garbage collected.
	querierCreatedAfterCompaction, err := db.ChunkQuerier(0, math.MaxInt64)
	require.NoError(t, err)

	testQuerier := func(q storage.ChunkQuerier) {
		// Query back the series.
		hints := &storage.SelectHints{Start: 0, End: math.MaxInt64, Step: interval}
		seriesSet := q.Select(ctx, true, hints, labels.MustNewMatcher(labels.MatchEqual, labels.MetricName, "test_metric"))

		// Collect the iterator for the series.
		var iterators []chunks.Iterator
		for seriesSet.Next() {
			iterators = append(iterators, seriesSet.At().Iterator(nil))
		}
		require.NoError(t, seriesSet.Err())
		require.Len(t, iterators, 1)
		iterator := iterators[0]

		// Check that we can still successfully read all samples.
		samplesRead := 0
		for iterator.Next() {
			samplesRead += iterator.At().Chunk.NumSamples()
		}

		require.NoError(t, iterator.Err())
		require.Equal(t, samplesWritten, samplesRead)
	}

	testQuerier(querierCreatedBeforeCompaction)

	require.False(t, compactionComplete.Load(), "compaction completed before closing querier created before compaction")
	require.NoError(t, querierCreatedBeforeCompaction.Close())
	require.Eventually(t, compactionComplete.Load, time.Second, 10*time.Millisecond, "compaction should complete after querier created before compaction was closed, and not wait for querier created after compaction")

	// Use the querier created after compaction and confirm it returns the expected results (ie. from the disk block created from OOO head and in-order head) without error.
	testQuerier(querierCreatedAfterCompaction)
	require.NoError(t, querierCreatedAfterCompaction.Close())
}

func TestQuerierShouldNotFailIfOOOCompactionOccursAfterSelecting(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 3 * DefaultBlockDuration
	db := openTestDB(t, opts, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	// Disable compactions so we can control it.
	db.DisableCompactions()

	metric := labels.FromStrings(labels.MetricName, "test_metric")
	ctx := context.Background()
	interval := int64(15 * time.Second / time.Millisecond)
	ts := int64(0)
	samplesWritten := 0

	// Capture the first timestamp - this will be the timestamp of the OOO sample we'll append below.
	oooTS := ts
	ts += interval

	// Push samples after the OOO sample we'll write below.
	for ; ts < 10*interval; ts += interval {
		app := db.Appender(ctx)
		_, err := app.Append(0, metric, ts, float64(ts))
		require.NoError(t, err)
		require.NoError(t, app.Commit())
		samplesWritten++
	}

	// Push a single OOO sample.
	app := db.Appender(ctx)
	_, err := app.Append(0, metric, oooTS, float64(ts))
	require.NoError(t, err)
	require.NoError(t, app.Commit())
	samplesWritten++

	// Get a querier.
	querier, err := db.ChunkQuerier(0, math.MaxInt64)
	require.NoError(t, err)

	// Query back the series.
	hints := &storage.SelectHints{Start: 0, End: math.MaxInt64, Step: interval}
	seriesSet := querier.Select(ctx, true, hints, labels.MustNewMatcher(labels.MatchEqual, labels.MetricName, "test_metric"))

	// Start OOO head compaction.
	compactionComplete := atomic.NewBool(false)
	go func() {
		defer compactionComplete.Store(true)

		require.NoError(t, db.CompactOOOHead(ctx))
		require.Equal(t, float64(1), prom_testutil.ToFloat64(db.Head().metrics.chunksRemoved))
	}()

	// Give CompactOOOHead time to start work.
	// If it does not wait for the querier to be closed, then the query will return incorrect results or fail.
	time.Sleep(time.Second)
	require.False(t, compactionComplete.Load(), "compaction completed before reading chunks or closing querier")

	// Collect the iterator for the series.
	var iterators []chunks.Iterator
	for seriesSet.Next() {
		iterators = append(iterators, seriesSet.At().Iterator(nil))
	}
	require.NoError(t, seriesSet.Err())
	require.Len(t, iterators, 1)
	iterator := iterators[0]

	// Check that we can still successfully read all samples.
	samplesRead := 0
	for iterator.Next() {
		samplesRead += iterator.At().Chunk.NumSamples()
	}

	require.NoError(t, iterator.Err())
	require.Equal(t, samplesWritten, samplesRead)

	require.False(t, compactionComplete.Load(), "compaction completed before closing querier")
	require.NoError(t, querier.Close())
	require.Eventually(t, compactionComplete.Load, time.Second, 10*time.Millisecond, "compaction should complete after querier was closed")
}

func TestQuerierShouldNotFailIfOOOCompactionOccursAfterRetrievingIterators(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 3 * DefaultBlockDuration
	db := openTestDB(t, opts, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	// Disable compactions so we can control it.
	db.DisableCompactions()

	metric := labels.FromStrings(labels.MetricName, "test_metric")
	ctx := context.Background()
	interval := int64(15 * time.Second / time.Millisecond)
	ts := int64(0)
	samplesWritten := 0

	// Capture the first timestamp - this will be the timestamp of the OOO sample we'll append below.
	oooTS := ts
	ts += interval

	// Push samples after the OOO sample we'll write below.
	for ; ts < 10*interval; ts += interval {
		app := db.Appender(ctx)
		_, err := app.Append(0, metric, ts, float64(ts))
		require.NoError(t, err)
		require.NoError(t, app.Commit())
		samplesWritten++
	}

	// Push a single OOO sample.
	app := db.Appender(ctx)
	_, err := app.Append(0, metric, oooTS, float64(ts))
	require.NoError(t, err)
	require.NoError(t, app.Commit())
	samplesWritten++

	// Get a querier.
	querier, err := db.ChunkQuerier(0, math.MaxInt64)
	require.NoError(t, err)

	// Query back the series.
	hints := &storage.SelectHints{Start: 0, End: math.MaxInt64, Step: interval}
	seriesSet := querier.Select(ctx, true, hints, labels.MustNewMatcher(labels.MatchEqual, labels.MetricName, "test_metric"))

	// Collect the iterator for the series.
	var iterators []chunks.Iterator
	for seriesSet.Next() {
		iterators = append(iterators, seriesSet.At().Iterator(nil))
	}
	require.NoError(t, seriesSet.Err())
	require.Len(t, iterators, 1)
	iterator := iterators[0]

	// Start OOO head compaction.
	compactionComplete := atomic.NewBool(false)
	go func() {
		defer compactionComplete.Store(true)

		require.NoError(t, db.CompactOOOHead(ctx))
		require.Equal(t, float64(1), prom_testutil.ToFloat64(db.Head().metrics.chunksRemoved))
	}()

	// Give CompactOOOHead time to start work.
	// If it does not wait for the querier to be closed, then the query will return incorrect results or fail.
	time.Sleep(time.Second)
	require.False(t, compactionComplete.Load(), "compaction completed before reading chunks or closing querier")

	// Check that we can still successfully read all samples.
	samplesRead := 0
	for iterator.Next() {
		samplesRead += iterator.At().Chunk.NumSamples()
	}

	require.NoError(t, iterator.Err())
	require.Equal(t, samplesWritten, samplesRead)

	require.False(t, compactionComplete.Load(), "compaction completed before closing querier")
	require.NoError(t, querier.Close())
	require.Eventually(t, compactionComplete.Load, time.Second, 10*time.Millisecond, "compaction should complete after querier was closed")
}

func newTestDB(t *testing.T) *DB {
	dir := t.TempDir()

	db, err := Open(dir, nil, nil, DefaultOptions(), nil)
	require.NoError(t, err)
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})
	return db
}

func TestOOOWALWrite(t *testing.T) {
	dir := t.TempDir()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 2
	opts.OutOfOrderTimeWindow = 30 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)

	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	s1, s2 := labels.FromStrings("l", "v1"), labels.FromStrings("l", "v2")
	minutes := func(m int64) int64 { return m * time.Minute.Milliseconds() }

	appendSample := func(app storage.Appender, l labels.Labels, mins int64) {
		_, err = app.Append(0, l, minutes(mins), float64(mins))
		require.NoError(t, err)
	}

	// Ingest sample at 1h.
	app := db.Appender(context.Background())
	appendSample(app, s1, 60)
	appendSample(app, s2, 60)
	require.NoError(t, app.Commit())

	// OOO for s1.
	app = db.Appender(context.Background())
	appendSample(app, s1, 40)
	require.NoError(t, app.Commit())

	// OOO for s2.
	app = db.Appender(context.Background())
	appendSample(app, s2, 42)
	require.NoError(t, app.Commit())

	// OOO for both s1 and s2 in the same commit.
	app = db.Appender(context.Background())
	appendSample(app, s2, 45)
	appendSample(app, s1, 35)
	appendSample(app, s1, 36) // m-maps.
	appendSample(app, s1, 37)
	require.NoError(t, app.Commit())

	// OOO for s1 but not for s2 in the same commit.
	app = db.Appender(context.Background())
	appendSample(app, s1, 50) // m-maps.
	appendSample(app, s2, 65)
	require.NoError(t, app.Commit())

	// Single commit has 2 times m-mapping and more samples after m-map.
	app = db.Appender(context.Background())
	appendSample(app, s2, 50) // m-maps.
	appendSample(app, s2, 51)
	appendSample(app, s2, 52) // m-maps.
	appendSample(app, s2, 53)
	require.NoError(t, app.Commit())

	// The MmapRef in this are not hand calculated, and instead taken from the test run.
	// What is important here is the order of records, and that MmapRef increases for each record.
	oooRecords := []interface{}{
		[]record.RefMmapMarker{
			{Ref: 1},
		},
		[]record.RefSample{
			{Ref: 1, T: minutes(40), V: 40},
		},

		[]record.RefMmapMarker{
			{Ref: 2},
		},
		[]record.RefSample{
			{Ref: 2, T: minutes(42), V: 42},
		},

		[]record.RefSample{
			{Ref: 2, T: minutes(45), V: 45},
			{Ref: 1, T: minutes(35), V: 35},
		},
		[]record.RefMmapMarker{ // 3rd sample, hence m-mapped.
			{Ref: 1, MmapRef: 4294967304},
		},
		[]record.RefSample{
			{Ref: 1, T: minutes(36), V: 36},
			{Ref: 1, T: minutes(37), V: 37},
		},

		[]record.RefMmapMarker{ // 3rd sample, hence m-mapped.
			{Ref: 1, MmapRef: 4294967354},
		},
		[]record.RefSample{ // Does not contain the in-order sample here.
			{Ref: 1, T: minutes(50), V: 50},
		},

		// Single commit but multiple OOO records.
		[]record.RefMmapMarker{
			{Ref: 2, MmapRef: 4294967403},
		},
		[]record.RefSample{
			{Ref: 2, T: minutes(50), V: 50},
			{Ref: 2, T: minutes(51), V: 51},
		},
		[]record.RefMmapMarker{
			{Ref: 2, MmapRef: 4294967452},
		},
		[]record.RefSample{
			{Ref: 2, T: minutes(52), V: 52},
			{Ref: 2, T: minutes(53), V: 53},
		},
	}

	inOrderRecords := []interface{}{
		[]record.RefSeries{
			{Ref: 1, Labels: s1},
			{Ref: 2, Labels: s2},
		},
		[]record.RefSample{
			{Ref: 1, T: minutes(60), V: 60},
			{Ref: 2, T: minutes(60), V: 60},
		},
		[]record.RefSample{
			{Ref: 1, T: minutes(40), V: 40},
		},
		[]record.RefSample{
			{Ref: 2, T: minutes(42), V: 42},
		},
		[]record.RefSample{
			{Ref: 2, T: minutes(45), V: 45},
			{Ref: 1, T: minutes(35), V: 35},
			{Ref: 1, T: minutes(36), V: 36},
			{Ref: 1, T: minutes(37), V: 37},
		},
		[]record.RefSample{ // Contains both in-order and ooo sample.
			{Ref: 1, T: minutes(50), V: 50},
			{Ref: 2, T: minutes(65), V: 65},
		},
		[]record.RefSample{
			{Ref: 2, T: minutes(50), V: 50},
			{Ref: 2, T: minutes(51), V: 51},
			{Ref: 2, T: minutes(52), V: 52},
			{Ref: 2, T: minutes(53), V: 53},
		},
	}

	getRecords := func(walDir string) []interface{} {
		sr, err := wlog.NewSegmentsReader(walDir)
		require.NoError(t, err)
		r := wlog.NewReader(sr)
		defer func() {
			require.NoError(t, sr.Close())
		}()

		var (
			records []interface{}
			dec     record.Decoder = record.NewDecoder(labels.NewSymbolTable())
		)
		for r.Next() {
			rec := r.Record()
			switch typ := dec.Type(rec); typ {
			case record.Series:
				series, err := dec.Series(rec, nil)
				require.NoError(t, err)
				records = append(records, series)
			case record.Samples:
				samples, err := dec.Samples(rec, nil)
				require.NoError(t, err)
				records = append(records, samples)
			case record.MmapMarkers:
				markers, err := dec.MmapMarkers(rec, nil)
				require.NoError(t, err)
				records = append(records, markers)
			default:
				t.Fatalf("got a WAL record that is not series or samples: %v", typ)
			}
		}

		return records
	}

	// The normal WAL.
	actRecs := getRecords(path.Join(dir, "wal"))
	testutil.RequireEqual(t, inOrderRecords, actRecs)

	// The WBL.
	actRecs = getRecords(path.Join(dir, wlog.WblDirName))
	testutil.RequireEqual(t, oooRecords, actRecs)
}

// Tests https://github.com/prometheus/prometheus/issues/10291#issuecomment-1044373110.
func TestDBPanicOnMmappingHeadChunk(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	db, err := Open(dir, nil, nil, DefaultOptions(), nil)
	require.NoError(t, err)
	db.DisableCompactions()

