ceremonyclient/pebble/compaction.go

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2024-01-03 07:31:42 +00:00
// Copyright 2013 The LevelDB-Go and Pebble Authors. All rights reserved. Use
// of this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
package pebble
import (
"bytes"
"context"
"fmt"
"io"
"math"
"runtime/pprof"
"sort"
"sync/atomic"
"time"
"github.com/cockroachdb/errors"
"github.com/cockroachdb/pebble/internal/base"
"github.com/cockroachdb/pebble/internal/invalidating"
"github.com/cockroachdb/pebble/internal/invariants"
"github.com/cockroachdb/pebble/internal/keyspan"
"github.com/cockroachdb/pebble/internal/manifest"
"github.com/cockroachdb/pebble/internal/private"
"github.com/cockroachdb/pebble/internal/rangedel"
"github.com/cockroachdb/pebble/internal/rangekey"
"github.com/cockroachdb/pebble/objstorage"
"github.com/cockroachdb/pebble/objstorage/objstorageprovider/objiotracing"
"github.com/cockroachdb/pebble/objstorage/remote"
"github.com/cockroachdb/pebble/shims/cmp"
"github.com/cockroachdb/pebble/shims/slices"
"github.com/cockroachdb/pebble/sstable"
"github.com/cockroachdb/pebble/vfs"
)
var errEmptyTable = errors.New("pebble: empty table")
// ErrCancelledCompaction is returned if a compaction is cancelled by a
// concurrent excise or ingest-split operation.
var ErrCancelledCompaction = errors.New("pebble: compaction cancelled by a concurrent operation, will retry compaction")
var compactLabels = pprof.Labels("pebble", "compact")
var flushLabels = pprof.Labels("pebble", "flush")
var gcLabels = pprof.Labels("pebble", "gc")
// getInternalWriterProperties accesses a private variable (in the
// internal/private package) initialized by the sstable Writer. This indirection
// is necessary to ensure non-Pebble users constructing sstables for ingestion
// are unable to set internal-only properties.
var getInternalWriterProperties = private.SSTableInternalProperties.(func(*sstable.Writer) *sstable.Properties)
// expandedCompactionByteSizeLimit is the maximum number of bytes in all
// compacted files. We avoid expanding the lower level file set of a compaction
// if it would make the total compaction cover more than this many bytes.
func expandedCompactionByteSizeLimit(opts *Options, level int, availBytes uint64) uint64 {
v := uint64(25 * opts.Level(level).TargetFileSize)
// Never expand a compaction beyond half the available capacity, divided
// by the maximum number of concurrent compactions. Each of the concurrent
// compactions may expand up to this limit, so this attempts to limit
// compactions to half of available disk space. Note that this will not
// prevent compaction picking from pursuing compactions that are larger
// than this threshold before expansion.
diskMax := (availBytes / 2) / uint64(opts.MaxConcurrentCompactions())
if v > diskMax {
v = diskMax
}
return v
}
// maxGrandparentOverlapBytes is the maximum bytes of overlap with level+1
// before we stop building a single file in a level-1 to level compaction.
func maxGrandparentOverlapBytes(opts *Options, level int) uint64 {
return uint64(10 * opts.Level(level).TargetFileSize)
}
// maxReadCompactionBytes is used to prevent read compactions which
// are too wide.
func maxReadCompactionBytes(opts *Options, level int) uint64 {
return uint64(10 * opts.Level(level).TargetFileSize)
}
// noCloseIter wraps around a FragmentIterator, intercepting and eliding
// calls to Close. It is used during compaction to ensure that rangeDelIters
// are not closed prematurely.
type noCloseIter struct {
keyspan.FragmentIterator
}
func (i noCloseIter) Close() error {
return nil
}
type compactionLevel struct {
level int
files manifest.LevelSlice
// l0SublevelInfo contains information about L0 sublevels being compacted.
// It's only set for the start level of a compaction starting out of L0 and
// is nil for all other compactions.
l0SublevelInfo []sublevelInfo
}
func (cl compactionLevel) Clone() compactionLevel {
newCL := compactionLevel{
level: cl.level,
files: cl.files.Reslice(func(start, end *manifest.LevelIterator) {}),
}
return newCL
}
func (cl compactionLevel) String() string {
return fmt.Sprintf(`Level %d, Files %s`, cl.level, cl.files)
}
// Return output from compactionOutputSplitters. See comment on
// compactionOutputSplitter.shouldSplitBefore() on how this value is used.
type maybeSplit int
const (
noSplit maybeSplit = iota
splitNow
)
// String implements the Stringer interface.
func (c maybeSplit) String() string {
if c == noSplit {
return "no-split"
}
return "split-now"
}
// compactionOutputSplitter is an interface for encapsulating logic around
// switching the output of a compaction to a new output file. Additional
// constraints around switching compaction outputs that are specific to that
// compaction type (eg. flush splits) are implemented in
// compactionOutputSplitters that compose other child compactionOutputSplitters.
type compactionOutputSplitter interface {
// shouldSplitBefore returns whether we should split outputs before the
// specified "current key". The return value is splitNow or noSplit.
// splitNow means a split is advised before the specified key, and noSplit
// means no split is advised. If shouldSplitBefore(a) advises a split then
// shouldSplitBefore(b) should also advise a split given b >= a, until
// onNewOutput is called.
shouldSplitBefore(key *InternalKey, tw *sstable.Writer) maybeSplit
// onNewOutput updates internal splitter state when the compaction switches
// to a new sstable, and returns the next limit for the new output which
// would get used to truncate range tombstones if the compaction iterator
// runs out of keys. The limit returned MUST be > key according to the
// compaction's comparator. The specified key is the first key in the new
// output, or nil if this sstable will only contain range tombstones already
// in the fragmenter.
onNewOutput(key []byte) []byte
}
// fileSizeSplitter is a compactionOutputSplitter that enforces target file
// sizes. This splitter splits to a new output file when the estimated file size
// is 0.5x-2x the target file size. If there are overlapping grandparent files,
// this splitter will attempt to split at a grandparent boundary. For example,
// consider the example where a compaction wrote 'd' to the current output file,
// and the next key has a user key 'g':
//
// previous key next key
// | |
// | |
// +---------------|----+ +--|----------+
// grandparents: | 000006 | | | | 000007 |
// +---------------|----+ +--|----------+
// a b d e f g i
//
// Splitting the output file F before 'g' will ensure that the current output
// file F does not overlap the grandparent file 000007. Aligning sstable
// boundaries like this can significantly reduce write amplification, since a
// subsequent compaction of F into the grandparent level will avoid needlessly
// rewriting any keys within 000007 that do not overlap F's bounds. Consider the
// following compaction:
//
// +----------------------+
// input | |
// level +----------------------+
// \/
// +---------------+ +---------------+
// output |XXXXXXX| | | |XXXXXXXX|
// level +---------------+ +---------------+
//
// The input-level file overlaps two files in the output level, but only
// partially. The beginning of the first output-level file and the end of the
// second output-level file will be rewritten verbatim. This write I/O is
// "wasted" in the sense that no merging is being performed.
//
// To prevent the above waste, this splitter attempts to split output files
// before the start key of grandparent files. It still strives to write output
// files of approximately the target file size, by constraining this splitting
// at grandparent points to apply only if the current output's file size is
// about the right order of magnitude.
//
// Note that, unlike most other splitters, this splitter does not guarantee that
// it will advise splits only at user key change boundaries.
type fileSizeSplitter struct {
frontier frontier
targetFileSize uint64
atGrandparentBoundary bool
boundariesObserved uint64
nextGrandparent *fileMetadata
grandparents manifest.LevelIterator
}
func newFileSizeSplitter(
f *frontiers, targetFileSize uint64, grandparents manifest.LevelIterator,
) *fileSizeSplitter {
s := &fileSizeSplitter{targetFileSize: targetFileSize}
s.nextGrandparent = grandparents.First()
s.grandparents = grandparents
if s.nextGrandparent != nil {
s.frontier.Init(f, s.nextGrandparent.Smallest.UserKey, s.reached)
}
return s
}
func (f *fileSizeSplitter) reached(nextKey []byte) []byte {
f.atGrandparentBoundary = true
f.boundariesObserved++
// NB: f.grandparents is a bounded iterator, constrained to the compaction
// key range.
f.nextGrandparent = f.grandparents.Next()
if f.nextGrandparent == nil {
return nil
}
// TODO(jackson): Should we also split before or immediately after
// grandparents' largest keys? Splitting before the start boundary prevents
// overlap with the grandparent. Also splitting after the end boundary may
// increase the probability of move compactions.
return f.nextGrandparent.Smallest.UserKey
}
func (f *fileSizeSplitter) shouldSplitBefore(key *InternalKey, tw *sstable.Writer) maybeSplit {
atGrandparentBoundary := f.atGrandparentBoundary
// Clear f.atGrandparentBoundary unconditionally.
//
// This is a bit subtle. Even if do decide to split, it's possible that a
// higher-level splitter will ignore our request (eg, because we're between
// two internal keys with the same user key). In this case, the next call to
// shouldSplitBefore will find atGrandparentBoundary=false. This is
// desirable, because in this case we would've already written the earlier
// key with the same user key to the output file. The current output file is
// already doomed to overlap the grandparent whose bound triggered
// atGrandparentBoundary=true. We should continue on, waiting for the next
// grandparent boundary.
f.atGrandparentBoundary = false
// If the key is a range tombstone, the EstimatedSize may not grow right
// away when a range tombstone is added to the fragmenter: It's dependent on
// whether or not the this new range deletion will start a new fragment.
// Range deletions are rare, so we choose to simply not split yet.
// TODO(jackson): Reconsider this, and consider range keys too as a part of
// #2321.
if key.Kind() == InternalKeyKindRangeDelete || tw == nil {
return noSplit
}
estSize := tw.EstimatedSize()
switch {
case estSize < f.targetFileSize/2:
// The estimated file size is less than half the target file size. Don't
// split it, even if currently aligned with a grandparent file because
// it's too small.
return noSplit
case estSize >= 2*f.targetFileSize:
// The estimated file size is double the target file size. Split it even
// if we were not aligned with a grandparent file boundary to avoid
// excessively exceeding the target file size.
return splitNow
case !atGrandparentBoundary:
// Don't split if we're not at a grandparent, except if we've exhausted
// all the grandparents overlapping this compaction's key range. Then we
// may want to split purely based on file size.
if f.nextGrandparent == nil {
// There are no more grandparents. Optimize for the target file size
// and split as soon as we hit the target file size.
if estSize >= f.targetFileSize {
return splitNow
}
}
return noSplit
default:
// INVARIANT: atGrandparentBoundary
// INVARIANT: targetSize/2 < estSize < 2*targetSize
//
// The estimated file size is close enough to the target file size that
// we should consider splitting.
//
// Determine whether to split now based on how many grandparent
// boundaries we have already observed while building this output file.
// The intuition here is that if the grandparent level is dense in this
// part of the keyspace, we're likely to continue to have more
// opportunities to split this file aligned with a grandparent. If this
// is the first grandparent boundary observed, we split immediately
// (we're already at ≥50% the target file size). Otherwise, each
// overlapping grandparent we've observed increases the minimum file
// size by 5% of the target file size, up to at most 90% of the target
// file size.
//
// TODO(jackson): The particular thresholds are somewhat unprincipled.
// This is the same heuristic as RocksDB implements. Is there are more
// principled formulation that can, further reduce w-amp, produce files
// closer to the target file size, or is more understandable?
// NB: Subtract 1 from `boundariesObserved` to account for the current
// boundary we're considering splitting at. `reached` will have
// incremented it at the same time it set `atGrandparentBoundary`.
minBoundaries := f.boundariesObserved-1
if minBoundaries > 8 {
minBoundaries = 8
}
minimumPctOfTargetSize := 50 + 5*minBoundaries
if estSize < (minimumPctOfTargetSize*f.targetFileSize)/100 {
return noSplit
}
return splitNow
}
}
func (f *fileSizeSplitter) onNewOutput(key []byte) []byte {
f.boundariesObserved = 0
return nil
}
func newLimitFuncSplitter(f *frontiers, limitFunc func(userKey []byte) []byte) *limitFuncSplitter {
s := &limitFuncSplitter{limitFunc: limitFunc}
s.frontier.Init(f, nil, s.reached)
return s
}
type limitFuncSplitter struct {
frontier frontier
limitFunc func(userKey []byte) []byte
split maybeSplit
}
func (lf *limitFuncSplitter) shouldSplitBefore(key *InternalKey, tw *sstable.Writer) maybeSplit {
return lf.split
}
func (lf *limitFuncSplitter) reached(nextKey []byte) []byte {
lf.split = splitNow
return nil
}
func (lf *limitFuncSplitter) onNewOutput(key []byte) []byte {
lf.split = noSplit
if key != nil {
// TODO(jackson): For some users, like L0 flush splits, there's no need
// to binary search over all the flush splits every time. The next split
// point must be ahead of the previous flush split point.
limit := lf.limitFunc(key)
lf.frontier.Update(limit)
return limit
}
lf.frontier.Update(nil)
return nil
}
// splitterGroup is a compactionOutputSplitter that splits whenever one of its
// child splitters advises a compaction split.
type splitterGroup struct {
cmp Compare
splitters []compactionOutputSplitter
}
func (a *splitterGroup) shouldSplitBefore(
key *InternalKey, tw *sstable.Writer,
) (suggestion maybeSplit) {
for _, splitter := range a.splitters {
if splitter.shouldSplitBefore(key, tw) == splitNow {
return splitNow
}
}
return noSplit
}
func (a *splitterGroup) onNewOutput(key []byte) []byte {
var earliestLimit []byte
for _, splitter := range a.splitters {
limit := splitter.onNewOutput(key)
if limit == nil {
continue
}
if earliestLimit == nil || a.cmp(limit, earliestLimit) < 0 {
earliestLimit = limit
}
}
return earliestLimit
}
// userKeyChangeSplitter is a compactionOutputSplitter that takes in a child
// splitter, and splits when 1) that child splitter has advised a split, and 2)
// the compaction output is at the boundary between two user keys (also
// the boundary between atomic compaction units). Use this splitter to wrap
// any splitters that don't guarantee user key splits (i.e. splitters that make
// their determination in ways other than comparing the current key against a
// limit key.) If a wrapped splitter advises a split, it must continue
// to advise a split until a new output.
type userKeyChangeSplitter struct {
cmp Compare
splitter compactionOutputSplitter
unsafePrevUserKey func() []byte
}
func (u *userKeyChangeSplitter) shouldSplitBefore(key *InternalKey, tw *sstable.Writer) maybeSplit {
// NB: The userKeyChangeSplitter only needs to suffer a key comparison if
// the wrapped splitter requests a split.
//
// We could implement this splitter using frontiers: When the inner splitter
// requests a split before key `k`, we'd update a frontier to be
// ImmediateSuccessor(k). Then on the next key greater than >k, the
// frontier's `reached` func would be called and we'd return splitNow.
// This doesn't really save work since duplicate user keys are rare, and it
// requires us to materialize the ImmediateSuccessor key. It also prevents
// us from splitting on the same key that the inner splitter requested a
// split for—instead we need to wait until the next key. The current
// implementation uses `unsafePrevUserKey` to gain access to the previous
// key which allows it to immediately respect the inner splitter if
// possible.
if split := u.splitter.shouldSplitBefore(key, tw); split != splitNow {
return split
}
if u.cmp(key.UserKey, u.unsafePrevUserKey()) > 0 {
return splitNow
}
return noSplit
}
func (u *userKeyChangeSplitter) onNewOutput(key []byte) []byte {
return u.splitter.onNewOutput(key)
}
// compactionWritable is a objstorage.Writable wrapper that, on every write,
// updates a metric in `versions` on bytes written by in-progress compactions so
// far. It also increments a per-compaction `written` int.
type compactionWritable struct {
objstorage.Writable
versions *versionSet
written *int64
}
// Write is part of the objstorage.Writable interface.
func (c *compactionWritable) Write(p []byte) error {
if err := c.Writable.Write(p); err != nil {
return err
}
*c.written += int64(len(p))
c.versions.incrementCompactionBytes(int64(len(p)))
return nil
}
type compactionKind int
const (
compactionKindDefault compactionKind = iota
compactionKindFlush
// compactionKindMove denotes a move compaction where the input file is
// retained and linked in a new level without being obsoleted.
compactionKindMove
// compactionKindCopy denotes a copy compaction where the input file is
// copied byte-by-byte into a new file with a new FileNum in the output level.
compactionKindCopy
compactionKindDeleteOnly
compactionKindElisionOnly
compactionKindRead
compactionKindRewrite
compactionKindIngestedFlushable
)
func (k compactionKind) String() string {
switch k {
case compactionKindDefault:
return "default"
case compactionKindFlush:
return "flush"
case compactionKindMove:
return "move"
case compactionKindDeleteOnly:
return "delete-only"
case compactionKindElisionOnly:
return "elision-only"
case compactionKindRead:
return "read"
case compactionKindRewrite:
return "rewrite"
case compactionKindIngestedFlushable:
return "ingested-flushable"
case compactionKindCopy:
return "copy"
}
return "?"
}
// rangeKeyCompactionTransform is used to transform range key spans as part of the
// keyspan.MergingIter. As part of this transformation step, we can elide range
// keys in the last snapshot stripe, as well as coalesce range keys within
// snapshot stripes.
func rangeKeyCompactionTransform(
eq base.Equal, snapshots []uint64, elideRangeKey func(start, end []byte) bool,
) keyspan.Transformer {
return keyspan.TransformerFunc(func(cmp base.Compare, s keyspan.Span, dst *keyspan.Span) error {
elideInLastStripe := func(keys []keyspan.Key) []keyspan.Key {
// Unsets and deletes in the last snapshot stripe can be elided.
k := 0
for j := range keys {
if elideRangeKey(s.Start, s.End) &&
(keys[j].Kind() == InternalKeyKindRangeKeyUnset || keys[j].Kind() == InternalKeyKindRangeKeyDelete) {
continue
}
keys[k] = keys[j]
k++
}
keys = keys[:k]
return keys
}
// snapshots are in ascending order, while s.keys are in descending seqnum
// order. Partition s.keys by snapshot stripes, and call rangekey.Coalesce
// on each partition.
dst.Start = s.Start
dst.End = s.End
dst.Keys = dst.Keys[:0]
i, j := len(snapshots)-1, 0
usedLen := 0
for i >= 0 {
start := j
for j < len(s.Keys) && !base.Visible(s.Keys[j].SeqNum(), snapshots[i], base.InternalKeySeqNumMax) {
// Include j in current partition.
j++
}
if j > start {
keysDst := dst.Keys[usedLen:cap(dst.Keys)]
if err := rangekey.Coalesce(cmp, eq, s.Keys[start:j], &keysDst); err != nil {
return err
}
if j == len(s.Keys) {
// This is the last snapshot stripe. Unsets and deletes can be elided.
keysDst = elideInLastStripe(keysDst)
}
usedLen += len(keysDst)
dst.Keys = append(dst.Keys, keysDst...)
}
i--
}
if j < len(s.Keys) {
keysDst := dst.Keys[usedLen:cap(dst.Keys)]
if err := rangekey.Coalesce(cmp, eq, s.Keys[j:], &keysDst); err != nil {
return err
}
keysDst = elideInLastStripe(keysDst)
usedLen += len(keysDst)
dst.Keys = append(dst.Keys, keysDst...)
}
return nil
})
}
// compaction is a table compaction from one level to the next, starting from a
// given version.
type compaction struct {
// cancel is a bool that can be used by other goroutines to signal a compaction
// to cancel, such as if a conflicting excise operation raced it to manifest
// application. Only holders of the manifest lock will write to this atomic.
cancel atomic.Bool
kind compactionKind
cmp Compare
equal Equal
comparer *base.Comparer
formatKey base.FormatKey
logger Logger
version *version
stats base.InternalIteratorStats
beganAt time.Time
// versionEditApplied is set to true when a compaction has completed and the
// resulting version has been installed (if successful), but the compaction
// goroutine is still cleaning up (eg, deleting obsolete files).
versionEditApplied bool
bufferPool sstable.BufferPool
// startLevel is the level that is being compacted. Inputs from startLevel
// and outputLevel will be merged to produce a set of outputLevel files.
startLevel *compactionLevel
// outputLevel is the level that files are being produced in. outputLevel is
// equal to startLevel+1 except when:
// - if startLevel is 0, the output level equals compactionPicker.baseLevel().
// - in multilevel compaction, the output level is the lowest level involved in
// the compaction
// A compaction's outputLevel is nil for delete-only compactions.
outputLevel *compactionLevel
// extraLevels point to additional levels in between the input and output
// levels that get compacted in multilevel compactions
extraLevels []*compactionLevel
inputs []compactionLevel
// maxOutputFileSize is the maximum size of an individual table created
// during compaction.
maxOutputFileSize uint64
// maxOverlapBytes is the maximum number of bytes of overlap allowed for a
// single output table with the tables in the grandparent level.
maxOverlapBytes uint64
// disableSpanElision disables elision of range tombstones and range keys. Used
// by tests to allow range tombstones or range keys to be added to tables where
// they would otherwise be elided.
disableSpanElision bool
// flushing contains the flushables (aka memtables) that are being flushed.
flushing flushableList
// bytesIterated contains the number of bytes that have been flushed/compacted.
bytesIterated uint64
// bytesWritten contains the number of bytes that have been written to outputs.
bytesWritten int64
// The boundaries of the input data.
smallest InternalKey
largest InternalKey
// The range deletion tombstone fragmenter. Adds range tombstones as they are
// returned from `compactionIter` and fragments them for output to files.
// Referenced by `compactionIter` which uses it to check whether keys are deleted.
rangeDelFrag keyspan.Fragmenter
// The range key fragmenter. Similar to rangeDelFrag in that it gets range
// keys from the compaction iter and fragments them for output to files.
rangeKeyFrag keyspan.Fragmenter
// The range deletion tombstone iterator, that merges and fragments
// tombstones across levels. This iterator is included within the compaction
// input iterator as a single level.
// TODO(jackson): Remove this when the refactor of FragmentIterator,
// InterleavingIterator, etc is complete.
rangeDelIter keyspan.InternalIteratorShim
// rangeKeyInterleaving is the interleaving iter for range keys.
rangeKeyInterleaving keyspan.InterleavingIter
// A list of objects to close when the compaction finishes. Used by input
// iteration to keep rangeDelIters open for the lifetime of the compaction,
// and only close them when the compaction finishes.
closers []io.Closer
// grandparents are the tables in level+2 that overlap with the files being
// compacted. Used to determine output table boundaries. Do not assume that the actual files
// in the grandparent when this compaction finishes will be the same.
grandparents manifest.LevelSlice
// Boundaries at which flushes to L0 should be split. Determined by
// L0Sublevels. If nil, flushes aren't split.
l0Limits [][]byte
// List of disjoint inuse key ranges the compaction overlaps with in
// grandparent and lower levels. See setupInuseKeyRanges() for the
// construction. Used by elideTombstone() and elideRangeTombstone() to
// determine if keys affected by a tombstone possibly exist at a lower level.
inuseKeyRanges []manifest.UserKeyRange
// inuseEntireRange is set if the above inuse key ranges wholly contain the
// compaction's key range. This allows compactions in higher levels to often
// elide key comparisons.
inuseEntireRange bool
elideTombstoneIndex int
// allowedZeroSeqNum is true if seqnums can be zeroed if there are no
// snapshots requiring them to be kept. This determination is made by
// looking for an sstable which overlaps the bounds of the compaction at a
// lower level in the LSM during runCompaction.
allowedZeroSeqNum bool
metrics map[int]*LevelMetrics
pickerMetrics compactionPickerMetrics
}
func (c *compaction) makeInfo(jobID int) CompactionInfo {
info := CompactionInfo{
JobID: jobID,
Reason: c.kind.String(),
Input: make([]LevelInfo, 0, len(c.inputs)),
Annotations: []string{},
}
for _, cl := range c.inputs {
inputInfo := LevelInfo{Level: cl.level, Tables: nil}
iter := cl.files.Iter()
for m := iter.First(); m != nil; m = iter.Next() {
inputInfo.Tables = append(inputInfo.Tables, m.TableInfo())
}
info.Input = append(info.Input, inputInfo)
}
if c.outputLevel != nil {
info.Output.Level = c.outputLevel.level
// If there are no inputs from the output level (eg, a move
// compaction), add an empty LevelInfo to info.Input.
if len(c.inputs) > 0 && c.inputs[len(c.inputs)-1].level != c.outputLevel.level {
info.Input = append(info.Input, LevelInfo{Level: c.outputLevel.level})
}
} else {
// For a delete-only compaction, set the output level to L6. The
// output level is not meaningful here, but complicating the
// info.Output interface with a pointer doesn't seem worth the
// semantic distinction.
info.Output.Level = numLevels - 1
}
for i, score := range c.pickerMetrics.scores {
info.Input[i].Score = score
}
info.SingleLevelOverlappingRatio = c.pickerMetrics.singleLevelOverlappingRatio
info.MultiLevelOverlappingRatio = c.pickerMetrics.multiLevelOverlappingRatio
if len(info.Input) > 2 {
info.Annotations = append(info.Annotations, "multilevel")
}
return info
}
func newCompaction(
pc *pickedCompaction, opts *Options, beganAt time.Time, provider objstorage.Provider,
) *compaction {
c := &compaction{
kind: compactionKindDefault,
cmp: pc.cmp,
equal: opts.equal(),
comparer: opts.Comparer,
formatKey: opts.Comparer.FormatKey,
inputs: pc.inputs,
smallest: pc.smallest,
largest: pc.largest,
logger: opts.Logger,
version: pc.version,
beganAt: beganAt,
maxOutputFileSize: pc.maxOutputFileSize,
maxOverlapBytes: pc.maxOverlapBytes,
pickerMetrics: pc.pickerMetrics,
}
c.startLevel = &c.inputs[0]
if pc.startLevel.l0SublevelInfo != nil {
c.startLevel.l0SublevelInfo = pc.startLevel.l0SublevelInfo
}
c.outputLevel = &c.inputs[1]
if len(pc.extraLevels) > 0 {
c.extraLevels = pc.extraLevels
c.outputLevel = &c.inputs[len(c.inputs)-1]
}
// Compute the set of outputLevel+1 files that overlap this compaction (these
// are the grandparent sstables).
if c.outputLevel.level+1 < numLevels {
c.grandparents = c.version.Overlaps(c.outputLevel.level+1, c.cmp,
c.smallest.UserKey, c.largest.UserKey, c.largest.IsExclusiveSentinel())
}
c.setupInuseKeyRanges()
c.kind = pc.kind
if c.kind == compactionKindDefault && c.outputLevel.files.Empty() && !c.hasExtraLevelData() &&
c.startLevel.files.Len() == 1 && c.grandparents.SizeSum() <= c.maxOverlapBytes {
// This compaction can be converted into a move or copy from one level
// to the next. We avoid such a move if there is lots of overlapping
// grandparent data. Otherwise, the move could create a parent file
// that will require a very expensive merge later on.
iter := c.startLevel.files.Iter()
meta := iter.First()
isRemote := false
// We should always be passed a provider, except in some unit tests.
if provider != nil {
objMeta, err := provider.Lookup(fileTypeTable, meta.FileBacking.DiskFileNum)
if err != nil {
panic(errors.Wrapf(err, "cannot lookup table %s in provider", meta.FileBacking.DiskFileNum))
}
isRemote = objMeta.IsRemote()
}
// Avoid a trivial move or copy if all of these are true, as rewriting a
// new file is better:
//
// 1) The source file is a virtual sstable
// 2) The existing file `meta` is on non-remote storage
// 3) The output level prefers shared storage
mustCopy := !isRemote && remote.ShouldCreateShared(opts.Experimental.CreateOnShared, c.outputLevel.level)
if mustCopy {
// If the source is virtual, it's best to just rewrite the file as all
// conditions in the above comment are met.
if !meta.Virtual {
c.kind = compactionKindCopy
}
} else {
c.kind = compactionKindMove
}
}
return c
}
func newDeleteOnlyCompaction(
opts *Options, cur *version, inputs []compactionLevel, beganAt time.Time,
) *compaction {
c := &compaction{
kind: compactionKindDeleteOnly,
cmp: opts.Comparer.Compare,
equal: opts.equal(),
comparer: opts.Comparer,
formatKey: opts.Comparer.FormatKey,
logger: opts.Logger,
version: cur,
beganAt: beganAt,
inputs: inputs,
}
// Set c.smallest, c.largest.
files := make([]manifest.LevelIterator, 0, len(inputs))
for _, in := range inputs {
files = append(files, in.files.Iter())
}
c.smallest, c.largest = manifest.KeyRange(opts.Comparer.Compare, files...)
return c
}
func adjustGrandparentOverlapBytesForFlush(c *compaction, flushingBytes uint64) {
// Heuristic to place a lower bound on compaction output file size
// caused by Lbase. Prior to this heuristic we have observed an L0 in
// production with 310K files of which 290K files were < 10KB in size.
// Our hypothesis is that it was caused by L1 having 2600 files and
// ~10GB, such that each flush got split into many tiny files due to
// overlapping with most of the files in Lbase.
//
// The computation below is general in that it accounts
// for flushing different volumes of data (e.g. we may be flushing
// many memtables). For illustration, we consider the typical
// example of flushing a 64MB memtable. So 12.8MB output,
// based on the compression guess below. If the compressed bytes
// guess is an over-estimate we will end up with smaller files,
// and if an under-estimate we will end up with larger files.
// With a 2MB target file size, 7 files. We are willing to accept
// 4x the number of files, if it results in better write amplification
// when later compacting to Lbase, i.e., ~450KB files (target file
// size / 4).
//
// Note that this is a pessimistic heuristic in that
// fileCountUpperBoundDueToGrandparents could be far from the actual
// number of files produced due to the grandparent limits. For
// example, in the extreme, consider a flush that overlaps with 1000
// files in Lbase f0...f999, and the initially calculated value of
// maxOverlapBytes will cause splits at f10, f20,..., f990, which
// means an upper bound file count of 100 files. Say the input bytes
// in the flush are such that acceptableFileCount=10. We will fatten
// up maxOverlapBytes by 10x to ensure that the upper bound file count
// drops to 10. However, it is possible that in practice, even without
// this change, we would have produced no more than 10 files, and that
// this change makes the files unnecessarily wide. Say the input bytes
// are distributed such that 10% are in f0...f9, 10% in f10...f19, ...
// 10% in f80...f89 and 10% in f990...f999. The original value of
// maxOverlapBytes would have actually produced only 10 sstables. But
// by increasing maxOverlapBytes by 10x, we may produce 1 sstable that
// spans f0...f89, i.e., a much wider sstable than necessary.
//
// We could produce a tighter estimate of
// fileCountUpperBoundDueToGrandparents if we had knowledge of the key
// distribution of the flush. The 4x multiplier mentioned earlier is
// a way to try to compensate for this pessimism.