	// Choosing scrape interval of 45s to have chunk larger than 1h.
	itvl := int64(45 * time.Second / time.Millisecond)

	lastTs := int64(0)
	addSamples := func(numSamples int) {
		app := db.Appender(context.Background())
		var ref storage.SeriesRef
		lbls := labels.FromStrings("__name__", "testing", "foo", "bar")
		for i := 0; i < numSamples; i++ {
			ref, err = app.Append(ref, lbls, lastTs, float64(lastTs))
			require.NoError(t, err)
			lastTs += itvl
			if i%10 == 0 {
				require.NoError(t, app.Commit())
				app = db.Appender(context.Background())
			}
		}
		require.NoError(t, app.Commit())
	}

	// Ingest samples upto 2h50m to make the head "about to compact".
	numSamples := int(170*time.Minute/time.Millisecond) / int(itvl)
	addSamples(numSamples)

	require.Empty(t, db.Blocks())
	require.NoError(t, db.Compact(ctx))
	require.Empty(t, db.Blocks())

	// Restarting.
	require.NoError(t, db.Close())

	db, err = Open(dir, nil, nil, DefaultOptions(), nil)
	require.NoError(t, err)
	db.DisableCompactions()

	// Ingest samples upto 20m more to make the head compact.
	numSamples = int(20*time.Minute/time.Millisecond) / int(itvl)
	addSamples(numSamples)

	require.Empty(t, db.Blocks())
	require.NoError(t, db.Compact(ctx))
	require.Len(t, db.Blocks(), 1)

	// More samples to m-map and panic.
	numSamples = int(120*time.Minute/time.Millisecond) / int(itvl)
	addSamples(numSamples)

	require.NoError(t, db.Close())
}

func TestMetadataInWAL(t *testing.T) {
	updateMetadata := func(t *testing.T, app storage.Appender, s labels.Labels, m metadata.Metadata) {
		_, err := app.UpdateMetadata(0, s, m)
		require.NoError(t, err)
	}

	db := newTestDB(t)
	ctx := context.Background()

	// Add some series so we can append metadata to them.
	app := db.Appender(ctx)
	s1 := labels.FromStrings("a", "b")
	s2 := labels.FromStrings("c", "d")
	s3 := labels.FromStrings("e", "f")
	s4 := labels.FromStrings("g", "h")

	for _, s := range []labels.Labels{s1, s2, s3, s4} {
		_, err := app.Append(0, s, 0, 0)
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	// Add a first round of metadata to the first three series.
	// Re-take the Appender, as the previous Commit will have it closed.
	m1 := metadata.Metadata{Type: "gauge", Unit: "unit_1", Help: "help_1"}
	m2 := metadata.Metadata{Type: "gauge", Unit: "unit_2", Help: "help_2"}
	m3 := metadata.Metadata{Type: "gauge", Unit: "unit_3", Help: "help_3"}
	app = db.Appender(ctx)
	updateMetadata(t, app, s1, m1)
	updateMetadata(t, app, s2, m2)
	updateMetadata(t, app, s3, m3)
	require.NoError(t, app.Commit())

	// Add a replicated metadata entry to the first series,
	// a completely new metadata entry for the fourth series,
	// and a changed metadata entry to the second series.
	m4 := metadata.Metadata{Type: "counter", Unit: "unit_4", Help: "help_4"}
	m5 := metadata.Metadata{Type: "counter", Unit: "unit_5", Help: "help_5"}
	app = db.Appender(ctx)
	updateMetadata(t, app, s1, m1)
	updateMetadata(t, app, s4, m4)
	updateMetadata(t, app, s2, m5)
	require.NoError(t, app.Commit())

	// Read the WAL to see if the disk storage format is correct.
	recs := readTestWAL(t, path.Join(db.Dir(), "wal"))
	var gotMetadataBlocks [][]record.RefMetadata
	for _, rec := range recs {
		if mr, ok := rec.([]record.RefMetadata); ok {
			gotMetadataBlocks = append(gotMetadataBlocks, mr)
		}
	}

	expectedMetadata := []record.RefMetadata{
		{Ref: 1, Type: record.GetMetricType(m1.Type), Unit: m1.Unit, Help: m1.Help},
		{Ref: 2, Type: record.GetMetricType(m2.Type), Unit: m2.Unit, Help: m2.Help},
		{Ref: 3, Type: record.GetMetricType(m3.Type), Unit: m3.Unit, Help: m3.Help},
		{Ref: 4, Type: record.GetMetricType(m4.Type), Unit: m4.Unit, Help: m4.Help},
		{Ref: 2, Type: record.GetMetricType(m5.Type), Unit: m5.Unit, Help: m5.Help},
	}
	require.Len(t, gotMetadataBlocks, 2)
	require.Equal(t, expectedMetadata[:3], gotMetadataBlocks[0])
	require.Equal(t, expectedMetadata[3:], gotMetadataBlocks[1])
}

func TestMetadataCheckpointingOnlyKeepsLatestEntry(t *testing.T) {
	updateMetadata := func(t *testing.T, app storage.Appender, s labels.Labels, m metadata.Metadata) {
		_, err := app.UpdateMetadata(0, s, m)
		require.NoError(t, err)
	}

	ctx := context.Background()
	numSamples := 10000
	hb, w := newTestHead(t, int64(numSamples)*10, wlog.CompressionNone, false)

	// Add some series so we can append metadata to them.
	app := hb.Appender(ctx)
	s1 := labels.FromStrings("a", "b")
	s2 := labels.FromStrings("c", "d")
	s3 := labels.FromStrings("e", "f")
	s4 := labels.FromStrings("g", "h")

	for _, s := range []labels.Labels{s1, s2, s3, s4} {
		_, err := app.Append(0, s, 0, 0)
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	// Add a first round of metadata to the first three series.
	// Re-take the Appender, as the previous Commit will have it closed.
	m1 := metadata.Metadata{Type: "gauge", Unit: "unit_1", Help: "help_1"}
	m2 := metadata.Metadata{Type: "gauge", Unit: "unit_2", Help: "help_2"}
	m3 := metadata.Metadata{Type: "gauge", Unit: "unit_3", Help: "help_3"}
	m4 := metadata.Metadata{Type: "gauge", Unit: "unit_4", Help: "help_4"}
	app = hb.Appender(ctx)
	updateMetadata(t, app, s1, m1)
	updateMetadata(t, app, s2, m2)
	updateMetadata(t, app, s3, m3)
	updateMetadata(t, app, s4, m4)
	require.NoError(t, app.Commit())

	// Update metadata for first series.
	m5 := metadata.Metadata{Type: "counter", Unit: "unit_5", Help: "help_5"}
	app = hb.Appender(ctx)
	updateMetadata(t, app, s1, m5)
	require.NoError(t, app.Commit())

	// Switch back-and-forth metadata for second series.
	// Since it ended on a new metadata record, we expect a single new entry.
	m6 := metadata.Metadata{Type: "counter", Unit: "unit_6", Help: "help_6"}

	app = hb.Appender(ctx)
	updateMetadata(t, app, s2, m6)
	require.NoError(t, app.Commit())

	app = hb.Appender(ctx)
	updateMetadata(t, app, s2, m2)
	require.NoError(t, app.Commit())

	app = hb.Appender(ctx)
	updateMetadata(t, app, s2, m6)
	require.NoError(t, app.Commit())

	app = hb.Appender(ctx)
	updateMetadata(t, app, s2, m2)
	require.NoError(t, app.Commit())

	app = hb.Appender(ctx)
	updateMetadata(t, app, s2, m6)
	require.NoError(t, app.Commit())

	// Let's create a checkpoint.
	first, last, err := wlog.Segments(w.Dir())
	require.NoError(t, err)
	keep := func(id chunks.HeadSeriesRef) bool {
		return id != 3
	}
	_, err = wlog.Checkpoint(log.NewNopLogger(), w, first, last-1, keep, 0)
	require.NoError(t, err)

	// Confirm there's been a checkpoint.
	cdir, _, err := wlog.LastCheckpoint(w.Dir())
	require.NoError(t, err)

	// Read in checkpoint and WAL.
	recs := readTestWAL(t, cdir)
	var gotMetadataBlocks [][]record.RefMetadata
	for _, rec := range recs {
		if mr, ok := rec.([]record.RefMetadata); ok {
			gotMetadataBlocks = append(gotMetadataBlocks, mr)
		}
	}

	// There should only be 1 metadata block present, with only the latest
	// metadata kept around.
	wantMetadata := []record.RefMetadata{
		{Ref: 1, Type: record.GetMetricType(m5.Type), Unit: m5.Unit, Help: m5.Help},
		{Ref: 2, Type: record.GetMetricType(m6.Type), Unit: m6.Unit, Help: m6.Help},
		{Ref: 4, Type: record.GetMetricType(m4.Type), Unit: m4.Unit, Help: m4.Help},
	}
	require.Len(t, gotMetadataBlocks, 1)
	require.Len(t, gotMetadataBlocks[0], 3)
	gotMetadataBlock := gotMetadataBlocks[0]

	sort.Slice(gotMetadataBlock, func(i, j int) bool { return gotMetadataBlock[i].Ref < gotMetadataBlock[j].Ref })
	require.Equal(t, wantMetadata, gotMetadataBlock)
	require.NoError(t, hb.Close())
}

func TestMetadataAssertInMemoryData(t *testing.T) {
	updateMetadata := func(t *testing.T, app storage.Appender, s labels.Labels, m metadata.Metadata) {
		_, err := app.UpdateMetadata(0, s, m)
		require.NoError(t, err)
	}

	db := openTestDB(t, nil, nil)
	ctx := context.Background()

	// Add some series so we can append metadata to them.
	app := db.Appender(ctx)
	s1 := labels.FromStrings("a", "b")
	s2 := labels.FromStrings("c", "d")
	s3 := labels.FromStrings("e", "f")
	s4 := labels.FromStrings("g", "h")

	for _, s := range []labels.Labels{s1, s2, s3, s4} {
		_, err := app.Append(0, s, 0, 0)
		require.NoError(t, err)
	}
	require.NoError(t, app.Commit())

	// Add a first round of metadata to the first three series.
	// The in-memory data held in the db Head should hold the metadata.
	m1 := metadata.Metadata{Type: "gauge", Unit: "unit_1", Help: "help_1"}
	m2 := metadata.Metadata{Type: "gauge", Unit: "unit_2", Help: "help_2"}
	m3 := metadata.Metadata{Type: "gauge", Unit: "unit_3", Help: "help_3"}
	app = db.Appender(ctx)
	updateMetadata(t, app, s1, m1)
	updateMetadata(t, app, s2, m2)
	updateMetadata(t, app, s3, m3)
	require.NoError(t, app.Commit())

	series1 := db.head.series.getByHash(s1.Hash(), s1)
	series2 := db.head.series.getByHash(s2.Hash(), s2)
	series3 := db.head.series.getByHash(s3.Hash(), s3)
	series4 := db.head.series.getByHash(s4.Hash(), s4)
	require.Equal(t, *series1.meta, m1)
	require.Equal(t, *series2.meta, m2)
	require.Equal(t, *series3.meta, m3)
	require.Nil(t, series4.meta)

	// Add a replicated metadata entry to the first series,
	// a changed metadata entry to the second series,
	// and a completely new metadata entry for the fourth series.
	// The in-memory data held in the db Head should be correctly updated.
	m4 := metadata.Metadata{Type: "counter", Unit: "unit_4", Help: "help_4"}
	m5 := metadata.Metadata{Type: "counter", Unit: "unit_5", Help: "help_5"}
	app = db.Appender(ctx)
	updateMetadata(t, app, s1, m1)
	updateMetadata(t, app, s4, m4)
	updateMetadata(t, app, s2, m5)
	require.NoError(t, app.Commit())

	series1 = db.head.series.getByHash(s1.Hash(), s1)
	series2 = db.head.series.getByHash(s2.Hash(), s2)
	series3 = db.head.series.getByHash(s3.Hash(), s3)
	series4 = db.head.series.getByHash(s4.Hash(), s4)
	require.Equal(t, *series1.meta, m1)
	require.Equal(t, *series2.meta, m5)
	require.Equal(t, *series3.meta, m3)
	require.Equal(t, *series4.meta, m4)

	require.NoError(t, db.Close())

	// Reopen the DB, replaying the WAL. The Head must have been replayed
	// correctly in memory.
	reopenDB, err := Open(db.Dir(), nil, nil, nil, nil)
	require.NoError(t, err)
	t.Cleanup(func() {
		require.NoError(t, reopenDB.Close())
	})

	_, err = reopenDB.head.wal.Size()
	require.NoError(t, err)

	require.Equal(t, *reopenDB.head.series.getByHash(s1.Hash(), s1).meta, m1)
	require.Equal(t, *reopenDB.head.series.getByHash(s2.Hash(), s2).meta, m5)
	require.Equal(t, *reopenDB.head.series.getByHash(s3.Hash(), s3).meta, m3)
	require.Equal(t, *reopenDB.head.series.getByHash(s4.Hash(), s4).meta, m4)
}

// TODO(codesome): test more samples incoming once compaction has started. To verify new samples after the start
//
//	are not included in this compaction.
func TestOOOCompaction(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions() // We want to manually call it.
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	series2 := labels.FromStrings("foo", "bar2")

	addSample := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			_, err = app.Append(0, series2, ts, float64(2*ts))
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSample(250, 350)

	// Verify that the in-memory ooo chunk is empty.
	checkEmptyOOOChunk := func(lbls labels.Labels) {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Nil(t, ms.ooo)
	}
	checkEmptyOOOChunk(series1)
	checkEmptyOOOChunk(series2)

	// Add ooo samples that creates multiple chunks.
	// 90 to 300 spans across 3 block ranges: [0, 120), [120, 240), [240, 360)
	addSample(90, 310)
	// Adding same samples to create overlapping chunks.
	// Since the active chunk won't start at 90 again, all the new
	// chunks will have different time ranges than the previous chunks.
	addSample(90, 310)

	verifyDBSamples := func() {
		var series1Samples, series2Samples []chunks.Sample
		for _, r := range [][2]int64{{90, 119}, {120, 239}, {240, 350}} {
			fromMins, toMins := r[0], r[1]
			for min := fromMins; min <= toMins; min++ {
				ts := min * time.Minute.Milliseconds()
				series1Samples = append(series1Samples, sample{ts, float64(ts), nil, nil})
				series2Samples = append(series2Samples, sample{ts, float64(2 * ts), nil, nil})
			}
		}
		expRes := map[string][]chunks.Sample{
			series1.String(): series1Samples,
			series2.String(): series2Samples,
		}

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	verifyDBSamples() // Before any compaction.