//
// TODO(sumeer): we don't have compression info for the data being
// flushed, but it is likely that existing files that overlap with
// this flush in Lbase are representative wrt compression ratio. We
// could store the uncompressed size in FileMetadata and estimate
// the compression ratio.
const approxCompressionRatio = 0.2
approxOutputBytes := approxCompressionRatio * float64(flushingBytes)
approxNumFilesBasedOnTargetSize :=
int(math.Ceil(approxOutputBytes / float64(c.maxOutputFileSize)))
acceptableFileCount := float64(4 * approxNumFilesBasedOnTargetSize)
// The byte calculation is linear in numGrandparentFiles, but we will
// incur this linear cost in findGrandparentLimit too, so we are also
// willing to pay it now. We could approximate this cheaply by using
// the mean file size of Lbase.
grandparentFileBytes := c.grandparents.SizeSum()
fileCountUpperBoundDueToGrandparents :=
float64(grandparentFileBytes) / float64(c.maxOverlapBytes)
if fileCountUpperBoundDueToGrandparents > acceptableFileCount {
c.maxOverlapBytes = uint64(
float64(c.maxOverlapBytes) *
(fileCountUpperBoundDueToGrandparents / acceptableFileCount))
}
}
func newFlush(
opts *Options, cur *version, baseLevel int, flushing flushableList, beganAt time.Time,
) *compaction {
c := &compaction{
kind: compactionKindFlush,
cmp: opts.Comparer.Compare,
equal: opts.equal(),
comparer: opts.Comparer,
formatKey: opts.Comparer.FormatKey,
logger: opts.Logger,
version: cur,
beganAt: beganAt,
inputs: []compactionLevel{{level: -1}, {level: 0}},
maxOutputFileSize: math.MaxUint64,
maxOverlapBytes: math.MaxUint64,
flushing: flushing,
}
c.startLevel = &c.inputs[0]
c.outputLevel = &c.inputs[1]
if len(flushing) > 0 {
if _, ok := flushing[0].flushable.(*ingestedFlushable); ok {
if len(flushing) != 1 {
panic("pebble: ingestedFlushable must be flushed one at a time.")
}
c.kind = compactionKindIngestedFlushable
return c
}
}
// Make sure there's no ingestedFlushable after the first flushable in the
// list.
for _, f := range flushing {
if _, ok := f.flushable.(*ingestedFlushable); ok {
panic("pebble: flushing shouldn't contain ingestedFlushable flushable")
}
}
if cur.L0Sublevels != nil {
c.l0Limits = cur.L0Sublevels.FlushSplitKeys()
}
smallestSet, largestSet := false, false
updatePointBounds := func(iter internalIterator) {
if key, _ := iter.First(); key != nil {
if !smallestSet ||
base.InternalCompare(c.cmp, c.smallest, *key) > 0 {
smallestSet = true
c.smallest = key.Clone()
}
}
if key, _ := iter.Last(); key != nil {
if !largestSet ||
base.InternalCompare(c.cmp, c.largest, *key) < 0 {
largestSet = true
c.largest = key.Clone()
}
}
}
updateRangeBounds := func(iter keyspan.FragmentIterator) {
// File bounds require s != nil && !s.Empty(). We only need to check for
// s != nil here, as the memtable's FragmentIterator would never surface
// empty spans.
if s := iter.First(); s != nil {
if key := s.SmallestKey(); !smallestSet ||
base.InternalCompare(c.cmp, c.smallest, key) > 0 {
smallestSet = true
c.smallest = key.Clone()
}
}
if s := iter.Last(); s != nil {
if key := s.LargestKey(); !largestSet ||
base.InternalCompare(c.cmp, c.largest, key) < 0 {
largestSet = true
c.largest = key.Clone()
}
}
}
var flushingBytes uint64
for i := range flushing {
f := flushing[i]
updatePointBounds(f.newIter(nil))
if rangeDelIter := f.newRangeDelIter(nil); rangeDelIter != nil {
updateRangeBounds(rangeDelIter)
}
if rangeKeyIter := f.newRangeKeyIter(nil); rangeKeyIter != nil {
updateRangeBounds(rangeKeyIter)
}
flushingBytes += f.inuseBytes()
}
if opts.FlushSplitBytes > 0 {
c.maxOutputFileSize = uint64(opts.Level(0).TargetFileSize)
c.maxOverlapBytes = maxGrandparentOverlapBytes(opts, 0)
c.grandparents = c.version.Overlaps(baseLevel, c.cmp, c.smallest.UserKey,
c.largest.UserKey, c.largest.IsExclusiveSentinel())
adjustGrandparentOverlapBytesForFlush(c, flushingBytes)
}
c.setupInuseKeyRanges()
return c
}
func (c *compaction) hasExtraLevelData() bool {
if len(c.extraLevels) == 0 {
// not a multi level compaction
return false
} else if c.extraLevels[0].files.Empty() {
// a multi level compaction without data in the intermediate input level;
// e.g. for a multi level compaction with levels 4,5, and 6, this could
// occur if there is no files to compact in 5, or in 5 and 6 (i.e. a move).
return false
}
return true
}
func (c *compaction) setupInuseKeyRanges() {
level := c.outputLevel.level + 1
if c.outputLevel.level == 0 {
level = 0
}
// calculateInuseKeyRanges will return a series of sorted spans. Overlapping
// or abutting spans have already been merged.
c.inuseKeyRanges = calculateInuseKeyRanges(
c.version, c.cmp, level, numLevels-1, c.smallest.UserKey, c.largest.UserKey,
)
// Check if there's a single in-use span that encompasses the entire key
// range of the compaction. This is an optimization to avoid key comparisons
// against inuseKeyRanges during the compaction when every key within the
// compaction overlaps with an in-use span.
if len(c.inuseKeyRanges) > 0 {
c.inuseEntireRange = c.cmp(c.inuseKeyRanges[0].Start, c.smallest.UserKey) <= 0 &&
c.cmp(c.inuseKeyRanges[0].End, c.largest.UserKey) >= 0
}
}
func calculateInuseKeyRanges(
v *version, cmp base.Compare, level, maxLevel int, smallest, largest []byte,
) []manifest.UserKeyRange {
// Use two slices, alternating which one is input and which one is output
// as we descend the LSM.
var input, output []manifest.UserKeyRange
// L0 requires special treatment, since sstables within L0 may overlap.
// We use the L0 Sublevels structure to efficiently calculate the merged
// in-use key ranges.
if level == 0 {
output = v.L0Sublevels.InUseKeyRanges(smallest, largest)
level++
}
for ; level <= maxLevel; level++ {
// NB: We always treat `largest` as inclusive for simplicity, because
// there's little consequence to calculating slightly broader in-use key
// ranges.
overlaps := v.Overlaps(level, cmp, smallest, largest, false /* exclusiveEnd */)
iter := overlaps.Iter()
// We may already have in-use key ranges from higher levels. Iterate
// through both our accumulated in-use key ranges and this level's
// files, merging the two.
//
// Tables higher within the LSM have broader key spaces. We use this
// when possible to seek past a level's files that are contained by
// our current accumulated in-use key ranges. This helps avoid
// per-sstable work during flushes or compactions in high levels which
// overlap the majority of the LSM's sstables.
input, output = output, input
output = output[:0]
var currFile *fileMetadata
var currAccum *manifest.UserKeyRange
if len(input) > 0 {
currAccum, input = &input[0], input[1:]
}
// If we have an accumulated key range and its start is ≤ smallest,
// we can seek to the accumulated range's end. Otherwise, we need to
// start at the first overlapping file within the level.
if currAccum != nil && cmp(currAccum.Start, smallest) <= 0 {
currFile = seekGT(&iter, cmp, currAccum.End)
} else {
currFile = iter.First()
}
for currFile != nil || currAccum != nil {
// If we've exhausted either the files in the level or the
// accumulated key ranges, we just need to append the one we have.
// If we have both a currFile and a currAccum, they either overlap
// or they're disjoint. If they're disjoint, we append whichever
// one sorts first and move on to the next file or range. If they
// overlap, we merge them into currAccum and proceed to the next
// file.
switch {
case currAccum == nil || (currFile != nil && cmp(currFile.Largest.UserKey, currAccum.Start) < 0):
// This file is strictly before the current accumulated range,
// or there are no more accumulated ranges.
output = append(output, manifest.UserKeyRange{
Start: currFile.Smallest.UserKey,
End: currFile.Largest.UserKey,
})
currFile = iter.Next()
case currFile == nil || (currAccum != nil && cmp(currAccum.End, currFile.Smallest.UserKey) < 0):
// The current accumulated key range is strictly before the
// current file, or there are no more files.
output = append(output, *currAccum)
currAccum = nil
if len(input) > 0 {
currAccum, input = &input[0], input[1:]
}
default:
// The current accumulated range and the current file overlap.
// Adjust the accumulated range to be the union.
if cmp(currFile.Smallest.UserKey, currAccum.Start) < 0 {
currAccum.Start = currFile.Smallest.UserKey
}
if cmp(currFile.Largest.UserKey, currAccum.End) > 0 {
currAccum.End = currFile.Largest.UserKey
}
// Extending `currAccum`'s end boundary may have caused it to
// overlap with `input` key ranges that we haven't processed
// yet. Merge any such key ranges.
for len(input) > 0 && cmp(input[0].Start, currAccum.End) <= 0 {
if cmp(input[0].End, currAccum.End) > 0 {
currAccum.End = input[0].End
}
input = input[1:]
}
// Seek the level iterator past our current accumulated end.
currFile = seekGT(&iter, cmp, currAccum.End)
}
}
}
return output
}
func seekGT(iter *manifest.LevelIterator, cmp base.Compare, key []byte) *manifest.FileMetadata {
f := iter.SeekGE(cmp, key)
for f != nil && cmp(f.Largest.UserKey, key) == 0 {
f = iter.Next()
}
return f
}
// findGrandparentLimit takes the start user key for a table and returns the
// user key to which that table can extend without excessively overlapping
// the grandparent level. If no limit is needed considering the grandparent
// files, this function returns nil. This is done in order to prevent a table
// at level N from overlapping too much data at level N+1. We want to avoid
// such large overlaps because they translate into large compactions. The
// current heuristic stops output of a table if the addition of another key
// would cause the table to overlap more than 10x the target file size at
// level N. See maxGrandparentOverlapBytes.
func (c *compaction) findGrandparentLimit(start []byte) []byte {
iter := c.grandparents.Iter()
var overlappedBytes uint64
var greater bool
for f := iter.SeekGE(c.cmp, start); f != nil; f = iter.Next() {
overlappedBytes += f.Size
// To ensure forward progress we always return a larger user
// key than where we started. See comments above clients of
// this function for how this is used.
greater = greater || c.cmp(f.Smallest.UserKey, start) > 0
if !greater {
continue
}
// We return the smallest bound of a sstable rather than the
// largest because the smallest is always inclusive, and limits
// are used exlusively when truncating range tombstones. If we
// truncated an output to the largest key while there's a
// pending tombstone, the next output file would also overlap
// the same grandparent f.
if overlappedBytes > c.maxOverlapBytes {
return f.Smallest.UserKey
}
}
return nil
}
// findL0Limit takes the start key for a table and returns the user key to which
// that table can be extended without hitting the next l0Limit. Having flushed
// sstables "bridging across" an l0Limit could lead to increased L0 -> LBase
// compaction sizes as well as elevated read amplification.
func (c *compaction) findL0Limit(start []byte) []byte {
if c.startLevel.level > -1 || c.outputLevel.level != 0 || len(c.l0Limits) == 0 {
return nil
}
index := sort.Search(len(c.l0Limits), func(i int) bool {
return c.cmp(c.l0Limits[i], start) > 0
})
if index < len(c.l0Limits) {
return c.l0Limits[index]
}
return nil
}
// errorOnUserKeyOverlap returns an error if the last two written sstables in
// this compaction have revisions of the same user key present in both sstables,
// when it shouldn't (eg. when splitting flushes).
func (c *compaction) errorOnUserKeyOverlap(ve *versionEdit) error {
if n := len(ve.NewFiles); n > 1 {
meta := ve.NewFiles[n-1].Meta
prevMeta := ve.NewFiles[n-2].Meta
if !prevMeta.Largest.IsExclusiveSentinel() &&
c.cmp(prevMeta.Largest.UserKey, meta.Smallest.UserKey) >= 0 {
return errors.Errorf("pebble: compaction split user key across two sstables: %s in %s and %s",
prevMeta.Largest.Pretty(c.formatKey),
prevMeta.FileNum,
meta.FileNum)
}
}
return nil
}
// allowZeroSeqNum returns true if seqnum's can be zeroed if there are no
// snapshots requiring them to be kept. It performs this determination by
// looking for an sstable which overlaps the bounds of the compaction at a
// lower level in the LSM.
func (c *compaction) allowZeroSeqNum() bool {
return c.elideRangeTombstone(c.smallest.UserKey, c.largest.UserKey)
}
// elideTombstone returns true if it is ok to elide a tombstone for the
// specified key. A return value of true guarantees that there are no key/value
// pairs at c.level+2 or higher that possibly contain the specified user
// key. The keys in multiple invocations to elideTombstone must be supplied in
// order.
func (c *compaction) elideTombstone(key []byte) bool {
if c.inuseEntireRange || len(c.flushing) != 0 {
return false
}
for ; c.elideTombstoneIndex < len(c.inuseKeyRanges); c.elideTombstoneIndex++ {
r := &c.inuseKeyRanges[c.elideTombstoneIndex]
if c.cmp(key, r.End) <= 0 {
if c.cmp(key, r.Start) >= 0 {
return false
}
break
}
}
return true
}
// elideRangeTombstone returns true if it is ok to elide the specified range
// tombstone. A return value of true guarantees that there are no key/value
// pairs at c.outputLevel.level+1 or higher that possibly overlap the specified
// tombstone.
func (c *compaction) elideRangeTombstone(start, end []byte) bool {
// Disable range tombstone elision if the testing knob for that is enabled,
// or if we are flushing memtables. The latter requirement is due to
// inuseKeyRanges not accounting for key ranges in other memtables that are
// being flushed in the same compaction. It's possible for a range tombstone
// in one memtable to overlap keys in a preceding memtable in c.flushing.
//
// This function is also used in setting allowZeroSeqNum, so disabling
// elision of range tombstones also disables zeroing of SeqNums.
//
// TODO(peter): we disable zeroing of seqnums during flushing to match
// RocksDB behavior and to avoid generating overlapping sstables during
// DB.replayWAL. When replaying WAL files at startup, we flush after each
// WAL is replayed building up a single version edit that is
// applied. Because we don't apply the version edit after each flush, this
// code doesn't know that L0 contains files and zeroing of seqnums should
// be disabled. That is fixable, but it seems safer to just match the
// RocksDB behavior for now.
if c.disableSpanElision || len(c.flushing) != 0 {
return false
}
lower := sort.Search(len(c.inuseKeyRanges), func(i int) bool {
return c.cmp(c.inuseKeyRanges[i].End, start) >= 0
})
upper := sort.Search(len(c.inuseKeyRanges), func(i int) bool {
return c.cmp(c.inuseKeyRanges[i].Start, end) > 0
})
return lower >= upper
}
// elideRangeKey returns true if it is ok to elide the specified range key. A
// return value of true guarantees that there are no key/value pairs at
// c.outputLevel.level+1 or higher that possibly overlap the specified range key.
func (c *compaction) elideRangeKey(start, end []byte) bool {
// TODO(bilal): Track inuseKeyRanges separately for the range keyspace as
// opposed to the point keyspace. Once that is done, elideRangeTombstone
// can just check in the point keyspace, and this function can check for
// inuseKeyRanges in the range keyspace.
return c.elideRangeTombstone(start, end)
}
// newInputIter returns an iterator over all the input tables in a compaction.
func (c *compaction) newInputIter(
newIters tableNewIters, newRangeKeyIter keyspan.TableNewSpanIter, snapshots []uint64,
) (_ internalIterator, retErr error) {
// Validate the ordering of compaction input files for defense in depth.