	// Verify that the in-memory ooo chunk is not empty.
	checkNonEmptyOOOChunk := func(lbls labels.Labels) {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Greater(t, ms.ooo.oooHeadChunk.chunk.NumSamples(), 0)
		require.Len(t, ms.ooo.oooMmappedChunks, 14) // 7 original, 7 duplicate.
	}
	checkNonEmptyOOOChunk(series1)
	checkNonEmptyOOOChunk(series2)

	// No blocks before compaction.
	require.Empty(t, db.Blocks())

	// There is a 0th WBL file.
	require.NoError(t, db.head.wbl.Sync()) // syncing to make sure wbl is flushed in windows
	files, err := os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 1)
	require.Equal(t, "00000000", files[0].Name())
	f, err := files[0].Info()
	require.NoError(t, err)
	require.Greater(t, f.Size(), int64(100))

	// OOO compaction happens here.
	require.NoError(t, db.CompactOOOHead(ctx))

	// 3 blocks exist now. [0, 120), [120, 240), [240, 360)
	require.Len(t, db.Blocks(), 3)

	verifyDBSamples() // Blocks created out of OOO head now.

	// 0th WBL file will be deleted and 1st will be the only present.
	files, err = os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 1)
	require.Equal(t, "00000001", files[0].Name())
	f, err = files[0].Info()
	require.NoError(t, err)
	require.Equal(t, int64(0), f.Size())

	// OOO stuff should not be present in the Head now.
	checkEmptyOOOChunk(series1)
	checkEmptyOOOChunk(series2)

	verifySamples := func(block *Block, fromMins, toMins int64) {
		series1Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		series2Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			series1Samples = append(series1Samples, sample{ts, float64(ts), nil, nil})
			series2Samples = append(series2Samples, sample{ts, float64(2 * ts), nil, nil})
		}
		expRes := map[string][]chunks.Sample{
			series1.String(): series1Samples,
			series2.String(): series2Samples,
		}

		q, err := NewBlockQuerier(block, math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	// Checking for expected data in the blocks.
	verifySamples(db.Blocks()[0], 90, 119)
	verifySamples(db.Blocks()[1], 120, 239)
	verifySamples(db.Blocks()[2], 240, 310)

	// There should be a single m-map file.
	mmapDir := mmappedChunksDir(db.head.opts.ChunkDirRoot)
	files, err = os.ReadDir(mmapDir)
	require.NoError(t, err)
	require.Len(t, files, 1)

	// Compact the in-order head and expect another block.
	// Since this is a forced compaction, this block is not aligned with 2h.
	err = db.CompactHead(NewRangeHead(db.head, 250*time.Minute.Milliseconds(), 350*time.Minute.Milliseconds()))
	require.NoError(t, err)
	require.Len(t, db.Blocks(), 4) // [0, 120), [120, 240), [240, 360), [250, 351)
	verifySamples(db.Blocks()[3], 250, 350)

	verifyDBSamples() // Blocks created out of normal and OOO head now. But not merged.

	// The compaction also clears out the old m-map files. Including
	// the file that has ooo chunks.
	files, err = os.ReadDir(mmapDir)
	require.NoError(t, err)
	require.Len(t, files, 1)
	require.Equal(t, "000001", files[0].Name())

	// This will merge overlapping block.
	require.NoError(t, db.Compact(ctx))

	require.Len(t, db.Blocks(), 3) // [0, 120), [120, 240), [240, 360)
	verifySamples(db.Blocks()[0], 90, 119)
	verifySamples(db.Blocks()[1], 120, 239)
	verifySamples(db.Blocks()[2], 240, 350) // Merged block.

	verifyDBSamples() // Final state. Blocks from normal and OOO head are merged.
}

// TestOOOCompactionWithNormalCompaction tests if OOO compaction is performed
// when the normal head's compaction is done.
func TestOOOCompactionWithNormalCompaction(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions() // We want to manually call it.
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	series2 := labels.FromStrings("foo", "bar2")

	addSamples := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			_, err = app.Append(0, series2, ts, float64(2*ts))
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSamples(250, 350)

	// Add ooo samples that will result into a single block.
	addSamples(90, 110)

	// Checking that ooo chunk is not empty.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Greater(t, ms.ooo.oooHeadChunk.chunk.NumSamples(), 0)
	}

	// If the normal Head is not compacted, the OOO head compaction does not take place.
	require.NoError(t, db.Compact(ctx))
	require.Empty(t, db.Blocks())

	// Add more in-order samples in future that would trigger the compaction.
	addSamples(400, 450)

	// No blocks before compaction.
	require.Empty(t, db.Blocks())

	// Compacts normal and OOO head.
	require.NoError(t, db.Compact(ctx))

	// 2 blocks exist now. [0, 120), [250, 360)
	require.Len(t, db.Blocks(), 2)
	require.Equal(t, int64(0), db.Blocks()[0].MinTime())
	require.Equal(t, 120*time.Minute.Milliseconds(), db.Blocks()[0].MaxTime())
	require.Equal(t, 250*time.Minute.Milliseconds(), db.Blocks()[1].MinTime())
	require.Equal(t, 360*time.Minute.Milliseconds(), db.Blocks()[1].MaxTime())

	// Checking that ooo chunk is empty.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Nil(t, ms.ooo)
	}

	verifySamples := func(block *Block, fromMins, toMins int64) {
		series1Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		series2Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			series1Samples = append(series1Samples, sample{ts, float64(ts), nil, nil})
			series2Samples = append(series2Samples, sample{ts, float64(2 * ts), nil, nil})
		}
		expRes := map[string][]chunks.Sample{
			series1.String(): series1Samples,
			series2.String(): series2Samples,
		}

		q, err := NewBlockQuerier(block, math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	// Checking for expected data in the blocks.
	verifySamples(db.Blocks()[0], 90, 110)
	verifySamples(db.Blocks()[1], 250, 350)
}

// TestOOOCompactionWithDisabledWriteLog tests the scenario where the TSDB is
// configured to not have wal and wbl but its able to compact both the in-order
// and out-of-order head.
func TestOOOCompactionWithDisabledWriteLog(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()
	opts.WALSegmentSize = -1 // disabled WAL and WBL

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions() // We want to manually call it.
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	series2 := labels.FromStrings("foo", "bar2")

	addSamples := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			_, err = app.Append(0, series2, ts, float64(2*ts))
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSamples(250, 350)

	// Add ooo samples that will result into a single block.
	addSamples(90, 110)

	// Checking that ooo chunk is not empty.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Greater(t, ms.ooo.oooHeadChunk.chunk.NumSamples(), 0)
	}

	// If the normal Head is not compacted, the OOO head compaction does not take place.
	require.NoError(t, db.Compact(ctx))
	require.Empty(t, db.Blocks())

	// Add more in-order samples in future that would trigger the compaction.
	addSamples(400, 450)

	// No blocks before compaction.
	require.Empty(t, db.Blocks())

	// Compacts normal and OOO head.
	require.NoError(t, db.Compact(ctx))

	// 2 blocks exist now. [0, 120), [250, 360)
	require.Len(t, db.Blocks(), 2)
	require.Equal(t, int64(0), db.Blocks()[0].MinTime())
	require.Equal(t, 120*time.Minute.Milliseconds(), db.Blocks()[0].MaxTime())
	require.Equal(t, 250*time.Minute.Milliseconds(), db.Blocks()[1].MinTime())
	require.Equal(t, 360*time.Minute.Milliseconds(), db.Blocks()[1].MaxTime())

	// Checking that ooo chunk is empty.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Nil(t, ms.ooo)
	}

	verifySamples := func(block *Block, fromMins, toMins int64) {
		series1Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		series2Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			series1Samples = append(series1Samples, sample{ts, float64(ts), nil, nil})
			series2Samples = append(series2Samples, sample{ts, float64(2 * ts), nil, nil})
		}
		expRes := map[string][]chunks.Sample{
			series1.String(): series1Samples,
			series2.String(): series2Samples,
		}

		q, err := NewBlockQuerier(block, math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	// Checking for expected data in the blocks.
	verifySamples(db.Blocks()[0], 90, 110)
	verifySamples(db.Blocks()[1], 250, 350)
}

// TestOOOQueryAfterRestartWithSnapshotAndRemovedWBL tests the scenario where the WBL goes
// missing after a restart while snapshot was enabled, but the query still returns the right
// data from the mmap chunks.
func TestOOOQueryAfterRestartWithSnapshotAndRemovedWBL(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 10
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()
	opts.EnableMemorySnapshotOnShutdown = true

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions() // We want to manually call it.
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	series2 := labels.FromStrings("foo", "bar2")

	addSamples := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			_, err = app.Append(0, series2, ts, float64(2*ts))
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSamples(250, 350)

	// Add ooo samples that will result into a single block.
	addSamples(90, 110) // The sample 110 will not be in m-map chunks.

	// Checking that there are some ooo m-map chunks.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Len(t, ms.ooo.oooMmappedChunks, 2)
		require.NotNil(t, ms.ooo.oooHeadChunk)
	}

	// Restart DB.
	require.NoError(t, db.Close())

	// For some reason wbl goes missing.
	require.NoError(t, os.RemoveAll(path.Join(dir, "wbl")))

	db, err = Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions() // We want to manually call it.

	// Check ooo m-map chunks again.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Len(t, ms.ooo.oooMmappedChunks, 2)
		require.Equal(t, 109*time.Minute.Milliseconds(), ms.ooo.oooMmappedChunks[1].maxTime)
		require.Nil(t, ms.ooo.oooHeadChunk) // Because of missing wbl.
	}

	verifySamples := func(fromMins, toMins int64) {
		series1Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		series2Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			series1Samples = append(series1Samples, sample{ts, float64(ts), nil, nil})
			series2Samples = append(series2Samples, sample{ts, float64(2 * ts), nil, nil})
		}
		expRes := map[string][]chunks.Sample{
			series1.String(): series1Samples,
			series2.String(): series2Samples,
		}

		q, err := db.Querier(fromMins*time.Minute.Milliseconds(), toMins*time.Minute.Milliseconds())
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	// Checking for expected ooo data from mmap chunks.
	verifySamples(90, 109)

	// Compaction should also work fine.
	require.Empty(t, db.Blocks())
	require.NoError(t, db.CompactOOOHead(ctx))
	require.Len(t, db.Blocks(), 1) // One block from OOO data.
	require.Equal(t, int64(0), db.Blocks()[0].MinTime())
	require.Equal(t, 120*time.Minute.Milliseconds(), db.Blocks()[0].MaxTime())

	// Checking that ooo chunk is empty in Head.
	for _, lbls := range []labels.Labels{series1, series2} {
		ms, created, err := db.head.getOrCreate(lbls.Hash(), lbls)
		require.NoError(t, err)
		require.False(t, created)
		require.Nil(t, ms.ooo)
	}

	verifySamples(90, 109)
}

func Test_Querier_OOOQuery(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 24 * time.Hour.Milliseconds()

	series1 := labels.FromStrings("foo", "bar1")

	minutes := func(m int64) int64 { return m * time.Minute.Milliseconds() }
	addSample := func(db *DB, fromMins, toMins, queryMinT, queryMaxT int64, expSamples []chunks.Sample) ([]chunks.Sample, int) {
		app := db.Appender(context.Background())
		totalAppended := 0
		for min := fromMins; min <= toMins; min += time.Minute.Milliseconds() {
			_, err := app.Append(0, series1, min, float64(min))
			if min >= queryMinT && min <= queryMaxT {
				expSamples = append(expSamples, sample{t: min, f: float64(min)})
			}
			require.NoError(t, err)
			totalAppended++
		}
		require.NoError(t, app.Commit())
		return expSamples, totalAppended
	}

	tests := []struct {
		name        string
		queryMinT   int64
		queryMaxT   int64
		inOrderMinT int64
		inOrderMaxT int64
		oooMinT     int64
		oooMaxT     int64
	}{
		{
			name:        "query interval covering ooomint and inordermaxt returns all ingested samples",
			queryMinT:   minutes(0),
			queryMaxT:   minutes(200),
			inOrderMinT: minutes(100),
			inOrderMaxT: minutes(200),
			oooMinT:     minutes(0),
			oooMaxT:     minutes(99),
		},
		{
			name:        "partial query interval returns only samples within interval",
			queryMinT:   minutes(20),
			queryMaxT:   minutes(180),
			inOrderMinT: minutes(100),
			inOrderMaxT: minutes(200),
			oooMinT:     minutes(0),
			oooMaxT:     minutes(99),
		},
	}
	for _, tc := range tests {
		t.Run(fmt.Sprintf("name=%s", tc.name), func(t *testing.T) {
			db := openTestDB(t, opts, nil)
			db.DisableCompactions()
			defer func() {
				require.NoError(t, db.Close())
			}()

			var expSamples []chunks.Sample

			// Add in-order samples.
			expSamples, _ = addSample(db, tc.inOrderMinT, tc.inOrderMaxT, tc.queryMinT, tc.queryMaxT, expSamples)