// TODO(jackson): Some of the CheckOrdering calls may be adapted to pass
// ProhibitSplitUserKeys if we thread the active format major version in. Or
// if we remove support for earlier FMVs, we can remove the parameter
// altogether.
if len(c.flushing) == 0 {
if c.startLevel.level >= 0 {
err := manifest.CheckOrdering(c.cmp, c.formatKey,
manifest.Level(c.startLevel.level), c.startLevel.files.Iter(),
manifest.AllowSplitUserKeys)
if err != nil {
return nil, err
}
}
err := manifest.CheckOrdering(c.cmp, c.formatKey,
manifest.Level(c.outputLevel.level), c.outputLevel.files.Iter(),
manifest.AllowSplitUserKeys)
if err != nil {
return nil, err
}
if c.startLevel.level == 0 {
if c.startLevel.l0SublevelInfo == nil {
panic("l0SublevelInfo not created for compaction out of L0")
}
for _, info := range c.startLevel.l0SublevelInfo {
err := manifest.CheckOrdering(c.cmp, c.formatKey,
info.sublevel, info.Iter(),
// NB: L0 sublevels have never allowed split user keys.
manifest.ProhibitSplitUserKeys)
if err != nil {
return nil, err
}
}
}
if len(c.extraLevels) > 0 {
if len(c.extraLevels) > 1 {
panic("n>2 multi level compaction not implemented yet")
}
interLevel := c.extraLevels[0]
err := manifest.CheckOrdering(c.cmp, c.formatKey,
manifest.Level(interLevel.level), interLevel.files.Iter(),
manifest.AllowSplitUserKeys)
if err != nil {
return nil, err
}
}
}
// There are three classes of keys that a compaction needs to process: point
// keys, range deletion tombstones and range keys. Collect all iterators for
// all these classes of keys from all the levels. We'll aggregate them
// together farther below.
//
// numInputLevels is an approximation of the number of iterator levels. Due
// to idiosyncrasies in iterator construction, we may (rarely) exceed this
// initial capacity.
numInputLevels := len(c.flushing)
if numInputLevels < len(c.inputs) {
numInputLevels = len(c.inputs)
}
iters := make([]internalIterator, 0, numInputLevels)
rangeDelIters := make([]keyspan.FragmentIterator, 0, numInputLevels)
rangeKeyIters := make([]keyspan.FragmentIterator, 0, numInputLevels)
// If construction of the iterator inputs fails, ensure that we close all
// the consitutent iterators.
defer func() {
if retErr != nil {
for _, iter := range iters {
if iter != nil {
iter.Close()
}
}
for _, rangeDelIter := range rangeDelIters {
rangeDelIter.Close()
}
}
}()
iterOpts := IterOptions{
CategoryAndQoS: sstable.CategoryAndQoS{
Category: "pebble-compaction",
QoSLevel: sstable.NonLatencySensitiveQoSLevel,
},
logger: c.logger,
}
// Populate iters, rangeDelIters and rangeKeyIters with the appropriate
// constituent iterators. This depends on whether this is a flush or a
// compaction.
if len(c.flushing) != 0 {
// If flushing, we need to build the input iterators over the memtables
// stored in c.flushing.
for i := range c.flushing {
f := c.flushing[i]
iters = append(iters, f.newFlushIter(nil, &c.bytesIterated))
rangeDelIter := f.newRangeDelIter(nil)
if rangeDelIter != nil {
rangeDelIters = append(rangeDelIters, rangeDelIter)
}
if rangeKeyIter := f.newRangeKeyIter(nil); rangeKeyIter != nil {
rangeKeyIters = append(rangeKeyIters, rangeKeyIter)
}
}
} else {
addItersForLevel := func(level *compactionLevel, l manifest.Level) error {
// Add a *levelIter for point iterators. Because we don't call
// initRangeDel, the levelIter will close and forget the range
// deletion iterator when it steps on to a new file. Surfacing range
// deletions to compactions are handled below.
iters = append(iters, newLevelIter(context.Background(),
iterOpts, c.comparer, newIters, level.files.Iter(), l, internalIterOpts{
bytesIterated: &c.bytesIterated,
bufferPool: &c.bufferPool,
}))
// TODO(jackson): Use keyspan.LevelIter to avoid loading all the range
// deletions into memory upfront. (See #2015, which reverted this.)
// There will be no user keys that are split between sstables
// within a level in Cockroach 23.1, which unblocks this optimization.
// Add the range deletion iterator for each file as an independent level
// in mergingIter, as opposed to making a levelIter out of those. This
// is safer as levelIter expects all keys coming from underlying
// iterators to be in order. Due to compaction / tombstone writing
// logic in finishOutput(), it is possible for range tombstones to not
// be strictly ordered across all files in one level.
//
// Consider this example from the metamorphic tests (also repeated in
// finishOutput()), consisting of three L3 files with their bounds
// specified in square brackets next to the file name:
//
// ./000240.sst [tmgc#391,MERGE-tmgc#391,MERGE]
// tmgc#391,MERGE [786e627a]
// tmgc-udkatvs#331,RANGEDEL
//
// ./000241.sst [tmgc#384,MERGE-tmgc#384,MERGE]
// tmgc#384,MERGE [666c7070]
// tmgc-tvsalezade#383,RANGEDEL
// tmgc-tvsalezade#331,RANGEDEL
//
// ./000242.sst [tmgc#383,RANGEDEL-tvsalezade#72057594037927935,RANGEDEL]
// tmgc-tvsalezade#383,RANGEDEL
// tmgc#375,SET [72646c78766965616c72776865676e79]
// tmgc-tvsalezade#356,RANGEDEL
//
// Here, the range tombstone in 000240.sst falls "after" one in
// 000241.sst, despite 000240.sst being ordered "before" 000241.sst for
// levelIter's purposes. While each file is still consistent before its
// bounds, it's safer to have all rangedel iterators be visible to
// mergingIter.
iter := level.files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
rangeDelIter, closer, err := c.newRangeDelIter(
newIters, iter.Take(), iterOpts, l, &c.bytesIterated)
if err != nil {
// The error will already be annotated with the BackingFileNum, so
// we annotate it with the FileNum.
return errors.Wrapf(err, "pebble: could not open table %s", errors.Safe(f.FileNum))
}
if rangeDelIter == nil {
continue
}
rangeDelIters = append(rangeDelIters, rangeDelIter)
c.closers = append(c.closers, closer)
}
// Check if this level has any range keys.
hasRangeKeys := false
for f := iter.First(); f != nil; f = iter.Next() {
if f.HasRangeKeys {
hasRangeKeys = true
break
}
}
if hasRangeKeys {
li := &keyspan.LevelIter{}
newRangeKeyIterWrapper := func(file *manifest.FileMetadata, iterOptions keyspan.SpanIterOptions) (keyspan.FragmentIterator, error) {
iter, err := newRangeKeyIter(file, iterOptions)
if err != nil {
return nil, err
} else if iter == nil {
return emptyKeyspanIter, nil
}
// Ensure that the range key iter is not closed until the compaction is
// finished. This is necessary because range key processing
// requires the range keys to be held in memory for up to the
// lifetime of the compaction.
c.closers = append(c.closers, iter)
iter = noCloseIter{iter}
// We do not need to truncate range keys to sstable boundaries, or
// only read within the file's atomic compaction units, unlike with
// range tombstones. This is because range keys were added after we
// stopped splitting user keys across sstables, so all the range keys
// in this sstable must wholly lie within the file's bounds.
return iter, err
}
li.Init(keyspan.SpanIterOptions{}, c.cmp, newRangeKeyIterWrapper, level.files.Iter(), l, manifest.KeyTypeRange)
rangeKeyIters = append(rangeKeyIters, li)
}
return nil
}
for i := range c.inputs {
// If the level is annotated with l0SublevelInfo, expand it into one
// level per sublevel.
// TODO(jackson): Perform this expansion even earlier when we pick the
// compaction?
if len(c.inputs[i].l0SublevelInfo) > 0 {
for _, info := range c.startLevel.l0SublevelInfo {
sublevelCompactionLevel := &compactionLevel{0, info.LevelSlice, nil}
if err := addItersForLevel(sublevelCompactionLevel, info.sublevel); err != nil {
return nil, err
}
}
continue
}
if err := addItersForLevel(&c.inputs[i], manifest.Level(c.inputs[i].level)); err != nil {
return nil, err
}
}
}
// In normal operation, levelIter iterates over the point operations in a
// level, and initializes a rangeDelIter pointer for the range deletions in
// each table. During compaction, we want to iterate over the merged view of
// point operations and range deletions. In order to do this we create one
// levelIter per level to iterate over the point operations, and collect up
// all the range deletion files.
//
// The range deletion levels are first combined with a keyspan.MergingIter
// (currently wrapped by a keyspan.InternalIteratorShim to satisfy the
// internal iterator interface). The resulting merged rangedel iterator is
// then included with the point levels in a single mergingIter.
//
// Combine all the rangedel iterators using a keyspan.MergingIterator and a
// InternalIteratorShim so that the range deletions may be interleaved in
// the compaction input.
// TODO(jackson): Replace the InternalIteratorShim with an interleaving
// iterator.
if len(rangeDelIters) > 0 {
c.rangeDelIter.Init(c.cmp, rangeDelIters...)
iters = append(iters, &c.rangeDelIter)
}
// If there's only one constituent point iterator, we can avoid the overhead
// of a *mergingIter. This is possible, for example, when performing a flush
// of a single memtable. Otherwise, combine all the iterators into a merging
// iter.
iter := iters[0]
if len(iters) > 0 {
iter = newMergingIter(c.logger, &c.stats, c.cmp, nil, iters...)
}
// If there are range key iterators, we need to combine them using
// keyspan.MergingIter, and then interleave them among the points.
if len(rangeKeyIters) > 0 {
mi := &keyspan.MergingIter{}
mi.Init(c.cmp, rangeKeyCompactionTransform(c.equal, snapshots, c.elideRangeKey), new(keyspan.MergingBuffers), rangeKeyIters...)
di := &keyspan.DefragmentingIter{}
di.Init(c.comparer, mi, keyspan.DefragmentInternal, keyspan.StaticDefragmentReducer, new(keyspan.DefragmentingBuffers))
c.rangeKeyInterleaving.Init(c.comparer, iter, di, keyspan.InterleavingIterOpts{})
iter = &c.rangeKeyInterleaving
}
return iter, nil
}
func (c *compaction) newRangeDelIter(
newIters tableNewIters,
f manifest.LevelFile,
opts IterOptions,
l manifest.Level,
bytesIterated *uint64,
) (keyspan.FragmentIterator, io.Closer, error) {
opts.level = l
iter, rangeDelIter, err := newIters(context.Background(), f.FileMetadata,
&opts, internalIterOpts{
bytesIterated: &c.bytesIterated,
bufferPool: &c.bufferPool,
})
if err != nil {
return nil, nil, err
}
// TODO(peter): It is mildly wasteful to open the point iterator only to
// immediately close it. One way to solve this would be to add new
// methods to tableCache for creating point and range-deletion iterators
// independently. We'd only want to use those methods here,
// though. Doesn't seem worth the hassle in the near term.
if err = iter.Close(); err != nil {
if rangeDelIter != nil {
err = errors.CombineErrors(err, rangeDelIter.Close())
}
return nil, nil, err
}
if rangeDelIter == nil {
// The file doesn't contain any range deletions.
return nil, nil, nil
}
// Ensure that rangeDelIter is not closed until the compaction is
// finished. This is necessary because range tombstone processing
// requires the range tombstones to be held in memory for up to the
// lifetime of the compaction.
closer := rangeDelIter
rangeDelIter = noCloseIter{rangeDelIter}
// Truncate the range tombstones returned by the iterator to the
// upper bound of the atomic compaction unit of the file. We want to
// truncate the range tombstone to the bounds of the file, but files
// with split user keys pose an obstacle: The file's largest bound
// is inclusive whereas the range tombstone's end is exclusive.
//
// Consider the example:
//
// 000001:[b-f#200] range del [c,k)
// 000002:[f#190-g#inf] range del [c,k)
// 000003:[g#500-i#3]
//
// Files 000001 and 000002 contain the untruncated range tombstones
// [c,k). While the keyspace covered by 000003 was at one point
// deleted by the tombstone [c,k), the tombstone may have already
// been compacted away and the file does not contain an untruncated
// range tombstone. We want to bound 000001's tombstone to the file
// bounds, but it's not possible to encode a range tombstone with an
// end boundary within a user key (eg, between sequence numbers
// f#200 and f#190). Instead, we expand 000001 to its atomic
// compaction unit (000001 and 000002) and truncate the tombstone to
// g#inf.
//
// NB: We must not use the atomic compaction unit of the entire
// compaction, because the [c,k) tombstone contained in the file
// 000001 ≥ g. If 000001, 000002 and 000003 are all included in the
// same compaction, the compaction's atomic compaction unit includes
// 000003. However 000003's keys must not be covered by 000001's
// untruncated range tombstone.
//
// Note that we need do this truncation at read time in order to
// handle sstables generated by RocksDB and earlier versions of
// Pebble which do not truncate range tombstones to atomic
// compaction unit boundaries at write time.
//
// The current Pebble compaction logic DOES truncate tombstones to
// atomic unit boundaries at compaction time too.
atomicUnit, _ := expandToAtomicUnit(c.cmp, f.Slice(), true /* disableIsCompacting */)
lowerBound, upperBound := manifest.KeyRange(c.cmp, atomicUnit.Iter())
// Range deletion tombstones are often written to sstables
// untruncated on the end key side. However, they are still only
// valid within a given file's bounds. The logic for writing range
// tombstones to an output file sometimes has an incomplete view
// of range tombstones outside the file's internal key bounds. Skip
// any range tombstones completely outside file bounds.
rangeDelIter = keyspan.Truncate(
c.cmp, rangeDelIter, lowerBound.UserKey, upperBound.UserKey,
&f.Smallest, &f.Largest, false, /* panicOnUpperTruncate */
)
return rangeDelIter, closer, nil
}
func (c *compaction) String() string {
if len(c.flushing) != 0 {
return "flush\n"
}
var buf bytes.Buffer
for level := c.startLevel.level; level <= c.outputLevel.level; level++ {
i := level - c.startLevel.level
fmt.Fprintf(&buf, "%d:", level)
iter := c.inputs[i].files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
fmt.Fprintf(&buf, " %s:%s-%s", f.FileNum, f.Smallest, f.Largest)
}
fmt.Fprintf(&buf, "\n")
}
return buf.String()
}
type manualCompaction struct {
// Count of the retries either due to too many concurrent compactions, or a
// concurrent compaction to overlapping levels.
retries int
level int
outputLevel int
done chan error
start []byte
end []byte
split bool
}
type readCompaction struct {
level int
// [start, end] key ranges are used for de-duping.
start []byte
end []byte
// The file associated with the compaction.
// If the file no longer belongs in the same
// level, then we skip the compaction.
fileNum base.FileNum
}
func (d *DB) addInProgressCompaction(c *compaction) {
d.mu.compact.inProgress[c] = struct{}{}
var isBase, isIntraL0 bool
for _, cl := range c.inputs {
iter := cl.files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
if f.IsCompacting() {
d.opts.Logger.Fatalf("L%d->L%d: %s already being compacted", c.startLevel.level, c.outputLevel.level, f.FileNum)
}
f.SetCompactionState(manifest.CompactionStateCompacting)
if c.startLevel != nil && c.outputLevel != nil && c.startLevel.level == 0 {
if c.outputLevel.level == 0 {
f.IsIntraL0Compacting = true
isIntraL0 = true
} else {
isBase = true
}
}
}
}
if (isIntraL0 || isBase) && c.version.L0Sublevels != nil {
l0Inputs := []manifest.LevelSlice{c.startLevel.files}
if isIntraL0 {
l0Inputs = append(l0Inputs, c.outputLevel.files)
}
if err := c.version.L0Sublevels.UpdateStateForStartedCompaction(l0Inputs, isBase); err != nil {
d.opts.Logger.Fatalf("could not update state for compaction: %s", err)
}
}
}
// Removes compaction markers from files in a compaction. The rollback parameter
// indicates whether the compaction state should be rolled back to its original
// state in the case of an unsuccessful compaction.