			// Add out-of-order samples.
			expSamples, oooSamples := addSample(db, tc.oooMinT, tc.oooMaxT, tc.queryMinT, tc.queryMaxT, expSamples)

			sort.Slice(expSamples, func(i, j int) bool {
				return expSamples[i].T() < expSamples[j].T()
			})

			querier, err := db.Querier(tc.queryMinT, tc.queryMaxT)
			require.NoError(t, err)
			defer querier.Close()

			seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar1"))
			require.NotNil(t, seriesSet[series1.String()])
			require.Len(t, seriesSet, 1)
			require.Equal(t, expSamples, seriesSet[series1.String()])
			requireEqualOOOSamples(t, oooSamples, db)
		})
	}
}

func Test_ChunkQuerier_OOOQuery(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 24 * time.Hour.Milliseconds()

	series1 := labels.FromStrings("foo", "bar1")

	minutes := func(m int64) int64 { return m * time.Minute.Milliseconds() }
	addSample := func(db *DB, fromMins, toMins, queryMinT, queryMaxT int64, expSamples []chunks.Sample) ([]chunks.Sample, int) {
		app := db.Appender(context.Background())
		totalAppended := 0
		for min := fromMins; min <= toMins; min += time.Minute.Milliseconds() {
			_, err := app.Append(0, series1, min, float64(min))
			if min >= queryMinT && min <= queryMaxT {
				expSamples = append(expSamples, sample{t: min, f: float64(min)})
			}
			require.NoError(t, err)
			totalAppended++
		}
		require.NoError(t, app.Commit())
		return expSamples, totalAppended
	}

	tests := []struct {
		name        string
		queryMinT   int64
		queryMaxT   int64
		inOrderMinT int64
		inOrderMaxT int64
		oooMinT     int64
		oooMaxT     int64
	}{
		{
			name:        "query interval covering ooomint and inordermaxt returns all ingested samples",
			queryMinT:   minutes(0),
			queryMaxT:   minutes(200),
			inOrderMinT: minutes(100),
			inOrderMaxT: minutes(200),
			oooMinT:     minutes(0),
			oooMaxT:     minutes(99),
		},
		{
			name:        "partial query interval returns only samples within interval",
			queryMinT:   minutes(20),
			queryMaxT:   minutes(180),
			inOrderMinT: minutes(100),
			inOrderMaxT: minutes(200),
			oooMinT:     minutes(0),
			oooMaxT:     minutes(99),
		},
	}
	for _, tc := range tests {
		t.Run(fmt.Sprintf("name=%s", tc.name), func(t *testing.T) {
			db := openTestDB(t, opts, nil)
			db.DisableCompactions()
			defer func() {
				require.NoError(t, db.Close())
			}()

			var expSamples []chunks.Sample

			// Add in-order samples.
			expSamples, _ = addSample(db, tc.inOrderMinT, tc.inOrderMaxT, tc.queryMinT, tc.queryMaxT, expSamples)

			// Add out-of-order samples.
			expSamples, oooSamples := addSample(db, tc.oooMinT, tc.oooMaxT, tc.queryMinT, tc.queryMaxT, expSamples)

			sort.Slice(expSamples, func(i, j int) bool {
				return expSamples[i].T() < expSamples[j].T()
			})

			querier, err := db.ChunkQuerier(tc.queryMinT, tc.queryMaxT)
			require.NoError(t, err)
			defer querier.Close()

			chks := queryChunks(t, querier, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar1"))
			require.NotNil(t, chks[series1.String()])
			require.Len(t, chks, 1)
			requireEqualOOOSamples(t, oooSamples, db)
			var gotSamples []chunks.Sample
			for _, chunk := range chks[series1.String()] {
				it := chunk.Chunk.Iterator(nil)
				for it.Next() == chunkenc.ValFloat {
					ts, v := it.At()
					gotSamples = append(gotSamples, sample{t: ts, f: v})
				}
			}
			require.Equal(t, expSamples, gotSamples)
		})
	}
}

func TestOOOAppendAndQuery(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 4 * time.Hour.Milliseconds()

	db := openTestDB(t, opts, nil)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	s1 := labels.FromStrings("foo", "bar1")
	s2 := labels.FromStrings("foo", "bar2")

	minutes := func(m int64) int64 { return m * time.Minute.Milliseconds() }
	appendedSamples := make(map[string][]chunks.Sample)
	totalSamples := 0
	addSample := func(lbls labels.Labels, fromMins, toMins int64, faceError bool) {
		app := db.Appender(context.Background())
		key := lbls.String()
		from, to := minutes(fromMins), minutes(toMins)
		for min := from; min <= to; min += time.Minute.Milliseconds() {
			val := rand.Float64()
			_, err := app.Append(0, lbls, min, val)
			if faceError {
				require.Error(t, err)
			} else {
				require.NoError(t, err)
				appendedSamples[key] = append(appendedSamples[key], sample{t: min, f: val})
				totalSamples++
			}
		}
		if faceError {
			require.NoError(t, app.Rollback())
		} else {
			require.NoError(t, app.Commit())
		}
	}

	testQuery := func(from, to int64) {
		querier, err := db.Querier(from, to)
		require.NoError(t, err)

		seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar."))

		for k, v := range appendedSamples {
			sort.Slice(v, func(i, j int) bool {
				return v[i].T() < v[j].T()
			})
			appendedSamples[k] = v
		}

		expSamples := make(map[string][]chunks.Sample)
		for k, samples := range appendedSamples {
			for _, s := range samples {
				if s.T() < from {
					continue
				}
				if s.T() > to {
					continue
				}
				expSamples[k] = append(expSamples[k], s)
			}
		}
		require.Equal(t, expSamples, seriesSet)
		requireEqualOOOSamples(t, totalSamples-2, db)
	}

	verifyOOOMinMaxTimes := func(expMin, expMax int64) {
		require.Equal(t, minutes(expMin), db.head.MinOOOTime())
		require.Equal(t, minutes(expMax), db.head.MaxOOOTime())
	}

	// In-order samples.
	addSample(s1, 300, 300, false)
	addSample(s2, 290, 290, false)
	require.Equal(t, float64(2), prom_testutil.ToFloat64(db.head.metrics.chunksCreated))
	testQuery(math.MinInt64, math.MaxInt64)

	// Some ooo samples.
	addSample(s1, 250, 260, false)
	addSample(s2, 255, 265, false)
	verifyOOOMinMaxTimes(250, 265)
	testQuery(math.MinInt64, math.MaxInt64)
	testQuery(minutes(250), minutes(265)) // Test querying ono data time range
	testQuery(minutes(290), minutes(300)) // Test querying in-order data time range
	testQuery(minutes(250), minutes(300)) // Test querying the entire range

	// Out of time window.
	addSample(s1, 59, 59, true)
	addSample(s2, 49, 49, true)
	verifyOOOMinMaxTimes(250, 265)
	testQuery(math.MinInt64, math.MaxInt64)

	// At the edge of time window, also it would be "out of bound" without the ooo support.
	addSample(s1, 60, 65, false)
	verifyOOOMinMaxTimes(60, 265)
	testQuery(math.MinInt64, math.MaxInt64)

	// This sample is not within the time window w.r.t. the head's maxt, but it is within the window
	// w.r.t. the series' maxt. But we consider only head's maxt.
	addSample(s2, 59, 59, true)
	verifyOOOMinMaxTimes(60, 265)
	testQuery(math.MinInt64, math.MaxInt64)

	// Now the sample is within time window w.r.t. the head's maxt.
	addSample(s2, 60, 65, false)
	verifyOOOMinMaxTimes(60, 265)
	testQuery(math.MinInt64, math.MaxInt64)

	// Out of time window again.
	addSample(s1, 59, 59, true)
	addSample(s2, 49, 49, true)
	testQuery(math.MinInt64, math.MaxInt64)

	// Generating some m-map chunks. The m-map chunks here are in such a way
	// that when sorted w.r.t. mint, the last chunk's maxt is not the overall maxt
	// of the merged chunk. This tests a bug fixed in https://github.com/grafana/mimir-prometheus/pull/238/.
	require.Equal(t, float64(4), prom_testutil.ToFloat64(db.head.metrics.chunksCreated))
	addSample(s1, 180, 249, false)
	require.Equal(t, float64(6), prom_testutil.ToFloat64(db.head.metrics.chunksCreated))
	verifyOOOMinMaxTimes(60, 265)
	testQuery(math.MinInt64, math.MaxInt64)
}

func TestOOODisabled(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 0
	db := openTestDB(t, opts, nil)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	s1 := labels.FromStrings("foo", "bar1")
	minutes := func(m int64) int64 { return m * time.Minute.Milliseconds() }
	expSamples := make(map[string][]chunks.Sample)
	totalSamples := 0
	failedSamples := 0
	addSample := func(lbls labels.Labels, fromMins, toMins int64, faceError bool) {
		app := db.Appender(context.Background())
		key := lbls.String()
		from, to := minutes(fromMins), minutes(toMins)
		for min := from; min <= to; min += time.Minute.Milliseconds() {
			val := rand.Float64()
			_, err := app.Append(0, lbls, min, val)
			if faceError {
				require.Error(t, err)
				failedSamples++
			} else {
				require.NoError(t, err)
				expSamples[key] = append(expSamples[key], sample{t: min, f: val})
				totalSamples++
			}
		}
		if faceError {
			require.NoError(t, app.Rollback())
		} else {
			require.NoError(t, app.Commit())
		}
	}

	addSample(s1, 300, 300, false) // In-order samples.
	addSample(s1, 250, 260, true)  // Some ooo samples.
	addSample(s1, 59, 59, true)    // Out of time window.
	addSample(s1, 60, 65, true)    // At the edge of time window, also it would be "out of bound" without the ooo support.
	addSample(s1, 59, 59, true)    // Out of time window again.
	addSample(s1, 301, 310, false) // More in-order samples.

	querier, err := db.Querier(math.MinInt64, math.MaxInt64)
	require.NoError(t, err)

	seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar."))
	require.Equal(t, expSamples, seriesSet)
	requireEqualOOOSamples(t, 0, db)
	require.Equal(t, float64(failedSamples),
		prom_testutil.ToFloat64(db.head.metrics.outOfOrderSamples.WithLabelValues(sampleMetricTypeFloat))+prom_testutil.ToFloat64(db.head.metrics.outOfBoundSamples.WithLabelValues(sampleMetricTypeFloat)),
		"number of ooo/oob samples mismatch")

	// Verifying that no OOO artifacts were generated.
	_, err = os.ReadDir(path.Join(db.Dir(), wlog.WblDirName))
	require.True(t, os.IsNotExist(err))

	ms, created, err := db.head.getOrCreate(s1.Hash(), s1)
	require.NoError(t, err)
	require.False(t, created)
	require.NotNil(t, ms)
	require.Nil(t, ms.ooo)
}

func TestWBLAndMmapReplay(t *testing.T) {
	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 4 * time.Hour.Milliseconds()

	db := openTestDB(t, opts, nil)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	s1 := labels.FromStrings("foo", "bar1")

	minutes := func(m int64) int64 { return m * time.Minute.Milliseconds() }
	expSamples := make(map[string][]chunks.Sample)
	totalSamples := 0
	addSample := func(lbls labels.Labels, fromMins, toMins int64) {
		app := db.Appender(context.Background())
		key := lbls.String()
		from, to := minutes(fromMins), minutes(toMins)
		for min := from; min <= to; min += time.Minute.Milliseconds() {
			val := rand.Float64()
			_, err := app.Append(0, lbls, min, val)
			require.NoError(t, err)
			expSamples[key] = append(expSamples[key], sample{t: min, f: val})
			totalSamples++
		}
		require.NoError(t, app.Commit())
	}

	testQuery := func(exp map[string][]chunks.Sample) {
		querier, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		seriesSet := query(t, querier, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar."))

		for k, v := range exp {
			sort.Slice(v, func(i, j int) bool {
				return v[i].T() < v[j].T()
			})
			exp[k] = v
		}
		require.Equal(t, exp, seriesSet)
	}

	// In-order samples.
	addSample(s1, 300, 300)
	require.Equal(t, float64(1), prom_testutil.ToFloat64(db.head.metrics.chunksCreated))

	// Some ooo samples.
	addSample(s1, 250, 260)
	addSample(s1, 195, 249) // This creates some m-map chunks.
	require.Equal(t, float64(4), prom_testutil.ToFloat64(db.head.metrics.chunksCreated))
	testQuery(expSamples)
	oooMint, oooMaxt := minutes(195), minutes(260)

	// Collect the samples only present in the ooo m-map chunks.
	ms, created, err := db.head.getOrCreate(s1.Hash(), s1)
	require.False(t, created)
	require.NoError(t, err)
	var s1MmapSamples []chunks.Sample
	for _, mc := range ms.ooo.oooMmappedChunks {
		chk, err := db.head.chunkDiskMapper.Chunk(mc.ref)
		require.NoError(t, err)
		it := chk.Iterator(nil)
		for it.Next() == chunkenc.ValFloat {
			ts, val := it.At()
			s1MmapSamples = append(s1MmapSamples, sample{t: ts, f: val})
		}
	}
	require.NotEmpty(t, s1MmapSamples)

	require.NoError(t, db.Close())

	// Making a copy of original state of WBL and Mmap files to use it later.
	mmapDir := mmappedChunksDir(db.head.opts.ChunkDirRoot)
	wblDir := db.head.wbl.Dir()
	originalWblDir := filepath.Join(t.TempDir(), "original_wbl")
	originalMmapDir := filepath.Join(t.TempDir(), "original_mmap")
	require.NoError(t, fileutil.CopyDirs(wblDir, originalWblDir))
	require.NoError(t, fileutil.CopyDirs(mmapDir, originalMmapDir))
	resetWBLToOriginal := func() {
		require.NoError(t, os.RemoveAll(wblDir))
		require.NoError(t, fileutil.CopyDirs(originalWblDir, wblDir))
	}
	resetMmapToOriginal := func() {
		require.NoError(t, os.RemoveAll(mmapDir))
		require.NoError(t, fileutil.CopyDirs(originalMmapDir, mmapDir))
	}

	t.Run("Restart DB with both WBL and M-map files for ooo data", func(t *testing.T) {
		db, err = Open(db.dir, nil, nil, opts, nil)
		require.NoError(t, err)
		require.Equal(t, oooMint, db.head.MinOOOTime())
		require.Equal(t, oooMaxt, db.head.MaxOOOTime())
		testQuery(expSamples)
		require.NoError(t, db.Close())
	})

	t.Run("Restart DB with only WBL for ooo data", func(t *testing.T) {
		require.NoError(t, os.RemoveAll(mmapDir))

		db, err = Open(db.dir, nil, nil, opts, nil)
		require.NoError(t, err)
		require.Equal(t, oooMint, db.head.MinOOOTime())
		require.Equal(t, oooMaxt, db.head.MaxOOOTime())
		testQuery(expSamples)
		require.NoError(t, db.Close())
	})

	t.Run("Restart DB with only M-map files for ooo data", func(t *testing.T) {
		require.NoError(t, os.RemoveAll(wblDir))
		resetMmapToOriginal()

		db, err = Open(db.dir, nil, nil, opts, nil)
		require.NoError(t, err)
		require.Equal(t, oooMint, db.head.MinOOOTime())
		require.Equal(t, oooMaxt, db.head.MaxOOOTime())
		inOrderSample := expSamples[s1.String()][len(expSamples[s1.String()])-1]
		testQuery(map[string][]chunks.Sample{
			s1.String(): append(s1MmapSamples, inOrderSample),
		})
		require.NoError(t, db.Close())
	})

	t.Run("Restart DB with WBL+Mmap while increasing the OOOCapMax", func(t *testing.T) {
		resetWBLToOriginal()
		resetMmapToOriginal()

		opts.OutOfOrderCapMax = 60
		db, err = Open(db.dir, nil, nil, opts, nil)
		require.NoError(t, err)
		require.Equal(t, oooMint, db.head.MinOOOTime())
		require.Equal(t, oooMaxt, db.head.MaxOOOTime())
		testQuery(expSamples)
		require.NoError(t, db.Close())
	})

	t.Run("Restart DB with WBL+Mmap while decreasing the OOOCapMax", func(t *testing.T) {
		resetMmapToOriginal() // We need to reset because new duplicate chunks can be written above.

		opts.OutOfOrderCapMax = 10
		db, err = Open(db.dir, nil, nil, opts, nil)
		require.NoError(t, err)
		require.Equal(t, oooMint, db.head.MinOOOTime())
		require.Equal(t, oooMaxt, db.head.MaxOOOTime())
		testQuery(expSamples)
		require.NoError(t, db.Close())
	})

	t.Run("Restart DB with WBL+Mmap while having no m-map markers in WBL", func(t *testing.T) {
		resetMmapToOriginal() // We neet to reset because new duplicate chunks can be written above.

		// Removing m-map markers in WBL by rewriting it.
		newWbl, err := wlog.New(log.NewNopLogger(), nil, filepath.Join(t.TempDir(), "new_wbl"), wlog.CompressionNone)
		require.NoError(t, err)
		sr, err := wlog.NewSegmentsReader(originalWblDir)
		require.NoError(t, err)
		dec := record.NewDecoder(labels.NewSymbolTable())
		r, markers, addedRecs := wlog.NewReader(sr), 0, 0
		for r.Next() {
			rec := r.Record()
			if dec.Type(rec) == record.MmapMarkers {
				markers++
				continue
			}
			addedRecs++
			require.NoError(t, newWbl.Log(rec))
		}
		require.Greater(t, markers, 0)
		require.Greater(t, addedRecs, 0)
		require.NoError(t, newWbl.Close())
		require.NoError(t, sr.Close())
		require.NoError(t, os.RemoveAll(wblDir))
		require.NoError(t, os.Rename(newWbl.Dir(), wblDir))

		opts.OutOfOrderCapMax = 30
		db, err = Open(db.dir, nil, nil, opts, nil)
		require.NoError(t, err)
		require.Equal(t, oooMint, db.head.MinOOOTime())
		require.Equal(t, oooMaxt, db.head.MaxOOOTime())
		testQuery(expSamples)
	})
}

func TestOOOCompactionFailure(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions() // We want to manually call it.
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")

	addSample := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSample(250, 350)

	// Add ooo samples that creates multiple chunks.
	addSample(90, 310)

	// No blocks before compaction.
	require.Empty(t, db.Blocks())

	// There is a 0th WBL file.
	verifyFirstWBLFileIs0 := func(count int) {
		require.NoError(t, db.head.wbl.Sync()) // syncing to make sure wbl is flushed in windows
		files, err := os.ReadDir(db.head.wbl.Dir())
		require.NoError(t, err)
		require.Len(t, files, count)
		require.Equal(t, "00000000", files[0].Name())
		f, err := files[0].Info()
		require.NoError(t, err)
		require.Greater(t, f.Size(), int64(100))
	}
	verifyFirstWBLFileIs0(1)

	verifyMmapFiles := func(exp ...string) {
		mmapDir := mmappedChunksDir(db.head.opts.ChunkDirRoot)
		files, err := os.ReadDir(mmapDir)
		require.NoError(t, err)
		require.Len(t, files, len(exp))
		for i, f := range files {
			require.Equal(t, exp[i], f.Name())
		}
	}

	verifyMmapFiles("000001")

	// OOO compaction fails 5 times.
	originalCompactor := db.compactor
	db.compactor = &mockCompactorFailing{t: t}
	for i := 0; i < 5; i++ {
		require.Error(t, db.CompactOOOHead(ctx))
	}
	require.Empty(t, db.Blocks())

	// M-map files don't change after failed compaction.
	verifyMmapFiles("000001")

	// Because of 5 compaction attempts, there are 6 files now.
	verifyFirstWBLFileIs0(6)

	db.compactor = originalCompactor
	require.NoError(t, db.CompactOOOHead(ctx))
	oldBlocks := db.Blocks()
	require.Len(t, db.Blocks(), 3)

	// Check that the ooo chunks were removed.
	ms, created, err := db.head.getOrCreate(series1.Hash(), series1)
	require.NoError(t, err)
	require.False(t, created)
	require.Nil(t, ms.ooo)

	// The failed compaction should not have left the ooo Head corrupted.
	// Hence, expect no new blocks with another OOO compaction call.
	require.NoError(t, db.CompactOOOHead(ctx))
	require.Len(t, db.Blocks(), 3)
	require.Equal(t, oldBlocks, db.Blocks())

	// There should be a single m-map file
	verifyMmapFiles("000001")

	// All but last WBL file will be deleted.
	// 8 files in total (starting at 0) because of 7 compaction calls.
	files, err := os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 1)
	require.Equal(t, "00000007", files[0].Name())
	f, err := files[0].Info()
	require.NoError(t, err)
	require.Equal(t, int64(0), f.Size())

	verifySamples := func(block *Block, fromMins, toMins int64) {
		series1Samples := make([]chunks.Sample, 0, toMins-fromMins+1)
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			series1Samples = append(series1Samples, sample{ts, float64(ts), nil, nil})
		}
		expRes := map[string][]chunks.Sample{
			series1.String(): series1Samples,
		}

		q, err := NewBlockQuerier(block, math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	// Checking for expected data in the blocks.
	verifySamples(db.Blocks()[0], 90, 119)
	verifySamples(db.Blocks()[1], 120, 239)
	verifySamples(db.Blocks()[2], 240, 310)

	// Compact the in-order head and expect another block.
	// Since this is a forced compaction, this block is not aligned with 2h.
	err = db.CompactHead(NewRangeHead(db.head, 250*time.Minute.Milliseconds(), 350*time.Minute.Milliseconds()))
	require.NoError(t, err)
	require.Len(t, db.Blocks(), 4) // [0, 120), [120, 240), [240, 360), [250, 351)
	verifySamples(db.Blocks()[3], 250, 350)

	// The compaction also clears out the old m-map files. Including
	// the file that has ooo chunks.
	verifyMmapFiles("000001")
}

func TestWBLCorruption(t *testing.T) {
	dir := t.TempDir()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 30
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	var allSamples, expAfterRestart []chunks.Sample
	addSamples := func(fromMins, toMins int64, afterRestart bool) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			allSamples = append(allSamples, sample{t: ts, f: float64(ts)})
			if afterRestart {
				expAfterRestart = append(expAfterRestart, sample{t: ts, f: float64(ts)})
			}
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSamples(340, 350, true)

	// OOO samples.
	addSamples(90, 99, true)
	addSamples(100, 119, true)
	addSamples(120, 130, true)

	// Moving onto the second file.
	_, err = db.head.wbl.NextSegment()
	require.NoError(t, err)

	// More OOO samples.
	addSamples(200, 230, true)
	addSamples(240, 255, true)

	// We corrupt WBL after the sample at 255. So everything added later
	// should be deleted after replay.

	// Checking where we corrupt it.
	require.NoError(t, db.head.wbl.Sync()) // syncing to make sure wbl is flushed in windows
	files, err := os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 2)
	f1, err := files[1].Info()
	require.NoError(t, err)
	corruptIndex := f1.Size()
	corruptFilePath := path.Join(db.head.wbl.Dir(), files[1].Name())

	// Corrupt the WBL by adding a malformed record.
	require.NoError(t, db.head.wbl.Log([]byte{byte(record.Samples), 99, 9, 99, 9, 99, 9, 99}))

	// More samples after the corruption point.
	addSamples(260, 280, false)
	addSamples(290, 300, false)

	// Another file.
	_, err = db.head.wbl.NextSegment()
	require.NoError(t, err)

	addSamples(310, 320, false)

	// Verifying that we have data after corruption point.
	require.NoError(t, db.head.wbl.Sync()) // syncing to make sure wbl is flushed in windows
	files, err = os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 3)
	f1, err = files[1].Info()
	require.NoError(t, err)
	require.Greater(t, f1.Size(), corruptIndex)
	f0, err := files[0].Info()
	require.NoError(t, err)
	require.Greater(t, f0.Size(), int64(100))
	f2, err := files[2].Info()
	require.NoError(t, err)
	require.Greater(t, f2.Size(), int64(100))

	verifySamples := func(expSamples []chunks.Sample) {
		sort.Slice(expSamples, func(i, j int) bool {
			return expSamples[i].T() < expSamples[j].T()
		})

		expRes := map[string][]chunks.Sample{
			series1.String(): expSamples,
		}

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	verifySamples(allSamples)

	require.NoError(t, db.Close())

	// We want everything to be replayed from the WBL. So we delete the m-map files.
	require.NoError(t, os.RemoveAll(mmappedChunksDir(db.head.opts.ChunkDirRoot)))

	// Restart does the replay and repair.
	db, err = Open(db.dir, nil, nil, opts, nil)
	require.NoError(t, err)
	require.Equal(t, 1.0, prom_testutil.ToFloat64(db.head.metrics.walCorruptionsTotal))
	require.Less(t, len(expAfterRestart), len(allSamples))
	verifySamples(expAfterRestart)

	// Verify that it did the repair on disk.
	files, err = os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 3)
	f0, err = files[0].Info()
	require.NoError(t, err)
	require.Greater(t, f0.Size(), int64(100))
	f2, err = files[2].Info()
	require.NoError(t, err)
	require.Equal(t, int64(0), f2.Size())
	require.Equal(t, corruptFilePath, path.Join(db.head.wbl.Dir(), files[1].Name()))

	// Verifying that everything after the corruption point is set to 0.
	b, err := os.ReadFile(corruptFilePath)
	require.NoError(t, err)
	sum := 0
	for _, val := range b[corruptIndex:] {
		sum += int(val)
	}
	require.Equal(t, 0, sum)

	// Another restart, everything normal with no repair.
	require.NoError(t, db.Close())
	db, err = Open(db.dir, nil, nil, opts, nil)
	require.NoError(t, err)
	require.Equal(t, 0.0, prom_testutil.ToFloat64(db.head.metrics.walCorruptionsTotal))
	verifySamples(expAfterRestart)
}

func TestOOOMmapCorruption(t *testing.T) {
	dir := t.TempDir()

	opts := DefaultOptions()
	opts.OutOfOrderCapMax = 10
	opts.OutOfOrderTimeWindow = 300 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	var allSamples, expInMmapChunks []chunks.Sample
	addSamples := func(fromMins, toMins int64, inMmapAfterCorruption bool) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			allSamples = append(allSamples, sample{t: ts, f: float64(ts)})
			if inMmapAfterCorruption {
				expInMmapChunks = append(expInMmapChunks, sample{t: ts, f: float64(ts)})
			}
		}
		require.NoError(t, app.Commit())
	}

	// Add an in-order samples.
	addSamples(340, 350, true)

	// OOO samples.
	addSamples(90, 99, true)
	addSamples(100, 109, true)
	// This sample m-maps a chunk. But 120 goes into a new chunk.
	addSamples(120, 120, false)

	// Second m-map file. We will corrupt this file. Sample 120 goes into this new file.
	db.head.chunkDiskMapper.CutNewFile()

	// More OOO samples.
	addSamples(200, 230, false)
	addSamples(240, 255, false)

	db.head.chunkDiskMapper.CutNewFile()
	addSamples(260, 290, false)

	verifySamples := func(expSamples []chunks.Sample) {
		sort.Slice(expSamples, func(i, j int) bool {
			return expSamples[i].T() < expSamples[j].T()
		})

		expRes := map[string][]chunks.Sample{
			series1.String(): expSamples,
		}

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	verifySamples(allSamples)

	// Verifying existing files.
	mmapDir := mmappedChunksDir(db.head.opts.ChunkDirRoot)
	files, err := os.ReadDir(mmapDir)
	require.NoError(t, err)
	require.Len(t, files, 3)