//
// DB.mu must be held when calling this method, however this method can drop and
// re-acquire that mutex. All writes to the manifest for this compaction should
// have completed by this point.
func (d *DB) clearCompactingState(c *compaction, rollback bool) {
c.versionEditApplied = true
for _, cl := range c.inputs {
iter := cl.files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
if !f.IsCompacting() {
d.opts.Logger.Fatalf("L%d->L%d: %s not being compacted", c.startLevel.level, c.outputLevel.level, f.FileNum)
}
if !rollback {
// On success all compactions other than move-compactions transition the
// file into the Compacted state. Move-compacted files become eligible
// for compaction again and transition back to NotCompacting.
if c.kind != compactionKindMove {
f.SetCompactionState(manifest.CompactionStateCompacted)
} else {
f.SetCompactionState(manifest.CompactionStateNotCompacting)
}
} else {
// Else, on rollback, all input files unconditionally transition back to
// NotCompacting.
f.SetCompactionState(manifest.CompactionStateNotCompacting)
}
f.IsIntraL0Compacting = false
}
}
l0InProgress := inProgressL0Compactions(d.getInProgressCompactionInfoLocked(c))
func() {
// InitCompactingFileInfo requires that no other manifest writes be
// happening in parallel with it, i.e. we're not in the midst of installing
// another version. Otherwise, it's possible that we've created another
// L0Sublevels instance, but not added it to the versions list, causing
// all the indices in FileMetadata to be inaccurate. To ensure this,
// grab the manifest lock.
d.mu.versions.logLock()
defer d.mu.versions.logUnlock()
d.mu.versions.currentVersion().L0Sublevels.InitCompactingFileInfo(l0InProgress)
}()
}
func (d *DB) calculateDiskAvailableBytes() uint64 {
if space, err := d.opts.FS.GetDiskUsage(d.dirname); err == nil {
d.diskAvailBytes.Store(space.AvailBytes)
return space.AvailBytes
} else if !errors.Is(err, vfs.ErrUnsupported) {
d.opts.EventListener.BackgroundError(err)
}
return d.diskAvailBytes.Load()
}
func (d *DB) getDeletionPacerInfo() deletionPacerInfo {
var pacerInfo deletionPacerInfo
// Call GetDiskUsage after every file deletion. This may seem inefficient,
// but in practice this was observed to take constant time, regardless of
// volume size used, at least on linux with ext4 and zfs. All invocations
// take 10 microseconds or less.
pacerInfo.freeBytes = d.calculateDiskAvailableBytes()
d.mu.Lock()
pacerInfo.obsoleteBytes = d.mu.versions.metrics.Table.ObsoleteSize
pacerInfo.liveBytes = uint64(d.mu.versions.metrics.Total().Size)
d.mu.Unlock()
return pacerInfo
}
// onObsoleteTableDelete is called to update metrics when an sstable is deleted.
func (d *DB) onObsoleteTableDelete(fileSize uint64) {
d.mu.Lock()
d.mu.versions.metrics.Table.ObsoleteCount--
d.mu.versions.metrics.Table.ObsoleteSize -= fileSize
d.mu.Unlock()
}
// maybeScheduleFlush schedules a flush if necessary.
//
// d.mu must be held when calling this.
func (d *DB) maybeScheduleFlush() {
if d.mu.compact.flushing || d.closed.Load() != nil || d.opts.ReadOnly {
return
}
if len(d.mu.mem.queue) <= 1 {
return
}
if !d.passedFlushThreshold() {
return
}
d.mu.compact.flushing = true
go d.flush()
}
func (d *DB) passedFlushThreshold() bool {
var n int
var size uint64
for ; n < len(d.mu.mem.queue)-1; n++ {
if !d.mu.mem.queue[n].readyForFlush() {
break
}
if d.mu.mem.queue[n].flushForced {
// A flush was forced. Pretend the memtable size is the configured
// size. See minFlushSize below.
size += d.opts.MemTableSize
} else {
size += d.mu.mem.queue[n].totalBytes()
}
}
if n == 0 {
// None of the immutable memtables are ready for flushing.
return false
}
// Only flush once the sum of the queued memtable sizes exceeds half the
// configured memtable size. This prevents flushing of memtables at startup
// while we're undergoing the ramp period on the memtable size. See
// DB.newMemTable().
minFlushSize := d.opts.MemTableSize / 2
return size >= minFlushSize
}
func (d *DB) maybeScheduleDelayedFlush(tbl *memTable, dur time.Duration) {
var mem *flushableEntry
for _, m := range d.mu.mem.queue {
if m.flushable == tbl {
mem = m
break
}
}
if mem == nil || mem.flushForced {
return
}
deadline := d.timeNow().Add(dur)
if !mem.delayedFlushForcedAt.IsZero() && deadline.After(mem.delayedFlushForcedAt) {
// Already scheduled to flush sooner than within `dur`.
return
}
mem.delayedFlushForcedAt = deadline
go func() {
timer := time.NewTimer(dur)
defer timer.Stop()
select {
case <-d.closedCh:
return
case <-mem.flushed:
return
case <-timer.C:
d.commit.mu.Lock()
defer d.commit.mu.Unlock()
d.mu.Lock()
defer d.mu.Unlock()
// NB: The timer may fire concurrently with a call to Close. If a
// Close call beat us to acquiring d.mu, d.closed holds ErrClosed,
// and it's too late to flush anything. Otherwise, the Close call
// will block on locking d.mu until we've finished scheduling the
// flush and set `d.mu.compact.flushing` to true. Close will wait
// for the current flush to complete.
if d.closed.Load() != nil {
return
}
if d.mu.mem.mutable == tbl {
d.makeRoomForWrite(nil)
} else {
mem.flushForced = true
}
d.maybeScheduleFlush()
}
}()
}
func (d *DB) flush() {
pprof.Do(context.Background(), flushLabels, func(context.Context) {
flushingWorkStart := time.Now()
d.mu.Lock()
defer d.mu.Unlock()
idleDuration := flushingWorkStart.Sub(d.mu.compact.noOngoingFlushStartTime)
var bytesFlushed uint64
var err error
if bytesFlushed, err = d.flush1(); err != nil {
// TODO(peter): count consecutive flush errors and backoff.
d.opts.EventListener.BackgroundError(err)
}
d.mu.compact.flushing = false
d.mu.compact.noOngoingFlushStartTime = time.Now()
workDuration := d.mu.compact.noOngoingFlushStartTime.Sub(flushingWorkStart)
d.mu.compact.flushWriteThroughput.Bytes += int64(bytesFlushed)
d.mu.compact.flushWriteThroughput.WorkDuration += workDuration
d.mu.compact.flushWriteThroughput.IdleDuration += idleDuration
// More flush work may have arrived while we were flushing, so schedule
// another flush if needed.
d.maybeScheduleFlush()
// The flush may have produced too many files in a level, so schedule a
// compaction if needed.
d.maybeScheduleCompaction()
d.mu.compact.cond.Broadcast()
})
}
// runIngestFlush is used to generate a flush version edit for sstables which
// were ingested as flushables. Both DB.mu and the manifest lock must be held
// while runIngestFlush is called.
func (d *DB) runIngestFlush(c *compaction) (*manifest.VersionEdit, error) {
if len(c.flushing) != 1 {
panic("pebble: ingestedFlushable must be flushed one at a time.")
}
// Construct the VersionEdit, levelMetrics etc.
c.metrics = make(map[int]*LevelMetrics, numLevels)
// Finding the target level for ingestion must use the latest version
// after the logLock has been acquired.
c.version = d.mu.versions.currentVersion()
baseLevel := d.mu.versions.picker.getBaseLevel()
iterOpts := IterOptions{logger: d.opts.Logger}
ve := &versionEdit{}
var level int
var err error
var fileToSplit *fileMetadata
var ingestSplitFiles []ingestSplitFile
for _, file := range c.flushing[0].flushable.(*ingestedFlushable).files {
suggestSplit := d.opts.Experimental.IngestSplit != nil && d.opts.Experimental.IngestSplit() &&
d.FormatMajorVersion() >= FormatVirtualSSTables
level, fileToSplit, err = ingestTargetLevel(
d.newIters, d.tableNewRangeKeyIter, iterOpts, d.opts.Comparer,
c.version, baseLevel, d.mu.compact.inProgress, file.FileMetadata,
suggestSplit,
)
if err != nil {
return nil, err
}
ve.NewFiles = append(ve.NewFiles, newFileEntry{Level: level, Meta: file.FileMetadata})
if fileToSplit != nil {
ingestSplitFiles = append(ingestSplitFiles, ingestSplitFile{
ingestFile: file.FileMetadata,
splitFile: fileToSplit,
level: level,
})
}
levelMetrics := c.metrics[level]
if levelMetrics == nil {
levelMetrics = &LevelMetrics{}
c.metrics[level] = levelMetrics
}
levelMetrics.BytesIngested += file.Size
levelMetrics.TablesIngested++
}
updateLevelMetricsOnExcise := func(m *fileMetadata, level int, added []newFileEntry) {
levelMetrics := c.metrics[level]
if levelMetrics == nil {
levelMetrics = &LevelMetrics{}
c.metrics[level] = levelMetrics
}
levelMetrics.NumFiles--
levelMetrics.Size -= int64(m.Size)
for i := range added {
levelMetrics.NumFiles++
levelMetrics.Size += int64(added[i].Meta.Size)
}
}
if len(ingestSplitFiles) > 0 {
ve.DeletedFiles = make(map[manifest.DeletedFileEntry]*manifest.FileMetadata)
replacedFiles := make(map[base.FileNum][]newFileEntry)
if err := d.ingestSplit(ve, updateLevelMetricsOnExcise, ingestSplitFiles, replacedFiles); err != nil {
return nil, err
}
}
return ve, nil
}
// flush runs a compaction that copies the immutable memtables from memory to
// disk.
//
// d.mu must be held when calling this, but the mutex may be dropped and
// re-acquired during the course of this method.
func (d *DB) flush1() (bytesFlushed uint64, err error) {
// NB: The flushable queue can contain flushables of type ingestedFlushable.
// The sstables in ingestedFlushable.files must be placed into the appropriate
// level in the lsm. Let's say the flushable queue contains a prefix of
// regular immutable memtables, then an ingestedFlushable, and then the
// mutable memtable. When the flush of the ingestedFlushable is performed,
// it needs an updated view of the lsm. That is, the prefix of immutable
// memtables must have already been flushed. Similarly, if there are two
// contiguous ingestedFlushables in the queue, then the first flushable must
// be flushed, so that the second flushable can see an updated view of the
// lsm.
//
// Given the above, we restrict flushes to either some prefix of regular
// memtables, or a single flushable of type ingestedFlushable. The DB.flush
// function will call DB.maybeScheduleFlush again, so a new flush to finish
// the remaining flush work should be scheduled right away.
//
// NB: Large batches placed in the flushable queue share the WAL with the
// previous memtable in the queue. We must ensure the property that both the
// large batch and the memtable with which it shares a WAL are flushed
// together. The property ensures that the minimum unflushed log number
// isn't incremented incorrectly. Since a flushableBatch.readyToFlush always
// returns true, and since the large batch will always be placed right after
// the memtable with which it shares a WAL, the property is naturally
// ensured. The large batch will always be placed after the memtable with
// which it shares a WAL because we ensure it in DB.commitWrite by holding
// the commitPipeline.mu and then holding DB.mu. As an extra defensive
// measure, if we try to flush the memtable without also flushing the
// flushable batch in the same flush, since the memtable and flushableBatch
// have the same logNum, the logNum invariant check below will trigger.
var n, inputs int
var inputBytes uint64
var ingest bool
for ; n < len(d.mu.mem.queue)-1; n++ {
if f, ok := d.mu.mem.queue[n].flushable.(*ingestedFlushable); ok {
if n == 0 {
// The first flushable is of type ingestedFlushable. Since these
// must be flushed individually, we perform a flush for just
// this.
if !f.readyForFlush() {
// This check is almost unnecessary, but we guard against it
// just in case this invariant changes in the future.
panic("pebble: ingestedFlushable should always be ready to flush.")
}
// By setting n = 1, we ensure that the first flushable(n == 0)
// is scheduled for a flush. The number of tables added is equal to the
// number of files in the ingest operation.
n = 1
inputs = len(f.files)
ingest = true
break
} else {
// There was some prefix of flushables which weren't of type
// ingestedFlushable. So, perform a flush for those.
break
}
}
if !d.mu.mem.queue[n].readyForFlush() {
break
}
inputBytes += d.mu.mem.queue[n].inuseBytes()
}
if n == 0 {
// None of the immutable memtables are ready for flushing.
return 0, nil
}
if !ingest {
// Flushes of memtables add the prefix of n memtables from the flushable
// queue.
inputs = n
}
// Require that every memtable being flushed has a log number less than the
// new minimum unflushed log number.
minUnflushedLogNum := d.mu.mem.queue[n].logNum
if !d.opts.DisableWAL {
for i := 0; i < n; i++ {
if logNum := d.mu.mem.queue[i].logNum; logNum >= minUnflushedLogNum {
panic(errors.AssertionFailedf("logNum invariant violated: flushing %d items; %d:type=%T,logNum=%d; %d:type=%T,logNum=%d",
n,
i, d.mu.mem.queue[i].flushable, logNum,
n, d.mu.mem.queue[n].flushable, minUnflushedLogNum))
}
}
}
c := newFlush(d.opts, d.mu.versions.currentVersion(),
d.mu.versions.picker.getBaseLevel(), d.mu.mem.queue[:n], d.timeNow())
d.addInProgressCompaction(c)
jobID := d.mu.nextJobID
d.mu.nextJobID++
d.opts.EventListener.FlushBegin(FlushInfo{
JobID: jobID,
Input: inputs,
InputBytes: inputBytes,
Ingest: ingest,
})
startTime := d.timeNow()
var ve *manifest.VersionEdit
var pendingOutputs []physicalMeta
var stats compactStats
// To determine the target level of the files in the ingestedFlushable, we
// need to acquire the logLock, and not release it for that duration. Since,
// we need to acquire the logLock below to perform the logAndApply step
// anyway, we create the VersionEdit for ingestedFlushable outside of
// runCompaction. For all other flush cases, we construct the VersionEdit
// inside runCompaction.
if c.kind != compactionKindIngestedFlushable {
ve, pendingOutputs, stats, err = d.runCompaction(jobID, c)
}
// Acquire logLock. This will be released either on an error, by way of
// logUnlock, or through a call to logAndApply if there is no error.
d.mu.versions.logLock()
if c.kind == compactionKindIngestedFlushable {
ve, err = d.runIngestFlush(c)
}
info := FlushInfo{
JobID: jobID,
Input: inputs,
InputBytes: inputBytes,
Duration: d.timeNow().Sub(startTime),
Done: true,
Ingest: ingest,
Err: err,
}
if err == nil {
for i := range ve.NewFiles {
e := &ve.NewFiles[i]
info.Output = append(info.Output, e.Meta.TableInfo())
// Ingested tables are not necessarily flushed to L0. Record the level of
// each ingested file explicitly.
if ingest {
info.IngestLevels = append(info.IngestLevels, e.Level)
}
}
if len(ve.NewFiles) == 0 {
info.Err = errEmptyTable
}
// The flush succeeded or it produced an empty sstable. In either case we
// want to bump the minimum unflushed log number to the log number of the
// oldest unflushed memtable.
ve.MinUnflushedLogNum = minUnflushedLogNum
if c.kind != compactionKindIngestedFlushable {
metrics := c.metrics[0]
if d.opts.DisableWAL {
// If the WAL is disabled, every flushable has a zero [logSize],
// resulting in zero bytes in. Instead, use the number of bytes we
// flushed as the BytesIn. This ensures we get a reasonable w-amp
// calculation even when the WAL is disabled.
metrics.BytesIn = metrics.BytesFlushed
} else {
metrics := c.metrics[0]
for i := 0; i < n; i++ {
metrics.BytesIn += d.mu.mem.queue[i].logSize
}
}
} else if len(ve.DeletedFiles) > 0 {
// c.kind == compactionKindIngestedFlushable && we have deleted files due
// to ingest-time splits.