	// Corrupting the 2nd file.
	f, err := os.OpenFile(path.Join(mmapDir, files[1].Name()), os.O_RDWR, 0o666)
	require.NoError(t, err)
	_, err = f.WriteAt([]byte{99, 9, 99, 9, 99}, 20)
	require.NoError(t, err)
	require.NoError(t, f.Close())
	firstFileName := files[0].Name()

	require.NoError(t, db.Close())

	// Moving OOO WBL to use it later.
	wblDir := db.head.wbl.Dir()
	wblDirTmp := path.Join(t.TempDir(), "wbl_tmp")
	require.NoError(t, os.Rename(wblDir, wblDirTmp))

	// Restart does the replay and repair of m-map files.
	db, err = Open(db.dir, nil, nil, opts, nil)
	require.NoError(t, err)
	require.Equal(t, 1.0, prom_testutil.ToFloat64(db.head.metrics.mmapChunkCorruptionTotal))
	require.Less(t, len(expInMmapChunks), len(allSamples))

	// Since there is no WBL, only samples from m-map chunks comes in the query.
	verifySamples(expInMmapChunks)

	// Verify that it did the repair on disk. All files from the point of corruption
	// should be deleted.
	files, err = os.ReadDir(mmapDir)
	require.NoError(t, err)
	require.Len(t, files, 1)
	f0, err := files[0].Info()
	require.NoError(t, err)
	require.Greater(t, f0.Size(), int64(100))
	require.Equal(t, firstFileName, files[0].Name())

	// Another restart, everything normal with no repair.
	require.NoError(t, db.Close())
	db, err = Open(db.dir, nil, nil, opts, nil)
	require.NoError(t, err)
	require.Equal(t, 0.0, prom_testutil.ToFloat64(db.head.metrics.mmapChunkCorruptionTotal))
	verifySamples(expInMmapChunks)

	// Restart again with the WBL, all samples should be present now.
	require.NoError(t, db.Close())
	require.NoError(t, os.RemoveAll(wblDir))
	require.NoError(t, os.Rename(wblDirTmp, wblDir))
	db, err = Open(db.dir, nil, nil, opts, nil)
	require.NoError(t, err)
	verifySamples(allSamples)
}

func TestOutOfOrderRuntimeConfig(t *testing.T) {
	ctx := context.Background()

	getDB := func(oooTimeWindow int64) *DB {
		dir := t.TempDir()

		opts := DefaultOptions()
		opts.OutOfOrderTimeWindow = oooTimeWindow

		db, err := Open(dir, nil, nil, opts, nil)
		require.NoError(t, err)
		db.DisableCompactions()
		t.Cleanup(func() {
			require.NoError(t, db.Close())
		})

		return db
	}

	makeConfig := func(oooTimeWindow int) *config.Config {
		return &config.Config{
			StorageConfig: config.StorageConfig{
				TSDBConfig: &config.TSDBConfig{
					OutOfOrderTimeWindow: int64(oooTimeWindow) * time.Minute.Milliseconds(),
				},
			},
		}
	}

	series1 := labels.FromStrings("foo", "bar1")
	addSamples := func(t *testing.T, db *DB, fromMins, toMins int64, success bool, allSamples []chunks.Sample) []chunks.Sample {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			if success {
				require.NoError(t, err)
				allSamples = append(allSamples, sample{t: ts, f: float64(ts)})
			} else {
				require.Error(t, err)
			}
		}
		require.NoError(t, app.Commit())
		return allSamples
	}

	verifySamples := func(t *testing.T, db *DB, expSamples []chunks.Sample) {
		sort.Slice(expSamples, func(i, j int) bool {
			return expSamples[i].T() < expSamples[j].T()
		})

		expRes := map[string][]chunks.Sample{
			series1.String(): expSamples,
		}

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	doOOOCompaction := func(t *testing.T, db *DB) {
		// WBL is not empty.
		size, err := db.head.wbl.Size()
		require.NoError(t, err)
		require.Greater(t, size, int64(0))

		require.Empty(t, db.Blocks())
		require.NoError(t, db.compactOOOHead(ctx))
		require.NotEmpty(t, db.Blocks())

		// WBL is empty.
		size, err = db.head.wbl.Size()
		require.NoError(t, err)
		require.Equal(t, int64(0), size)
	}

	t.Run("increase time window", func(t *testing.T) {
		var allSamples []chunks.Sample
		db := getDB(30 * time.Minute.Milliseconds())

		// In-order.
		allSamples = addSamples(t, db, 300, 310, true, allSamples)

		// OOO upto 30m old is success.
		allSamples = addSamples(t, db, 281, 290, true, allSamples)

		// OOO of 59m old fails.
		s := addSamples(t, db, 251, 260, false, nil)
		require.Empty(t, s)
		verifySamples(t, db, allSamples)

		oldWblPtr := fmt.Sprintf("%p", db.head.wbl)

		// Increase time window and try adding again.
		err := db.ApplyConfig(makeConfig(60))
		require.NoError(t, err)
		allSamples = addSamples(t, db, 251, 260, true, allSamples)

		// WBL does not change.
		newWblPtr := fmt.Sprintf("%p", db.head.wbl)
		require.Equal(t, oldWblPtr, newWblPtr)

		doOOOCompaction(t, db)
		verifySamples(t, db, allSamples)
	})

	t.Run("decrease time window and increase again", func(t *testing.T) {
		var allSamples []chunks.Sample
		db := getDB(60 * time.Minute.Milliseconds())

		// In-order.
		allSamples = addSamples(t, db, 300, 310, true, allSamples)

		// OOO upto 59m old is success.
		allSamples = addSamples(t, db, 251, 260, true, allSamples)

		oldWblPtr := fmt.Sprintf("%p", db.head.wbl)
		// Decrease time window.
		err := db.ApplyConfig(makeConfig(30))
		require.NoError(t, err)

		// OOO of 49m old fails.
		s := addSamples(t, db, 261, 270, false, nil)
		require.Empty(t, s)

		// WBL does not change.
		newWblPtr := fmt.Sprintf("%p", db.head.wbl)
		require.Equal(t, oldWblPtr, newWblPtr)

		verifySamples(t, db, allSamples)

		// Increase time window again and check
		err = db.ApplyConfig(makeConfig(60))
		require.NoError(t, err)
		allSamples = addSamples(t, db, 261, 270, true, allSamples)
		verifySamples(t, db, allSamples)

		// WBL does not change.
		newWblPtr = fmt.Sprintf("%p", db.head.wbl)
		require.Equal(t, oldWblPtr, newWblPtr)

		doOOOCompaction(t, db)
		verifySamples(t, db, allSamples)
	})

	t.Run("disabled to enabled", func(t *testing.T) {
		var allSamples []chunks.Sample
		db := getDB(0)

		// In-order.
		allSamples = addSamples(t, db, 300, 310, true, allSamples)

		// OOO fails.
		s := addSamples(t, db, 251, 260, false, nil)
		require.Empty(t, s)
		verifySamples(t, db, allSamples)

		require.Nil(t, db.head.wbl)

		// Increase time window and try adding again.
		err := db.ApplyConfig(makeConfig(60))
		require.NoError(t, err)
		allSamples = addSamples(t, db, 251, 260, true, allSamples)

		// WBL gets created.
		require.NotNil(t, db.head.wbl)

		verifySamples(t, db, allSamples)

		// OOO compaction works now.
		doOOOCompaction(t, db)
		verifySamples(t, db, allSamples)
	})

	t.Run("enabled to disabled", func(t *testing.T) {
		var allSamples []chunks.Sample
		db := getDB(60 * time.Minute.Milliseconds())

		// In-order.
		allSamples = addSamples(t, db, 300, 310, true, allSamples)

		// OOO upto 59m old is success.
		allSamples = addSamples(t, db, 251, 260, true, allSamples)

		oldWblPtr := fmt.Sprintf("%p", db.head.wbl)
		// Time Window to 0, hence disabled.
		err := db.ApplyConfig(makeConfig(0))
		require.NoError(t, err)

		// OOO within old time window fails.
		s := addSamples(t, db, 290, 309, false, nil)
		require.Empty(t, s)

		// WBL does not change and is not removed.
		newWblPtr := fmt.Sprintf("%p", db.head.wbl)
		require.Equal(t, oldWblPtr, newWblPtr)

		verifySamples(t, db, allSamples)

		// Compaction still works after disabling with WBL cleanup.
		doOOOCompaction(t, db)
		verifySamples(t, db, allSamples)
	})

	t.Run("disabled to disabled", func(t *testing.T) {
		var allSamples []chunks.Sample
		db := getDB(0)

		// In-order.
		allSamples = addSamples(t, db, 300, 310, true, allSamples)

		// OOO fails.
		s := addSamples(t, db, 290, 309, false, nil)
		require.Empty(t, s)
		verifySamples(t, db, allSamples)
		require.Nil(t, db.head.wbl)

		// Time window to 0.
		err := db.ApplyConfig(makeConfig(0))
		require.NoError(t, err)

		// OOO still fails.
		s = addSamples(t, db, 290, 309, false, nil)
		require.Empty(t, s)
		verifySamples(t, db, allSamples)
		require.Nil(t, db.head.wbl)
	})
}

func TestNoGapAfterRestartWithOOO(t *testing.T) {
	series1 := labels.FromStrings("foo", "bar1")
	addSamples := func(t *testing.T, db *DB, fromMins, toMins int64, success bool) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			if success {
				require.NoError(t, err)
			} else {
				require.Error(t, err)
			}
		}
		require.NoError(t, app.Commit())
	}

	verifySamples := func(t *testing.T, db *DB, fromMins, toMins int64) {
		var expSamples []chunks.Sample
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			expSamples = append(expSamples, sample{t: ts, f: float64(ts)})
		}

		expRes := map[string][]chunks.Sample{
			series1.String(): expSamples,
		}

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	cases := []struct {
		inOrderMint, inOrderMaxt int64
		oooMint, oooMaxt         int64
		// After compaction.
		blockRanges        [][2]int64
		headMint, headMaxt int64
	}{
		{
			300, 490,
			489, 489,
			[][2]int64{{300, 360}, {480, 600}},
			360, 490,
		},
		{
			300, 490,
			479, 479,
			[][2]int64{{300, 360}, {360, 480}},
			360, 490,
		},
	}

	for i, c := range cases {
		t.Run(fmt.Sprintf("case=%d", i), func(t *testing.T) {
			dir := t.TempDir()
			ctx := context.Background()

			opts := DefaultOptions()
			opts.OutOfOrderTimeWindow = 30 * time.Minute.Milliseconds()

			db, err := Open(dir, nil, nil, opts, nil)
			require.NoError(t, err)
			db.DisableCompactions()
			t.Cleanup(func() {
				require.NoError(t, db.Close())
			})

			// 3h10m=190m worth in-order data.
			addSamples(t, db, c.inOrderMint, c.inOrderMaxt, true)
			verifySamples(t, db, c.inOrderMint, c.inOrderMaxt)

			// One ooo samples.
			addSamples(t, db, c.oooMint, c.oooMaxt, true)
			verifySamples(t, db, c.inOrderMint, c.inOrderMaxt)

			// We get 2 blocks. 1 from OOO, 1 from in-order.
			require.NoError(t, db.Compact(ctx))
			verifyBlockRanges := func() {
				blocks := db.Blocks()
				require.Equal(t, len(c.blockRanges), len(blocks))
				for j, br := range c.blockRanges {
					require.Equal(t, br[0]*time.Minute.Milliseconds(), blocks[j].MinTime())
					require.Equal(t, br[1]*time.Minute.Milliseconds(), blocks[j].MaxTime())
				}
			}
			verifyBlockRanges()
			require.Equal(t, c.headMint*time.Minute.Milliseconds(), db.head.MinTime())
			require.Equal(t, c.headMaxt*time.Minute.Milliseconds(), db.head.MaxTime())

			// Restart and expect all samples to be present.
			require.NoError(t, db.Close())

			db, err = Open(dir, nil, nil, opts, nil)
			require.NoError(t, err)
			db.DisableCompactions()

			verifyBlockRanges()
			require.Equal(t, c.headMint*time.Minute.Milliseconds(), db.head.MinTime())
			require.Equal(t, c.headMaxt*time.Minute.Milliseconds(), db.head.MaxTime())
			verifySamples(t, db, c.inOrderMint, c.inOrderMaxt)
		})
	}
}

func TestWblReplayAfterOOODisableAndRestart(t *testing.T) {
	dir := t.TempDir()

	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 60 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	var allSamples []chunks.Sample
	addSamples := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			allSamples = append(allSamples, sample{t: ts, f: float64(ts)})
		}
		require.NoError(t, app.Commit())
	}

	// In-order samples.
	addSamples(290, 300)
	// OOO samples.
	addSamples(250, 260)

	verifySamples := func(expSamples []chunks.Sample) {
		sort.Slice(expSamples, func(i, j int) bool {
			return expSamples[i].T() < expSamples[j].T()
		})

		expRes := map[string][]chunks.Sample{
			series1.String(): expSamples,
		}

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)

		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
		require.Equal(t, expRes, actRes)
	}

	verifySamples(allSamples)

	// Restart DB with OOO disabled.
	require.NoError(t, db.Close())
	opts.OutOfOrderTimeWindow = 0
	db, err = Open(db.dir, nil, nil, opts, nil)
	require.NoError(t, err)

	// We can still query OOO samples when OOO is disabled.
	verifySamples(allSamples)
}

func TestPanicOnApplyConfig(t *testing.T) {
	dir := t.TempDir()

	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 60 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	var allSamples []chunks.Sample
	addSamples := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			allSamples = append(allSamples, sample{t: ts, f: float64(ts)})
		}
		require.NoError(t, app.Commit())
	}

	// In-order samples.
	addSamples(290, 300)
	// OOO samples.
	addSamples(250, 260)

	// Restart DB with OOO disabled.
	require.NoError(t, db.Close())
	opts.OutOfOrderTimeWindow = 0
	db, err = Open(db.dir, nil, prometheus.NewRegistry(), opts, nil)
	require.NoError(t, err)