//
// Iterate through all other compactions, and check if their inputs have
// been replaced due to an ingest-time split. In that case, cancel the
// compaction.
for c2 := range d.mu.compact.inProgress {
for i := range c2.inputs {
iter := c2.inputs[i].files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
if _, ok := ve.DeletedFiles[deletedFileEntry{FileNum: f.FileNum, Level: c2.inputs[i].level}]; ok {
c2.cancel.Store(true)
break
}
}
}
}
}
err = d.mu.versions.logAndApply(jobID, ve, c.metrics, false, /* forceRotation */
func() []compactionInfo { return d.getInProgressCompactionInfoLocked(c) })
if err != nil {
info.Err = err
// TODO(peter): untested.
for _, f := range pendingOutputs {
// Note that the FileBacking for the file metadata might not have
// been set yet. So, we directly use the FileNum. Since these
// files were generated as compaction outputs, these must be
// physical files on disk. This property might not hold once
// https://github.com/cockroachdb/pebble/issues/389 is
// implemented if #389 creates virtual sstables as output files.
d.mu.versions.obsoleteTables = append(
d.mu.versions.obsoleteTables,
fileInfo{f.FileNum.DiskFileNum(), f.Size},
)
}
d.mu.versions.updateObsoleteTableMetricsLocked()
}
} else {
// We won't be performing the logAndApply step because of the error,
// so logUnlock.
d.mu.versions.logUnlock()
}
bytesFlushed = c.bytesIterated
// If err != nil, then the flush will be retried, and we will recalculate
// these metrics.
if err == nil {
d.mu.snapshots.cumulativePinnedCount += stats.cumulativePinnedKeys
d.mu.snapshots.cumulativePinnedSize += stats.cumulativePinnedSize
d.mu.versions.metrics.Keys.MissizedTombstonesCount += stats.countMissizedDels
d.maybeUpdateDeleteCompactionHints(c)
}
d.clearCompactingState(c, err != nil)
delete(d.mu.compact.inProgress, c)
d.mu.versions.incrementCompactions(c.kind, c.extraLevels, c.pickerMetrics)
var flushed flushableList
if err == nil {
flushed = d.mu.mem.queue[:n]
d.mu.mem.queue = d.mu.mem.queue[n:]
d.updateReadStateLocked(d.opts.DebugCheck)
d.updateTableStatsLocked(ve.NewFiles)
if ingest {
d.mu.versions.metrics.Flush.AsIngestCount++
for _, l := range c.metrics {
d.mu.versions.metrics.Flush.AsIngestBytes += l.BytesIngested
d.mu.versions.metrics.Flush.AsIngestTableCount += l.TablesIngested
}
}
// Update if any eventually file-only snapshots have now transitioned to
// being file-only.
earliestUnflushedSeqNum := d.getEarliestUnflushedSeqNumLocked()
currentVersion := d.mu.versions.currentVersion()
for s := d.mu.snapshots.root.next; s != &d.mu.snapshots.root; {
if s.efos == nil {
s = s.next
continue
}
if base.Visible(earliestUnflushedSeqNum, s.efos.seqNum, InternalKeySeqNumMax) {
s = s.next
continue
}
if s.efos.excised.Load() {
// If a concurrent excise has happened that overlaps with one of the key
// ranges this snapshot is interested in, this EFOS cannot transition to
// a file-only snapshot as keys in that range could now be deleted. Move
// onto the next snapshot.
s = s.next
continue
}
currentVersion.Ref()
// NB: s.efos.transitionToFileOnlySnapshot could close s, in which
// case s.next would be nil. Save it before calling it.
next := s.next
_ = s.efos.transitionToFileOnlySnapshot(currentVersion)
s = next
}
}
// Signal FlushEnd after installing the new readState. This helps for unit
// tests that use the callback to trigger a read using an iterator with
// IterOptions.OnlyReadGuaranteedDurable.
info.TotalDuration = d.timeNow().Sub(startTime)
d.opts.EventListener.FlushEnd(info)
// The order of these operations matters here for ease of testing.
// Removing the reader reference first allows tests to be guaranteed that
// the memtable reservation has been released by the time a synchronous
// flush returns. readerUnrefLocked may also produce obsolete files so the
// call to deleteObsoleteFiles must happen after it.
for i := range flushed {
flushed[i].readerUnrefLocked(true)
}
d.deleteObsoleteFiles(jobID)
// Mark all the memtables we flushed as flushed.
for i := range flushed {
close(flushed[i].flushed)
}
return bytesFlushed, err
}
// maybeScheduleCompactionAsync should be used when
// we want to possibly schedule a compaction, but don't
// want to eat the cost of running maybeScheduleCompaction.
// This method should be launched in a separate goroutine.
// d.mu must not be held when this is called.
func (d *DB) maybeScheduleCompactionAsync() {
defer d.compactionSchedulers.Done()
d.mu.Lock()
d.maybeScheduleCompaction()
d.mu.Unlock()
}
// maybeScheduleCompaction schedules a compaction if necessary.
//
// d.mu must be held when calling this.
func (d *DB) maybeScheduleCompaction() {
d.maybeScheduleCompactionPicker(pickAuto)
}
func pickAuto(picker compactionPicker, env compactionEnv) *pickedCompaction {
return picker.pickAuto(env)
}
func pickElisionOnly(picker compactionPicker, env compactionEnv) *pickedCompaction {
return picker.pickElisionOnlyCompaction(env)
}
// maybeScheduleCompactionPicker schedules a compaction if necessary,
// calling `pickFunc` to pick automatic compactions.
//
// d.mu must be held when calling this.
func (d *DB) maybeScheduleCompactionPicker(
pickFunc func(compactionPicker, compactionEnv) *pickedCompaction,
) {
if d.closed.Load() != nil || d.opts.ReadOnly {
return
}
maxConcurrentCompactions := d.opts.MaxConcurrentCompactions()
if d.mu.compact.compactingCount >= maxConcurrentCompactions {
if len(d.mu.compact.manual) > 0 {
// Inability to run head blocks later manual compactions.
d.mu.compact.manual[0].retries++
}
return
}
// Compaction picking needs a coherent view of a Version. In particular, we
// need to exlude concurrent ingestions from making a decision on which level
// to ingest into that conflicts with our compaction
// decision. versionSet.logLock provides the necessary mutual exclusion.
d.mu.versions.logLock()
defer d.mu.versions.logUnlock()
// Check for the closed flag again, in case the DB was closed while we were
// waiting for logLock().
if d.closed.Load() != nil {
return
}
env := compactionEnv{
diskAvailBytes: d.diskAvailBytes.Load(),
earliestSnapshotSeqNum: d.mu.snapshots.earliest(),
earliestUnflushedSeqNum: d.getEarliestUnflushedSeqNumLocked(),
}
// Check for delete-only compactions first, because they're expected to be
// cheap and reduce future compaction work.
if !d.opts.private.disableDeleteOnlyCompactions &&
len(d.mu.compact.deletionHints) > 0 &&
!d.opts.DisableAutomaticCompactions {
v := d.mu.versions.currentVersion()
snapshots := d.mu.snapshots.toSlice()
inputs, unresolvedHints := checkDeleteCompactionHints(d.cmp, v, d.mu.compact.deletionHints, snapshots)
d.mu.compact.deletionHints = unresolvedHints
if len(inputs) > 0 {
c := newDeleteOnlyCompaction(d.opts, v, inputs, d.timeNow())
d.mu.compact.compactingCount++
d.addInProgressCompaction(c)
go d.compact(c, nil)
}
}
for len(d.mu.compact.manual) > 0 && d.mu.compact.compactingCount < maxConcurrentCompactions {
v := d.mu.versions.currentVersion()
manual := d.mu.compact.manual[0]
env.inProgressCompactions = d.getInProgressCompactionInfoLocked(nil)
pc, retryLater := pickManualCompaction(v, d.opts, env, d.mu.versions.picker.getBaseLevel(), manual)
if pc != nil {
c := newCompaction(pc, d.opts, d.timeNow(), d.ObjProvider())
d.mu.compact.manual = d.mu.compact.manual[1:]
d.mu.compact.compactingCount++
d.addInProgressCompaction(c)
go d.compact(c, manual.done)
} else if !retryLater {
// Noop
d.mu.compact.manual = d.mu.compact.manual[1:]
manual.done <- nil
} else {
// Inability to run head blocks later manual compactions.
manual.retries++
break
}
}
for !d.opts.DisableAutomaticCompactions && d.mu.compact.compactingCount < maxConcurrentCompactions {
env.inProgressCompactions = d.getInProgressCompactionInfoLocked(nil)
env.readCompactionEnv = readCompactionEnv{
readCompactions: &d.mu.compact.readCompactions,
flushing: d.mu.compact.flushing || d.passedFlushThreshold(),
rescheduleReadCompaction: &d.mu.compact.rescheduleReadCompaction,
}
pc := pickFunc(d.mu.versions.picker, env)
if pc == nil {
break
}
c := newCompaction(pc, d.opts, d.timeNow(), d.ObjProvider())
d.mu.compact.compactingCount++
d.addInProgressCompaction(c)
go d.compact(c, nil)
}
}
// deleteCompactionHintType indicates whether the deleteCompactionHint was
// generated from a span containing a range del (point key only), a range key
// delete (range key only), or both a point and range key.
type deleteCompactionHintType uint8
const (
// NOTE: While these are primarily used as enumeration types, they are also
// used for some bitwise operations. Care should be taken when updating.
deleteCompactionHintTypeUnknown deleteCompactionHintType = iota
deleteCompactionHintTypePointKeyOnly
deleteCompactionHintTypeRangeKeyOnly
deleteCompactionHintTypePointAndRangeKey
)
// String implements fmt.Stringer.
func (h deleteCompactionHintType) String() string {
switch h {
case deleteCompactionHintTypeUnknown:
return "unknown"
case deleteCompactionHintTypePointKeyOnly:
return "point-key-only"
case deleteCompactionHintTypeRangeKeyOnly:
return "range-key-only"
case deleteCompactionHintTypePointAndRangeKey:
return "point-and-range-key"
default:
panic(fmt.Sprintf("unknown hint type: %d", h))
}
}
// compactionHintFromKeys returns a deleteCompactionHintType given a slice of
// keyspan.Keys.
func compactionHintFromKeys(keys []keyspan.Key) deleteCompactionHintType {
var hintType deleteCompactionHintType
for _, k := range keys {
switch k.Kind() {
case base.InternalKeyKindRangeDelete:
hintType |= deleteCompactionHintTypePointKeyOnly
case base.InternalKeyKindRangeKeyDelete:
hintType |= deleteCompactionHintTypeRangeKeyOnly
default:
panic(fmt.Sprintf("unsupported key kind: %s", k.Kind()))
}
}
return hintType
}
// A deleteCompactionHint records a user key and sequence number span that has been
// deleted by a range tombstone. A hint is recorded if at least one sstable
// falls completely within both the user key and sequence number spans.
// Once the tombstones and the observed completely-contained sstables fall
// into the same snapshot stripe, a delete-only compaction may delete any
// sstables within the range.
type deleteCompactionHint struct {
// The type of key span that generated this hint (point key, range key, or
// both).
hintType deleteCompactionHintType
// start and end are user keys specifying a key range [start, end) of
// deleted keys.
start []byte
end []byte
// The level of the file containing the range tombstone(s) when the hint
// was created. Only lower levels need to be searched for files that may
// be deleted.
tombstoneLevel int
// The file containing the range tombstone(s) that created the hint.
tombstoneFile *fileMetadata
// The smallest and largest sequence numbers of the abutting tombstones
// merged to form this hint. All of a tables' keys must be less than the
// tombstone smallest sequence number to be deleted. All of a tables'
// sequence numbers must fall into the same snapshot stripe as the
// tombstone largest sequence number to be deleted.
tombstoneLargestSeqNum uint64
tombstoneSmallestSeqNum uint64
// The smallest sequence number of a sstable that was found to be covered
// by this hint. The hint cannot be resolved until this sequence number is
// in the same snapshot stripe as the largest tombstone sequence number.
// This is set when a hint is created, so the LSM may look different and
// notably no longer contain the sstable that contained the key at this
// sequence number.
fileSmallestSeqNum uint64
}
func (h deleteCompactionHint) String() string {
return fmt.Sprintf(
"L%d.%s %s-%s seqnums(tombstone=%d-%d, file-smallest=%d, type=%s)",
h.tombstoneLevel, h.tombstoneFile.FileNum, h.start, h.end,
h.tombstoneSmallestSeqNum, h.tombstoneLargestSeqNum, h.fileSmallestSeqNum,
h.hintType,
)
}
func (h *deleteCompactionHint) canDelete(cmp Compare, m *fileMetadata, snapshots []uint64) bool {
// The file can only be deleted if all of its keys are older than the
// earliest tombstone aggregated into the hint.
if m.LargestSeqNum >= h.tombstoneSmallestSeqNum || m.SmallestSeqNum < h.fileSmallestSeqNum {
return false
}
// The file's oldest key must be in the same snapshot stripe as the
// newest tombstone. NB: We already checked the hint's sequence numbers,
// but this file's oldest sequence number might be lower than the hint's
// smallest sequence number despite the file falling within the key range
// if this file was constructed after the hint by a compaction.
ti, _ := snapshotIndex(h.tombstoneLargestSeqNum, snapshots)
fi, _ := snapshotIndex(m.SmallestSeqNum, snapshots)
if ti != fi {
return false
}
switch h.hintType {
case deleteCompactionHintTypePointKeyOnly:
// A hint generated by a range del span cannot delete tables that contain
// range keys.
if m.HasRangeKeys {
return false
}
case deleteCompactionHintTypeRangeKeyOnly:
// A hint generated by a range key del span cannot delete tables that
// contain point keys.
if m.HasPointKeys {
return false
}
case deleteCompactionHintTypePointAndRangeKey:
// A hint from a span that contains both range dels *and* range keys can
// only be deleted if both bounds fall within the hint. The next check takes
// care of this.
default:
panic(fmt.Sprintf("pebble: unknown delete compaction hint type: %d", h.hintType))
}
// The file's keys must be completely contained within the hint range.
return cmp(h.start, m.Smallest.UserKey) <= 0 && cmp(m.Largest.UserKey, h.end) < 0
}
func (d *DB) maybeUpdateDeleteCompactionHints(c *compaction) {
// Compactions that zero sequence numbers can interfere with compaction
// deletion hints. Deletion hints apply to tables containing keys older
// than a threshold. If a key more recent than the threshold is zeroed in
// a compaction, a delete-only compaction may mistake it as meeting the
// threshold and drop a table containing live data.
//
// To avoid this scenario, compactions that zero sequence numbers remove
// any conflicting deletion hints. A deletion hint is conflicting if both
// of the following conditions apply:
// * its key space overlaps with the compaction
// * at least one of its inputs contains a key as recent as one of the
// hint's tombstones.
//
if !c.allowedZeroSeqNum {
return
}
updatedHints := d.mu.compact.deletionHints[:0]
for _, h := range d.mu.compact.deletionHints {
// If the compaction's key space is disjoint from the hint's key
// space, the zeroing of sequence numbers won't affect the hint. Keep
// the hint.
keysDisjoint := d.cmp(h.end, c.smallest.UserKey) < 0 || d.cmp(h.start, c.largest.UserKey) > 0
if keysDisjoint {
updatedHints = append(updatedHints, h)
continue
}
// All of the compaction's inputs must be older than the hint's
// tombstones.
inputsOlder := true
for _, in := range c.inputs {
iter := in.files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
inputsOlder = inputsOlder && f.LargestSeqNum < h.tombstoneSmallestSeqNum
}
}
if inputsOlder {
updatedHints = append(updatedHints, h)
continue
}
// Drop h, because the compaction c may have zeroed sequence numbers
// of keys more recent than some of h's tombstones.
}
d.mu.compact.deletionHints = updatedHints
}
func checkDeleteCompactionHints(
cmp Compare, v *version, hints []deleteCompactionHint, snapshots []uint64,
) ([]compactionLevel, []deleteCompactionHint) {
var files map[*fileMetadata]bool
var byLevel [numLevels][]*fileMetadata
unresolvedHints := hints[:0]
for _, h := range hints {
// Check each compaction hint to see if it's resolvable. Resolvable
// hints are removed and trigger a delete-only compaction if any files
// in the current LSM still meet their criteria. Unresolvable hints
// are saved and don't trigger a delete-only compaction.
//
// When a compaction hint is created, the sequence numbers of the
// range tombstones and the covered file with the oldest key are
// recorded. The largest tombstone sequence number and the smallest
// file sequence number must be in the same snapshot stripe for the
// hint to be resolved. The below graphic models a compaction hint
// covering the keyspace [b, r). The hint completely contains two
// files, 000002 and 000003. The file 000003 contains the lowest
// covered sequence number at #90. The tombstone b.RANGEDEL.230:h has
// the highest tombstone sequence number incorporated into the hint.
// The hint may be resolved only once the snapshots at #100, #180 and
// #210 are all closed. File 000001 is not included within the hint
// because it extends beyond the range tombstones in user key space.
//
// 250
//
// |-b...230:h-|
// _____________________________________________________ snapshot #210
// 200 |--h.RANGEDEL.200:r--|
//
// _____________________________________________________ snapshot #180
//
// 150 +--------+
// +---------+ | 000003 |
// | 000002 | | |
// +_________+ | |
// 100_____________________|________|___________________ snapshot #100
// +--------+
// _____________________________________________________ snapshot #70
// +---------------+
// 50 | 000001 |
// | |
// +---------------+
// ______________________________________________________________
// a b c d e f g h i j k l m n o p q r s t u v w x y z
ti, _ := snapshotIndex(h.tombstoneLargestSeqNum, snapshots)
fi, _ := snapshotIndex(h.fileSmallestSeqNum, snapshots)
if ti != fi {
// Cannot resolve yet.
unresolvedHints = append(unresolvedHints, h)
continue
}
// The hint h will be resolved and dropped, regardless of whether
// there are any tables that can be deleted.
for l := h.tombstoneLevel + 1; l < numLevels; l++ {
overlaps := v.Overlaps(l, cmp, h.start, h.end, true /* exclusiveEnd */)
iter := overlaps.Iter()
for m := iter.First(); m != nil; m = iter.Next() {
if m.IsCompacting() || !h.canDelete(cmp, m, snapshots) || files[m] {
continue
}
if files == nil {
// Construct files lazily, assuming most calls will not
// produce delete-only compactions.
files = make(map[*fileMetadata]bool)
}
files[m] = true
byLevel[l] = append(byLevel[l], m)
}
}
}
var compactLevels []compactionLevel
for l, files := range byLevel {
if len(files) == 0 {
continue
}
compactLevels = append(compactLevels, compactionLevel{
level: l,
files: manifest.NewLevelSliceKeySorted(cmp, files),
})
}
return compactLevels, unresolvedHints
}
// compact runs one compaction and maybe schedules another call to compact.
func (d *DB) compact(c *compaction, errChannel chan error) {
pprof.Do(context.Background(), compactLabels, func(context.Context) {
d.mu.Lock()
defer d.mu.Unlock()
if err := d.compact1(c, errChannel); err != nil {
// TODO(peter): count consecutive compaction errors and backoff.
d.opts.EventListener.BackgroundError(err)
}
d.mu.compact.compactingCount--
delete(d.mu.compact.inProgress, c)
// Add this compaction's duration to the cumulative duration. NB: This
// must be atomic with the above removal of c from
// d.mu.compact.InProgress to ensure Metrics.Compact.Duration does not
// miss or double count a completing compaction's duration.
d.mu.compact.duration += d.timeNow().Sub(c.beganAt)
// The previous compaction may have produced too many files in a
// level, so reschedule another compaction if needed.
d.maybeScheduleCompaction()
d.mu.compact.cond.Broadcast()
})
}
// compact1 runs one compaction.
//
// d.mu must be held when calling this, but the mutex may be dropped and
// re-acquired during the course of this method.
func (d *DB) compact1(c *compaction, errChannel chan error) (err error) {
if errChannel != nil {
defer func() {
errChannel <- err
}()
}
jobID := d.mu.nextJobID
d.mu.nextJobID++
info := c.makeInfo(jobID)
d.opts.EventListener.CompactionBegin(info)
startTime := d.timeNow()
ve, pendingOutputs, stats, err := d.runCompaction(jobID, c)
info.Duration = d.timeNow().Sub(startTime)
if err == nil {
err = func() error {
var err error
d.mu.versions.logLock()
// Check if this compaction had a conflicting operation (eg. a d.excise())
// that necessitates it restarting from scratch. Note that since we hold
// the manifest lock, we don't expect this bool to change its value
// as only the holder of the manifest lock will ever write to it.
if c.cancel.Load() {
err = firstError(err, ErrCancelledCompaction)
}
if err != nil {
// logAndApply calls logUnlock. If we didn't call it, we need to call
// logUnlock ourselves.
d.mu.versions.logUnlock()
return err
}
return d.mu.versions.logAndApply(jobID, ve, c.metrics, false /* forceRotation */, func() []compactionInfo {
return d.getInProgressCompactionInfoLocked(c)
})
}()
if err != nil {
// TODO(peter): untested.
for _, f := range pendingOutputs {
// Note that the FileBacking for the file metadata might not have
// been set yet. So, we directly use the FileNum. Since these
// files were generated as compaction outputs, these must be
// physical files on disk. This property might not hold once
// https://github.com/cockroachdb/pebble/issues/389 is
// implemented if #389 creates virtual sstables as output files.
d.mu.versions.obsoleteTables = append(
d.mu.versions.obsoleteTables,
fileInfo{f.FileNum.DiskFileNum(), f.Size},
)
}
d.mu.versions.updateObsoleteTableMetricsLocked()
}
}
info.Done = true
info.Err = err
if err == nil {
for i := range ve.NewFiles {
e := &ve.NewFiles[i]
info.Output.Tables = append(info.Output.Tables, e.Meta.TableInfo())
}
d.mu.snapshots.cumulativePinnedCount += stats.cumulativePinnedKeys
d.mu.snapshots.cumulativePinnedSize += stats.cumulativePinnedSize
d.mu.versions.metrics.Keys.MissizedTombstonesCount += stats.countMissizedDels
d.maybeUpdateDeleteCompactionHints(c)
}
// NB: clearing compacting state must occur before updating the read state;
// L0Sublevels initialization depends on it.
d.clearCompactingState(c, err != nil)
d.mu.versions.incrementCompactions(c.kind, c.extraLevels, c.pickerMetrics)
d.mu.versions.incrementCompactionBytes(-c.bytesWritten)
info.TotalDuration = d.timeNow().Sub(c.beganAt)
d.opts.EventListener.CompactionEnd(info)
// Update the read state before deleting obsolete files because the
// read-state update will cause the previous version to be unref'd and if
// there are no references obsolete tables will be added to the obsolete
// table list.
if err == nil {
d.updateReadStateLocked(d.opts.DebugCheck)
d.updateTableStatsLocked(ve.NewFiles)
}
d.deleteObsoleteFiles(jobID)
return err
}
type compactStats struct {
cumulativePinnedKeys uint64
cumulativePinnedSize uint64
countMissizedDels uint64
}
// runCopyCompaction runs a copy compaction where a new FileNum is created that
// is a byte-for-byte copy of the input file. This is used in lieu of a move
// compaction when a file is being moved across the local/remote storage
// boundary.
//
// d.mu must be held when calling this method.
func (d *DB) runCopyCompaction(
jobID int,
c *compaction,
meta *fileMetadata,
objMeta objstorage.ObjectMetadata,
versionEdit *versionEdit,
) (ve *versionEdit, pendingOutputs []physicalMeta, retErr error) {
ve = versionEdit
if objMeta.IsRemote() || !remote.ShouldCreateShared(d.opts.Experimental.CreateOnShared, c.outputLevel.level) {
panic("pebble: scheduled a copy compaction that is not actually moving files to shared storage")
}
// Note that based on logic in the compaction picker, we're guaranteed
// meta.Virtual is false.
if meta.Virtual {
panic(errors.AssertionFailedf("cannot do a copy compaction of a virtual sstable across local/remote storage"))
}
// We are in the relatively more complex case where we need to copy this
// file to remote/shared storage. Drop the db mutex while we do the
// copy.
//
// To ease up cleanup of the local file and tracking of refs, we create
// a new FileNum. This has the potential of making the block cache less
// effective, however.
metaCopy := new(fileMetadata)
*metaCopy = fileMetadata{
Size: meta.Size,
CreationTime: meta.CreationTime,
SmallestSeqNum: meta.SmallestSeqNum,
LargestSeqNum: meta.LargestSeqNum,
Stats: meta.Stats,
Virtual: meta.Virtual,
}
if meta.HasPointKeys {
metaCopy.ExtendPointKeyBounds(c.cmp, meta.SmallestPointKey, meta.LargestPointKey)
}
if meta.HasRangeKeys {
metaCopy.ExtendRangeKeyBounds(c.cmp, meta.SmallestRangeKey, meta.LargestRangeKey)
}
metaCopy.FileNum = d.mu.versions.getNextFileNum()
metaCopy.InitPhysicalBacking()
c.metrics = map[int]*LevelMetrics{
c.outputLevel.level: {
BytesIn: meta.Size,
BytesCompacted: meta.Size,
TablesCompacted: 1,
},
}
pendingOutputs = append(pendingOutputs, metaCopy.PhysicalMeta())
// Before dropping the db mutex, grab a ref to the current version. This
// prevents any concurrent excises from deleting files that this compaction
// needs to read/maintain a reference to.
vers := d.mu.versions.currentVersion()
vers.Ref()
defer vers.UnrefLocked()
d.mu.Unlock()
defer d.mu.Lock()
_, err := d.objProvider.LinkOrCopyFromLocal(context.TODO(), d.opts.FS,
d.objProvider.Path(objMeta), fileTypeTable, metaCopy.FileBacking.DiskFileNum,
objstorage.CreateOptions{PreferSharedStorage: true})
if err != nil {
return ve, pendingOutputs, err
}
ve.NewFiles[0].Meta = metaCopy
if err := d.objProvider.Sync(); err != nil {
return nil, pendingOutputs, err
}
return ve, pendingOutputs, nil
}
// runCompactions runs a compaction that produces new on-disk tables from
// memtables or old on-disk tables.
//
// d.mu must be held when calling this, but the mutex may be dropped and
// re-acquired during the course of this method.
func (d *DB) runCompaction(
jobID int, c *compaction,
) (ve *versionEdit, pendingOutputs []physicalMeta, stats compactStats, retErr error) {
// As a sanity check, confirm that the smallest / largest keys for new and
// deleted files in the new versionEdit pass a validation function before
// returning the edit.
defer func() {
// If we're handling a panic, don't expect the version edit to validate.
if r := recover(); r != nil {
panic(r)
} else if ve != nil {
err := validateVersionEdit(ve, d.opts.Experimental.KeyValidationFunc, d.opts.Comparer.FormatKey)
if err != nil {
d.opts.Logger.Fatalf("pebble: version edit validation failed: %s", err)
}
}
}()
// Check for a delete-only compaction. This can occur when wide range
// tombstones completely contain sstables.
if c.kind == compactionKindDeleteOnly {
c.metrics = make(map[int]*LevelMetrics, len(c.inputs))
ve := &versionEdit{
DeletedFiles: map[deletedFileEntry]*fileMetadata{},
}
for _, cl := range c.inputs {
levelMetrics := &LevelMetrics{}
iter := cl.files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
ve.DeletedFiles[deletedFileEntry{
Level: cl.level,
FileNum: f.FileNum,
}] = f
}
c.metrics[cl.level] = levelMetrics
}
return ve, nil, stats, nil
}
if c.kind == compactionKindIngestedFlushable {
panic("pebble: runCompaction cannot handle compactionKindIngestedFlushable.")
}
// Check for a move or copy of one table from one level to the next. We avoid
// such a move if there is lots of overlapping grandparent data. Otherwise,
// the move could create a parent file that will require a very expensive
// merge later on.
if c.kind == compactionKindMove || c.kind == compactionKindCopy {
iter := c.startLevel.files.Iter()
meta := iter.First()
if invariants.Enabled {
if iter.Next() != nil {
panic("got more than one file for a move or copy compaction")
}
}
if c.cancel.Load() {
return ve, nil, stats, ErrCancelledCompaction
}
objMeta, err := d.objProvider.Lookup(fileTypeTable, meta.FileBacking.DiskFileNum)
if err != nil {
return ve, pendingOutputs, stats, err
}
c.metrics = map[int]*LevelMetrics{
c.outputLevel.level: {
BytesMoved: meta.Size,
TablesMoved: 1,
},
}
ve := &versionEdit{
DeletedFiles: map[deletedFileEntry]*fileMetadata{
{Level: c.startLevel.level, FileNum: meta.FileNum}: meta,
},
NewFiles: []newFileEntry{
{Level: c.outputLevel.level, Meta: meta},
},
}
if c.kind == compactionKindCopy {
ve, pendingOutputs, retErr = d.runCopyCompaction(jobID, c, meta, objMeta, ve)
if retErr != nil {
return ve, pendingOutputs, stats, retErr
}
}
return ve, nil, stats, nil
}
defer func() {
if retErr != nil {
pendingOutputs = nil
}
}()
snapshots := d.mu.snapshots.toSlice()
formatVers := d.FormatMajorVersion()
if c.flushing == nil {
// Before dropping the db mutex, grab a ref to the current version. This
// prevents any concurrent excises from deleting files that this compaction
// needs to read/maintain a reference to.
//
// Note that unlike user iterators, compactionIter does not maintain a ref
// of the version or read state.
vers := d.mu.versions.currentVersion()
vers.Ref()
defer vers.UnrefLocked()
}
if c.cancel.Load() {
return ve, nil, stats, ErrCancelledCompaction
}
// Release the d.mu lock while doing I/O.
// Note the unusual order: Unlock and then Lock.
d.mu.Unlock()
defer d.mu.Lock()
// Compactions use a pool of buffers to read blocks, avoiding polluting the
// block cache with blocks that will not be read again. We initialize the
// buffer pool with a size 12. This initial size does not need to be
// accurate, because the pool will grow to accommodate the maximum number of
// blocks allocated at a given time over the course of the compaction. But
// choosing a size larger than that working set avoids any additional
// allocations to grow the size of the pool over the course of iteration.
//
// Justification for initial size 12: In a two-level compaction, at any
// given moment we'll have 2 index blocks in-use and 2 data blocks in-use.