	// ApplyConfig with OOO enabled and expect no panic.
	err = db.ApplyConfig(&config.Config{
		StorageConfig: config.StorageConfig{
			TSDBConfig: &config.TSDBConfig{
				OutOfOrderTimeWindow: 60 * time.Minute.Milliseconds(),
			},
		},
	})
	require.NoError(t, err)
}

func TestDiskFillingUpAfterDisablingOOO(t *testing.T) {
	dir := t.TempDir()
	ctx := context.Background()

	opts := DefaultOptions()
	opts.OutOfOrderTimeWindow = 60 * time.Minute.Milliseconds()

	db, err := Open(dir, nil, nil, opts, nil)
	require.NoError(t, err)
	db.DisableCompactions()
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	series1 := labels.FromStrings("foo", "bar1")
	var allSamples []chunks.Sample
	addSamples := func(fromMins, toMins int64) {
		app := db.Appender(context.Background())
		for min := fromMins; min <= toMins; min++ {
			ts := min * time.Minute.Milliseconds()
			_, err := app.Append(0, series1, ts, float64(ts))
			require.NoError(t, err)
			allSamples = append(allSamples, sample{t: ts, f: float64(ts)})
		}
		require.NoError(t, app.Commit())
	}

	// In-order samples.
	addSamples(290, 300)
	// OOO samples.
	addSamples(250, 299)

	// Restart DB with OOO disabled.
	require.NoError(t, db.Close())
	opts.OutOfOrderTimeWindow = 0
	db, err = Open(db.dir, nil, prometheus.NewRegistry(), opts, nil)
	require.NoError(t, err)
	db.DisableCompactions()

	ms := db.head.series.getByHash(series1.Hash(), series1)
	require.NotEmpty(t, ms.ooo.oooMmappedChunks, "OOO mmap chunk was not replayed")

	checkMmapFileContents := func(contains, notContains []string) {
		mmapDir := mmappedChunksDir(db.head.opts.ChunkDirRoot)
		files, err := os.ReadDir(mmapDir)
		require.NoError(t, err)

		fnames := make([]string, 0, len(files))
		for _, f := range files {
			fnames = append(fnames, f.Name())
		}

		for _, f := range contains {
			require.Contains(t, fnames, f)
		}
		for _, f := range notContains {
			require.NotContains(t, fnames, f)
		}
	}

	// Add in-order samples until ready for compaction..
	addSamples(301, 500)

	// Check that m-map files gets deleted properly after compactions.

	db.head.mmapHeadChunks()
	checkMmapFileContents([]string{"000001", "000002"}, nil)
	require.NoError(t, db.Compact(ctx))
	checkMmapFileContents([]string{"000002"}, []string{"000001"})
	require.Nil(t, ms.ooo, "OOO mmap chunk was not compacted")

	addSamples(501, 650)
	db.head.mmapHeadChunks()
	checkMmapFileContents([]string{"000002", "000003"}, []string{"000001"})
	require.NoError(t, db.Compact(ctx))
	checkMmapFileContents(nil, []string{"000001", "000002", "000003"})

	// Verify that WBL is empty.
	files, err := os.ReadDir(db.head.wbl.Dir())
	require.NoError(t, err)
	require.Len(t, files, 1) // Last empty file after compaction.
	finfo, err := files[0].Info()
	require.NoError(t, err)
	require.Equal(t, int64(0), finfo.Size())
}

func TestHistogramAppendAndQuery(t *testing.T) {
	t.Run("integer histograms", func(t *testing.T) {
		testHistogramAppendAndQueryHelper(t, false)
	})
	t.Run("float histograms", func(t *testing.T) {
		testHistogramAppendAndQueryHelper(t, true)
	})
}

func testHistogramAppendAndQueryHelper(t *testing.T, floatHistogram bool) {
	t.Helper()
	db := openTestDB(t, nil, nil)
	minute := func(m int) int64 { return int64(m) * time.Minute.Milliseconds() }
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})

	ctx := context.Background()
	appendHistogram := func(
		lbls labels.Labels, tsMinute int, h *histogram.Histogram,
		exp *[]chunks.Sample, expCRH histogram.CounterResetHint,
	) {
		t.Helper()
		var err error
		app := db.Appender(ctx)
		if floatHistogram {
			_, err = app.AppendHistogram(0, lbls, minute(tsMinute), nil, h.ToFloat(nil))
			efh := h.ToFloat(nil)
			efh.CounterResetHint = expCRH
			*exp = append(*exp, sample{t: minute(tsMinute), fh: efh})
		} else {
			_, err = app.AppendHistogram(0, lbls, minute(tsMinute), h.Copy(), nil)
			eh := h.Copy()
			eh.CounterResetHint = expCRH
			*exp = append(*exp, sample{t: minute(tsMinute), h: eh})
		}
		require.NoError(t, err)
		require.NoError(t, app.Commit())
	}
	appendFloat := func(lbls labels.Labels, tsMinute int, val float64, exp *[]chunks.Sample) {
		t.Helper()
		app := db.Appender(ctx)
		_, err := app.Append(0, lbls, minute(tsMinute), val)
		require.NoError(t, err)
		require.NoError(t, app.Commit())
		*exp = append(*exp, sample{t: minute(tsMinute), f: val})
	}

	testQuery := func(name, value string, exp map[string][]chunks.Sample) {
		t.Helper()
		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		act := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, name, value))
		require.Equal(t, exp, act)
	}

	baseH := &histogram.Histogram{
		Count:         15,
		ZeroCount:     4,
		ZeroThreshold: 0.001,
		Sum:           35.5,
		Schema:        1,
		PositiveSpans: []histogram.Span{
			{Offset: 0, Length: 2},
			{Offset: 2, Length: 2},
		},
		PositiveBuckets: []int64{1, 1, -1, 0},
		NegativeSpans: []histogram.Span{
			{Offset: 0, Length: 1},
			{Offset: 1, Length: 2},
		},
		NegativeBuckets: []int64{1, 2, -1},
	}

	var (
		series1                = labels.FromStrings("foo", "bar1")
		series2                = labels.FromStrings("foo", "bar2")
		series3                = labels.FromStrings("foo", "bar3")
		series4                = labels.FromStrings("foo", "bar4")
		exp1, exp2, exp3, exp4 []chunks.Sample
	)

	// TODO(codesome): test everything for negative buckets as well.
	t.Run("series with only histograms", func(t *testing.T) {
		h := baseH.Copy() // This is shared across all sub tests.

		appendHistogram(series1, 100, h, &exp1, histogram.UnknownCounterReset)
		testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})

		h.PositiveBuckets[0]++
		h.NegativeBuckets[0] += 2
		h.Count += 10
		appendHistogram(series1, 101, h, &exp1, histogram.NotCounterReset)
		testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})

		t.Run("changing schema", func(t *testing.T) {
			h.Schema = 2
			appendHistogram(series1, 102, h, &exp1, histogram.UnknownCounterReset)
			testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})

			// Schema back to old.
			h.Schema = 1
			appendHistogram(series1, 103, h, &exp1, histogram.UnknownCounterReset)
			testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})
		})

		t.Run("new buckets incoming", func(t *testing.T) {
			// In the previous unit test, during the last histogram append, we
			// changed the schema and  that caused a new chunk creation. Because
			// of the next append the layout of the last histogram will change
			// because the chunk will be re-encoded. So this forces us to modify
			// the last histogram in exp1 so when we query we get the expected
			// results.
			if floatHistogram {
				lh := exp1[len(exp1)-1].FH().Copy()
				lh.PositiveSpans[1].Length++
				lh.PositiveBuckets = append(lh.PositiveBuckets, 0)
				exp1[len(exp1)-1] = sample{t: exp1[len(exp1)-1].T(), fh: lh}
			} else {
				lh := exp1[len(exp1)-1].H().Copy()
				lh.PositiveSpans[1].Length++
				lh.PositiveBuckets = append(lh.PositiveBuckets, -2) // -2 makes the last bucket 0.
				exp1[len(exp1)-1] = sample{t: exp1[len(exp1)-1].T(), h: lh}
			}

			// This histogram with new bucket at the end causes the re-encoding of the previous histogram.
			// Hence the previous histogram is recoded into this new layout.
			// But the query returns the histogram from the in-memory buffer, hence we don't see the recode here yet.
			h.PositiveSpans[1].Length++
			h.PositiveBuckets = append(h.PositiveBuckets, 1)
			h.Count += 3
			appendHistogram(series1, 104, h, &exp1, histogram.NotCounterReset)
			testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})

			// Because of the previous two histograms being on the active chunk,
			// and the next append is only adding a new bucket, the active chunk
			// will be re-encoded to the new layout.
			if floatHistogram {
				lh := exp1[len(exp1)-2].FH().Copy()
				lh.PositiveSpans[0].Length++
				lh.PositiveSpans[1].Offset--
				lh.PositiveBuckets = []float64{2, 3, 0, 2, 2, 0}
				exp1[len(exp1)-2] = sample{t: exp1[len(exp1)-2].T(), fh: lh}

				lh = exp1[len(exp1)-1].FH().Copy()
				lh.PositiveSpans[0].Length++
				lh.PositiveSpans[1].Offset--
				lh.PositiveBuckets = []float64{2, 3, 0, 2, 2, 3}
				exp1[len(exp1)-1] = sample{t: exp1[len(exp1)-1].T(), fh: lh}
			} else {
				lh := exp1[len(exp1)-2].H().Copy()
				lh.PositiveSpans[0].Length++
				lh.PositiveSpans[1].Offset--
				lh.PositiveBuckets = []int64{2, 1, -3, 2, 0, -2}
				exp1[len(exp1)-2] = sample{t: exp1[len(exp1)-2].T(), h: lh}

				lh = exp1[len(exp1)-1].H().Copy()
				lh.PositiveSpans[0].Length++
				lh.PositiveSpans[1].Offset--
				lh.PositiveBuckets = []int64{2, 1, -3, 2, 0, 1}
				exp1[len(exp1)-1] = sample{t: exp1[len(exp1)-1].T(), h: lh}
			}

			// Now we add the new buckets in between. Empty bucket is again not present for the old histogram.
			h.PositiveSpans[0].Length++
			h.PositiveSpans[1].Offset--
			h.Count += 3
			// {2, 1, -1, 0, 1} -> {2, 1, 0, -1, 0, 1}
			h.PositiveBuckets = append(h.PositiveBuckets[:2], append([]int64{0}, h.PositiveBuckets[2:]...)...)
			appendHistogram(series1, 105, h, &exp1, histogram.NotCounterReset)
			testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})

			// We add 4 more histograms to clear out the buffer and see the re-encoded histograms.
			appendHistogram(series1, 106, h, &exp1, histogram.NotCounterReset)
			appendHistogram(series1, 107, h, &exp1, histogram.NotCounterReset)
			appendHistogram(series1, 108, h, &exp1, histogram.NotCounterReset)
			appendHistogram(series1, 109, h, &exp1, histogram.NotCounterReset)

			// Update the expected histograms to reflect the re-encoding.
			if floatHistogram {
				l := len(exp1)
				h7 := exp1[l-7].FH()
				h7.PositiveSpans = exp1[l-1].FH().PositiveSpans
				h7.PositiveBuckets = []float64{2, 3, 0, 2, 2, 0}
				exp1[l-7] = sample{t: exp1[l-7].T(), fh: h7}

				h6 := exp1[l-6].FH()
				h6.PositiveSpans = exp1[l-1].FH().PositiveSpans
				h6.PositiveBuckets = []float64{2, 3, 0, 2, 2, 3}
				exp1[l-6] = sample{t: exp1[l-6].T(), fh: h6}
			} else {
				l := len(exp1)
				h7 := exp1[l-7].H()
				h7.PositiveSpans = exp1[l-1].H().PositiveSpans
				h7.PositiveBuckets = []int64{2, 1, -3, 2, 0, -2} // -3 and -2 are the empty buckets.
				exp1[l-7] = sample{t: exp1[l-7].T(), h: h7}

				h6 := exp1[l-6].H()
				h6.PositiveSpans = exp1[l-1].H().PositiveSpans
				h6.PositiveBuckets = []int64{2, 1, -3, 2, 0, 1} // -3 is the empty bucket.
				exp1[l-6] = sample{t: exp1[l-6].T(), h: h6}
			}

			testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})
		})

		t.Run("buckets disappearing", func(t *testing.T) {
			h.PositiveSpans[1].Length--
			h.PositiveBuckets = h.PositiveBuckets[:len(h.PositiveBuckets)-1]
			h.Count -= 3
			appendHistogram(series1, 110, h, &exp1, histogram.CounterReset)
			testQuery("foo", "bar1", map[string][]chunks.Sample{series1.String(): exp1})
		})
	})

	t.Run("series starting with float and then getting histograms", func(t *testing.T) {
		appendFloat(series2, 100, 100, &exp2)
		appendFloat(series2, 101, 101, &exp2)
		appendFloat(series2, 102, 102, &exp2)
		testQuery("foo", "bar2", map[string][]chunks.Sample{series2.String(): exp2})

		h := baseH.Copy()
		appendHistogram(series2, 103, h, &exp2, histogram.UnknownCounterReset)
		appendHistogram(series2, 104, h, &exp2, histogram.NotCounterReset)
		appendHistogram(series2, 105, h, &exp2, histogram.NotCounterReset)
		testQuery("foo", "bar2", map[string][]chunks.Sample{series2.String(): exp2})

		// Switching between float and histograms again.
		appendFloat(series2, 106, 106, &exp2)
		appendFloat(series2, 107, 107, &exp2)
		testQuery("foo", "bar2", map[string][]chunks.Sample{series2.String(): exp2})

		appendHistogram(series2, 108, h, &exp2, histogram.UnknownCounterReset)
		appendHistogram(series2, 109, h, &exp2, histogram.NotCounterReset)
		testQuery("foo", "bar2", map[string][]chunks.Sample{series2.String(): exp2})
	})

	t.Run("series starting with histogram and then getting float", func(t *testing.T) {
		h := baseH.Copy()
		appendHistogram(series3, 101, h, &exp3, histogram.UnknownCounterReset)
		appendHistogram(series3, 102, h, &exp3, histogram.NotCounterReset)
		appendHistogram(series3, 103, h, &exp3, histogram.NotCounterReset)
		testQuery("foo", "bar3", map[string][]chunks.Sample{series3.String(): exp3})

		appendFloat(series3, 104, 100, &exp3)
		appendFloat(series3, 105, 101, &exp3)
		appendFloat(series3, 106, 102, &exp3)
		testQuery("foo", "bar3", map[string][]chunks.Sample{series3.String(): exp3})

		// Switching between histogram and float again.
		appendHistogram(series3, 107, h, &exp3, histogram.UnknownCounterReset)
		appendHistogram(series3, 108, h, &exp3, histogram.NotCounterReset)
		testQuery("foo", "bar3", map[string][]chunks.Sample{series3.String(): exp3})

		appendFloat(series3, 109, 106, &exp3)
		appendFloat(series3, 110, 107, &exp3)
		testQuery("foo", "bar3", map[string][]chunks.Sample{series3.String(): exp3})
	})

	t.Run("query mix of histogram and float series", func(t *testing.T) {
		// A float only series.
		appendFloat(series4, 100, 100, &exp4)
		appendFloat(series4, 101, 101, &exp4)
		appendFloat(series4, 102, 102, &exp4)

		testQuery("foo", "bar.*", map[string][]chunks.Sample{
			series1.String(): exp1,
			series2.String(): exp2,
			series3.String(): exp3,
			series4.String(): exp4,
		})
	})
}

func TestQueryHistogramFromBlocksWithCompaction(t *testing.T) {
	minute := func(m int) int64 { return int64(m) * time.Minute.Milliseconds() }

	testBlockQuerying := func(t *testing.T, blockSeries ...[]storage.Series) {
		t.Helper()

		opts := DefaultOptions()
		db := openTestDB(t, opts, nil)
		t.Cleanup(func() {
			require.NoError(t, db.Close())
		})

		var it chunkenc.Iterator
		exp := make(map[string][]chunks.Sample)
		for _, series := range blockSeries {
			createBlock(t, db.Dir(), series)

			for _, s := range series {
				key := s.Labels().String()
				it = s.Iterator(it)
				slice := exp[key]
				for typ := it.Next(); typ != chunkenc.ValNone; typ = it.Next() {
					switch typ {
					case chunkenc.ValFloat:
						ts, v := it.At()
						slice = append(slice, sample{t: ts, f: v})
					case chunkenc.ValHistogram:
						ts, h := it.AtHistogram(nil)
						slice = append(slice, sample{t: ts, h: h})
					case chunkenc.ValFloatHistogram:
						ts, h := it.AtFloatHistogram(nil)
						slice = append(slice, sample{t: ts, fh: h})
					default:
						t.Fatalf("unexpected sample value type %d", typ)
					}
				}
				sort.Slice(slice, func(i, j int) bool {
					return slice[i].T() < slice[j].T()
				})
				exp[key] = slice
			}
		}

		require.Empty(t, db.Blocks())
		require.NoError(t, db.reload())
		require.Len(t, db.Blocks(), len(blockSeries))

		q, err := db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		res := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "__name__", ".*"))
		compareSeries(t, exp, res)

		// Compact all the blocks together and query again.
		blocks := db.Blocks()
		blockDirs := make([]string, 0, len(blocks))
		for _, b := range blocks {
			blockDirs = append(blockDirs, b.Dir())
		}
		id, err := db.compactor.Compact(db.Dir(), blockDirs, blocks)
		require.NoError(t, err)
		require.NotEqual(t, ulid.ULID{}, id)
		require.NoError(t, db.reload())
		require.Len(t, db.Blocks(), 1)

		q, err = db.Querier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		res = query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "__name__", ".*"))

		// After compaction, we do not require "unknown" counter resets
		// due to origin from different overlapping chunks anymore.
		for _, ss := range exp {
			for i, s := range ss[1:] {
				if s.H() != nil && ss[i].H() != nil && s.H().CounterResetHint == histogram.UnknownCounterReset {
					s.H().CounterResetHint = histogram.NotCounterReset
				}
				if s.FH() != nil && ss[i].FH() != nil && s.FH().CounterResetHint == histogram.UnknownCounterReset {
					s.FH().CounterResetHint = histogram.NotCounterReset
				}
			}
		}
		compareSeries(t, exp, res)
	}

	for _, floatHistogram := range []bool{false, true} {
		t.Run(fmt.Sprintf("floatHistogram=%t", floatHistogram), func(t *testing.T) {
			t.Run("serial blocks with only histograms", func(t *testing.T) {
				testBlockQuerying(t,
					genHistogramSeries(10, 5, minute(0), minute(119), minute(1), floatHistogram),
					genHistogramSeries(10, 5, minute(120), minute(239), minute(1), floatHistogram),
					genHistogramSeries(10, 5, minute(240), minute(359), minute(1), floatHistogram),
				)
			})

			t.Run("serial blocks with either histograms or floats in a block and not both", func(t *testing.T) {
				testBlockQuerying(t,
					genHistogramSeries(10, 5, minute(0), minute(119), minute(1), floatHistogram),
					genSeriesFromSampleGenerator(10, 5, minute(120), minute(239), minute(1), func(ts int64) chunks.Sample {
						return sample{t: ts, f: rand.Float64()}
					}),
					genHistogramSeries(10, 5, minute(240), minute(359), minute(1), floatHistogram),
				)
			})

			t.Run("serial blocks with mix of histograms and float64", func(t *testing.T) {
				testBlockQuerying(t,
					genHistogramAndFloatSeries(10, 5, minute(0), minute(60), minute(1), floatHistogram),
					genHistogramSeries(10, 5, minute(61), minute(120), minute(1), floatHistogram),
					genHistogramAndFloatSeries(10, 5, minute(121), minute(180), minute(1), floatHistogram),
					genSeriesFromSampleGenerator(10, 5, minute(181), minute(240), minute(1), func(ts int64) chunks.Sample {
						return sample{t: ts, f: rand.Float64()}
					}),
				)
			})

			t.Run("overlapping blocks with only histograms", func(t *testing.T) {
				testBlockQuerying(t,
					genHistogramSeries(10, 5, minute(0), minute(120), minute(3), floatHistogram),
					genHistogramSeries(10, 5, minute(1), minute(120), minute(3), floatHistogram),
					genHistogramSeries(10, 5, minute(2), minute(120), minute(3), floatHistogram),
				)
			})

			t.Run("overlapping blocks with only histograms and only float in a series", func(t *testing.T) {
				testBlockQuerying(t,
					genHistogramSeries(10, 5, minute(0), minute(120), minute(3), floatHistogram),
					genSeriesFromSampleGenerator(10, 5, minute(1), minute(120), minute(3), func(ts int64) chunks.Sample {
						return sample{t: ts, f: rand.Float64()}
					}),
					genHistogramSeries(10, 5, minute(2), minute(120), minute(3), floatHistogram),
				)
			})

			t.Run("overlapping blocks with mix of histograms and float64", func(t *testing.T) {
				testBlockQuerying(t,
					genHistogramAndFloatSeries(10, 5, minute(0), minute(60), minute(3), floatHistogram),
					genHistogramSeries(10, 5, minute(46), minute(100), minute(3), floatHistogram),
					genHistogramAndFloatSeries(10, 5, minute(89), minute(140), minute(3), floatHistogram),
					genSeriesFromSampleGenerator(10, 5, minute(126), minute(200), minute(3), func(ts int64) chunks.Sample {
						return sample{t: ts, f: rand.Float64()}
					}),
				)
			})
		})
	}
}

func TestNativeHistogramFlag(t *testing.T) {
	dir := t.TempDir()
	db, err := Open(dir, nil, nil, nil, nil)
	require.NoError(t, err)
	t.Cleanup(func() {
		require.NoError(t, db.Close())
	})
	h := &histogram.Histogram{
		Count:         9,
		ZeroCount:     4,
		ZeroThreshold: 0.001,
		Sum:           35.5,
		Schema:        1,
		PositiveSpans: []histogram.Span{
			{Offset: 0, Length: 2},
			{Offset: 2, Length: 2},
		},
		PositiveBuckets: []int64{1, 1, -1, 0},
	}

	l := labels.FromStrings("foo", "bar")

	app := db.Appender(context.Background())

	// Disabled by default.
	_, err = app.AppendHistogram(0, l, 100, h, nil)
	require.Equal(t, storage.ErrNativeHistogramsDisabled, err)
	_, err = app.AppendHistogram(0, l, 105, nil, h.ToFloat(nil))
	require.Equal(t, storage.ErrNativeHistogramsDisabled, err)

	// Enable and append.
	db.EnableNativeHistograms()
	_, err = app.AppendHistogram(0, l, 200, h, nil)
	require.NoError(t, err)
	_, err = app.AppendHistogram(0, l, 205, nil, h.ToFloat(nil))
	require.NoError(t, err)

	db.DisableNativeHistograms()
	_, err = app.AppendHistogram(0, l, 300, h, nil)
	require.Equal(t, storage.ErrNativeHistogramsDisabled, err)
	_, err = app.AppendHistogram(0, l, 305, nil, h.ToFloat(nil))
	require.Equal(t, storage.ErrNativeHistogramsDisabled, err)

	require.NoError(t, app.Commit())

	q, err := db.Querier(math.MinInt, math.MaxInt64)
	require.NoError(t, err)
	act := query(t, q, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
	require.Equal(t, map[string][]chunks.Sample{
		l.String(): {sample{t: 200, h: h}, sample{t: 205, fh: h.ToFloat(nil)}},
	}, act)
}

// compareSeries essentially replaces `require.Equal(t, expected, actual) in
// situations where the actual series might contain more counter reset hints
// "unknown" than the expected series. This can easily happen for long series
// that trigger new chunks. This function therefore tolerates counter reset
// hints "CounterReset" and "NotCounterReset" in an expected series where the
// actual series contains a counter reset hint "UnknownCounterReset".
// "GaugeType" hints are still strictly checked, and any "UnknownCounterReset"
// in an expected series has to be matched precisely by the actual series.
func compareSeries(t require.TestingT, expected, actual map[string][]chunks.Sample) {
	if len(expected) != len(actual) {
		// The reason for the difference is not the counter reset hints
		// (alone), so let's use the pretty diffing by the require
		// package.
		require.Equal(t, expected, actual, "number of series differs")
	}
	for key, eSamples := range expected {
		aSamples, ok := actual[key]
		if !ok {
			require.Equal(t, expected, actual, "expected series %q not found", key)
		}
		if len(eSamples) != len(aSamples) {
			require.Equal(t, eSamples, aSamples, "number of samples for series %q differs", key)
		}
		for i, eS := range eSamples {
			aS := aSamples[i]
			aH, eH := aS.H(), eS.H()
			aFH, eFH := aS.FH(), eS.FH()
			switch {
			case aH != nil && eH != nil && aH.CounterResetHint == histogram.UnknownCounterReset && eH.CounterResetHint != histogram.GaugeType:
				eH = eH.Copy()
				eH.CounterResetHint = histogram.UnknownCounterReset
				eS = sample{t: eS.T(), h: eH}
			case aFH != nil && eFH != nil && aFH.CounterResetHint == histogram.UnknownCounterReset && eFH.CounterResetHint != histogram.GaugeType:
				eFH = eFH.Copy()
				eFH.CounterResetHint = histogram.UnknownCounterReset
				eS = sample{t: eS.T(), fh: eFH}
			}
			require.Equal(t, eS, aS, "sample %d in series %q differs", i, key)
		}
	}
}

// TestChunkQuerierReadWriteRace looks for any possible race between appending
// samples and reading chunks because the head chunk that is being appended to
// can be read in parallel and we should be able to make a copy of the chunk without
// worrying about the parallel write.
func TestChunkQuerierReadWriteRace(t *testing.T) {
	db := openTestDB(t, nil, nil)
	defer func() {
		require.NoError(t, db.Close())
	}()

	lbls := labels.FromStrings("foo", "bar")

	writer := func() error {
		<-time.After(5 * time.Millisecond) // Initial pause while readers start.
		ts := 0
		for i := 0; i < 500; i++ {
			app := db.Appender(context.Background())
			for j := 0; j < 10; j++ {
				ts++
				_, err := app.Append(0, lbls, int64(ts), float64(ts*100))
				if err != nil {
					return err
				}
			}
			err := app.Commit()
			if err != nil {
				return err
			}
			<-time.After(time.Millisecond)
		}
		return nil
	}

	reader := func() {
		querier, err := db.ChunkQuerier(math.MinInt64, math.MaxInt64)
		require.NoError(t, err)
		defer func(q storage.ChunkQuerier) {
			require.NoError(t, q.Close())
		}(querier)
		ss := querier.Select(context.Background(), false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
		for ss.Next() {
			cs := ss.At()
			it := cs.Iterator(nil)
			for it.Next() {
				m := it.At()
				b := m.Chunk.Bytes()
				bb := make([]byte, len(b))
				copy(bb, b) // This copying of chunk bytes detects any race.
			}
		}
		require.NoError(t, ss.Err())
	}

	ch := make(chan struct{})
	var writerErr error
	go func() {
		defer close(ch)
		writerErr = writer()
	}()

Outer:
	for {
		reader()
		select {
		case <-ch:
			break Outer
		default:
		}
	}

	require.NoError(t, writerErr)
}

func requireEqualOOOSamples(t *testing.T, expectedSamples int, db *DB) {
	require.Equal(t, float64(expectedSamples),
		prom_testutil.ToFloat64(db.head.metrics.outOfOrderSamplesAppended.WithLabelValues(sampleMetricTypeFloat)),
		"number of ooo appended samples mismatch")
}