// Additionally, when decoding a compressed block, we'll temporarily
// allocate 1 additional block to hold the compressed buffer. In the worst
// case that all input sstables have two-level index blocks (+2), value
// blocks (+2), range deletion blocks (+n) and range key blocks (+n), we'll
// additionally require 2n+4 blocks where n is the number of input sstables.
// Range deletion and range key blocks are relatively rare, and the cost of
// an additional allocation or two over the course of the compaction is
// considered to be okay. A larger initial size would cause the pool to hold
// on to more memory, even when it's not in-use because the pool will
// recycle buffers up to the current capacity of the pool. The memory use of
// a 12-buffer pool is expected to be within reason, even if all the buffers
// grow to the typical size of an index block (256 KiB) which would
// translate to 3 MiB per compaction.
c.bufferPool.Init(12)
defer c.bufferPool.Release()
iiter, err := c.newInputIter(d.newIters, d.tableNewRangeKeyIter, snapshots)
if err != nil {
return nil, pendingOutputs, stats, err
}
c.allowedZeroSeqNum = c.allowZeroSeqNum()
iiter = invalidating.MaybeWrapIfInvariants(iiter)
iter := newCompactionIter(c.cmp, c.equal, c.formatKey, d.merge, iiter, snapshots,
&c.rangeDelFrag, &c.rangeKeyFrag, c.allowedZeroSeqNum, c.elideTombstone,
c.elideRangeTombstone, d.FormatMajorVersion())
var (
createdFiles []base.DiskFileNum
tw *sstable.Writer
pinnedKeySize uint64
pinnedValueSize uint64
pinnedCount uint64
)
defer func() {
if iter != nil {
retErr = firstError(retErr, iter.Close())
}
if tw != nil {
retErr = firstError(retErr, tw.Close())
}
if retErr != nil {
for _, fileNum := range createdFiles {
_ = d.objProvider.Remove(fileTypeTable, fileNum)
}
}
for _, closer := range c.closers {
retErr = firstError(retErr, closer.Close())
}
}()
ve = &versionEdit{
DeletedFiles: map[deletedFileEntry]*fileMetadata{},
}
startLevelBytes := c.startLevel.files.SizeSum()
outputMetrics := &LevelMetrics{
BytesIn: startLevelBytes,
BytesRead: c.outputLevel.files.SizeSum(),
}
if len(c.extraLevels) > 0 {
outputMetrics.BytesIn += c.extraLevels[0].files.SizeSum()
}
outputMetrics.BytesRead += outputMetrics.BytesIn
c.metrics = map[int]*LevelMetrics{
c.outputLevel.level: outputMetrics,
}
if len(c.flushing) == 0 && c.metrics[c.startLevel.level] == nil {
c.metrics[c.startLevel.level] = &LevelMetrics{}
}
if len(c.extraLevels) > 0 {
c.metrics[c.extraLevels[0].level] = &LevelMetrics{}
outputMetrics.MultiLevel.BytesInTop = startLevelBytes
outputMetrics.MultiLevel.BytesIn = outputMetrics.BytesIn
outputMetrics.MultiLevel.BytesRead = outputMetrics.BytesRead
}
// The table is typically written at the maximum allowable format implied by
// the current format major version of the DB.
tableFormat := formatVers.MaxTableFormat()
// In format major versions with maximum table formats of Pebblev3, value
// blocks were conditional on an experimental setting. In format major
// versions with maximum table formats of Pebblev4 and higher, value blocks
// are always enabled.
if tableFormat == sstable.TableFormatPebblev3 &&
(d.opts.Experimental.EnableValueBlocks == nil || !d.opts.Experimental.EnableValueBlocks()) {
tableFormat = sstable.TableFormatPebblev2
}
writerOpts := d.opts.MakeWriterOptions(c.outputLevel.level, tableFormat)
if formatVers < FormatBlockPropertyCollector {
// Cannot yet write block properties.
writerOpts.BlockPropertyCollectors = nil
}
// prevPointKey is a sstable.WriterOption that provides access to
// the last point key written to a writer's sstable. When a new
// output begins in newOutput, prevPointKey is updated to point to
// the new output's sstable.Writer. This allows the compaction loop
// to access the last written point key without requiring the
// compaction loop to make a copy of each key ahead of time. Users
// must be careful, because the byte slice returned by UnsafeKey
// points directly into the Writer's block buffer.
var prevPointKey sstable.PreviousPointKeyOpt
var cpuWorkHandle CPUWorkHandle
defer func() {
if cpuWorkHandle != nil {
d.opts.Experimental.CPUWorkPermissionGranter.CPUWorkDone(cpuWorkHandle)
}
}()
newOutput := func() error {
// Check if we've been cancelled by a concurrent operation.
if c.cancel.Load() {
return ErrCancelledCompaction
}
fileMeta := &fileMetadata{}
d.mu.Lock()
fileNum := d.mu.versions.getNextFileNum()
fileMeta.FileNum = fileNum
pendingOutputs = append(pendingOutputs, fileMeta.PhysicalMeta())
d.mu.Unlock()
ctx := context.TODO()
if objiotracing.Enabled {
ctx = objiotracing.WithLevel(ctx, c.outputLevel.level)
switch c.kind {
case compactionKindFlush:
ctx = objiotracing.WithReason(ctx, objiotracing.ForFlush)
case compactionKindIngestedFlushable:
ctx = objiotracing.WithReason(ctx, objiotracing.ForIngestion)
default:
ctx = objiotracing.WithReason(ctx, objiotracing.ForCompaction)
}
}
// Prefer shared storage if present.
createOpts := objstorage.CreateOptions{
PreferSharedStorage: remote.ShouldCreateShared(d.opts.Experimental.CreateOnShared, c.outputLevel.level),
}
writable, objMeta, err := d.objProvider.Create(ctx, fileTypeTable, fileNum.DiskFileNum(), createOpts)
if err != nil {
return err
}
reason := "flushing"
if c.flushing == nil {
reason = "compacting"
}
d.opts.EventListener.TableCreated(TableCreateInfo{
JobID: jobID,
Reason: reason,
Path: d.objProvider.Path(objMeta),
FileNum: fileNum,
})
if c.kind != compactionKindFlush {
writable = &compactionWritable{
Writable: writable,
versions: d.mu.versions,
written: &c.bytesWritten,
}
}
createdFiles = append(createdFiles, fileNum.DiskFileNum())
cacheOpts := private.SSTableCacheOpts(d.cacheID, fileNum.DiskFileNum()).(sstable.WriterOption)
const MaxFileWriteAdditionalCPUTime = time.Millisecond * 100
cpuWorkHandle = d.opts.Experimental.CPUWorkPermissionGranter.GetPermission(
MaxFileWriteAdditionalCPUTime,
)
writerOpts.Parallelism =
d.opts.Experimental.MaxWriterConcurrency > 0 &&
(cpuWorkHandle.Permitted() || d.opts.Experimental.ForceWriterParallelism)
tw = sstable.NewWriter(writable, writerOpts, cacheOpts, &prevPointKey)
fileMeta.CreationTime = time.Now().Unix()
ve.NewFiles = append(ve.NewFiles, newFileEntry{
Level: c.outputLevel.level,
Meta: fileMeta,
})
return nil
}
// splitL0Outputs is true during flushes and intra-L0 compactions with flush
// splits enabled.
splitL0Outputs := c.outputLevel.level == 0 && d.opts.FlushSplitBytes > 0
// finishOutput is called with the a user key up to which all tombstones
// should be flushed. Typically, this is the first key of the next
// sstable or an empty key if this output is the final sstable.
finishOutput := func(splitKey []byte) error {
// If we haven't output any point records to the sstable (tw == nil) then the
// sstable will only contain range tombstones and/or range keys. The smallest
// key in the sstable will be the start key of the first range tombstone or
// range key added. We need to ensure that this start key is distinct from
// the splitKey passed to finishOutput (if set), otherwise we would generate
// an sstable where the largest key is smaller than the smallest key due to
// how the largest key boundary is set below. NB: It is permissible for the
// range tombstone / range key start key to be the empty string.
//
// TODO: It is unfortunate that we have to do this check here rather than
// when we decide to finish the sstable in the runCompaction loop. A better
// structure currently eludes us.
if tw == nil {
startKey := c.rangeDelFrag.Start()
if len(iter.tombstones) > 0 {
startKey = iter.tombstones[0].Start
}
if startKey == nil {
startKey = c.rangeKeyFrag.Start()
if len(iter.rangeKeys) > 0 {
startKey = iter.rangeKeys[0].Start
}
}
if splitKey != nil && d.cmp(startKey, splitKey) == 0 {
return nil
}
}
// NB: clone the key because the data can be held on to by the call to
// compactionIter.Tombstones via keyspan.Fragmenter.FlushTo, and by the
// WriterMetadata.LargestRangeDel.UserKey.
splitKey = append([]byte(nil), splitKey...)
for _, v := range iter.Tombstones(splitKey) {
if tw == nil {
if err := newOutput(); err != nil {
return err
}
}
// The tombstone being added could be completely outside the
// eventual bounds of the sstable. Consider this example (bounds
// in square brackets next to table filename):
//
// ./000240.sst [tmgc#391,MERGE-tmgc#391,MERGE]
// tmgc#391,MERGE [786e627a]
// tmgc-udkatvs#331,RANGEDEL
//
// ./000241.sst [tmgc#384,MERGE-tmgc#384,MERGE]
// tmgc#384,MERGE [666c7070]
// tmgc-tvsalezade#383,RANGEDEL
// tmgc-tvsalezade#331,RANGEDEL
//
// ./000242.sst [tmgc#383,RANGEDEL-tvsalezade#72057594037927935,RANGEDEL]
// tmgc-tvsalezade#383,RANGEDEL
// tmgc#375,SET [72646c78766965616c72776865676e79]
// tmgc-tvsalezade#356,RANGEDEL
//
// Note that both of the top two SSTables have range tombstones
// that start after the file's end keys. Since the file bound
// computation happens well after all range tombstones have been
// added to the writer, eliding out-of-file range tombstones based
// on sequence number at this stage is difficult, and necessitates
// read-time logic to ignore range tombstones outside file bounds.
if err := rangedel.Encode(&v, tw.Add); err != nil {
return err
}
}
for _, v := range iter.RangeKeys(splitKey) {
// Same logic as for range tombstones, except added using tw.AddRangeKey.
if tw == nil {
if err := newOutput(); err != nil {
return err
}
}
if err := rangekey.Encode(&v, tw.AddRangeKey); err != nil {
return err
}
}
if tw == nil {
return nil
}
{
// Set internal sstable properties.
p := getInternalWriterProperties(tw)
// Set the external sst version to 0. This is what RocksDB expects for
// db-internal sstables; otherwise, it could apply a global sequence number.
p.ExternalFormatVersion = 0
// Set the snapshot pinned totals.
p.SnapshotPinnedKeys = pinnedCount
p.SnapshotPinnedKeySize = pinnedKeySize
p.SnapshotPinnedValueSize = pinnedValueSize
stats.cumulativePinnedKeys += pinnedCount
stats.cumulativePinnedSize += pinnedKeySize + pinnedValueSize
pinnedCount = 0
pinnedKeySize = 0
pinnedValueSize = 0
}
if err := tw.Close(); err != nil {
tw = nil
return err
}
d.opts.Experimental.CPUWorkPermissionGranter.CPUWorkDone(cpuWorkHandle)
cpuWorkHandle = nil
writerMeta, err := tw.Metadata()
if err != nil {
tw = nil
return err
}
tw = nil
meta := ve.NewFiles[len(ve.NewFiles)-1].Meta
meta.Size = writerMeta.Size
meta.SmallestSeqNum = writerMeta.SmallestSeqNum
meta.LargestSeqNum = writerMeta.LargestSeqNum
meta.InitPhysicalBacking()
// If the file didn't contain any range deletions, we can fill its
// table stats now, avoiding unnecessarily loading the table later.
maybeSetStatsFromProperties(
meta.PhysicalMeta(), &writerMeta.Properties,
)
if c.flushing == nil {
outputMetrics.TablesCompacted++
outputMetrics.BytesCompacted += meta.Size
} else {
outputMetrics.TablesFlushed++
outputMetrics.BytesFlushed += meta.Size
}
outputMetrics.Size += int64(meta.Size)
outputMetrics.NumFiles++
outputMetrics.Additional.BytesWrittenDataBlocks += writerMeta.Properties.DataSize
outputMetrics.Additional.BytesWrittenValueBlocks += writerMeta.Properties.ValueBlocksSize
if n := len(ve.NewFiles); n > 1 {
// This is not the first output file. Ensure the sstable boundaries
// are nonoverlapping.
prevMeta := ve.NewFiles[n-2].Meta
if writerMeta.SmallestRangeDel.UserKey != nil {
c := d.cmp(writerMeta.SmallestRangeDel.UserKey, prevMeta.Largest.UserKey)
if c < 0 {
return errors.Errorf(
"pebble: smallest range tombstone start key is less than previous sstable largest key: %s < %s",
writerMeta.SmallestRangeDel.Pretty(d.opts.Comparer.FormatKey),
prevMeta.Largest.Pretty(d.opts.Comparer.FormatKey))
} else if c == 0 && !prevMeta.Largest.IsExclusiveSentinel() {
// The user key portion of the range boundary start key is
// equal to the previous table's largest key user key, and
// the previous table's largest key is not exclusive. This
// violates the invariant that tables are key-space
// partitioned.
return errors.Errorf(
"pebble: invariant violation: previous sstable largest key %s, current sstable smallest rangedel: %s",
prevMeta.Largest.Pretty(d.opts.Comparer.FormatKey),
writerMeta.SmallestRangeDel.Pretty(d.opts.Comparer.FormatKey),
)
}
}
}
// Verify that all range deletions outputted to the sstable are
// truncated to split key.
if splitKey != nil && writerMeta.LargestRangeDel.UserKey != nil &&
d.cmp(writerMeta.LargestRangeDel.UserKey, splitKey) > 0 {
return errors.Errorf(
"pebble: invariant violation: rangedel largest key %q extends beyond split key %q",
writerMeta.LargestRangeDel.Pretty(d.opts.Comparer.FormatKey),
d.opts.Comparer.FormatKey(splitKey),
)
}
if writerMeta.HasPointKeys {
meta.ExtendPointKeyBounds(d.cmp, writerMeta.SmallestPoint, writerMeta.LargestPoint)
}
if writerMeta.HasRangeDelKeys {
meta.ExtendPointKeyBounds(d.cmp, writerMeta.SmallestRangeDel, writerMeta.LargestRangeDel)
}
if writerMeta.HasRangeKeys {
meta.ExtendRangeKeyBounds(d.cmp, writerMeta.SmallestRangeKey, writerMeta.LargestRangeKey)
}
// Verify that the sstable bounds fall within the compaction input
// bounds. This is a sanity check that we don't have a logic error
// elsewhere that causes the sstable bounds to accidentally expand past the
// compaction input bounds as doing so could lead to various badness such
// as keys being deleted by a range tombstone incorrectly.
if c.smallest.UserKey != nil {
switch v := d.cmp(meta.Smallest.UserKey, c.smallest.UserKey); {
case v >= 0:
// Nothing to do.
case v < 0:
return errors.Errorf("pebble: compaction output grew beyond bounds of input: %s < %s",
meta.Smallest.Pretty(d.opts.Comparer.FormatKey),
c.smallest.Pretty(d.opts.Comparer.FormatKey))
}
}
if c.largest.UserKey != nil {
switch v := d.cmp(meta.Largest.UserKey, c.largest.UserKey); {
case v <= 0:
// Nothing to do.
case v > 0:
return errors.Errorf("pebble: compaction output grew beyond bounds of input: %s > %s",
meta.Largest.Pretty(d.opts.Comparer.FormatKey),
c.largest.Pretty(d.opts.Comparer.FormatKey))
}
}
// Verify that we never split different revisions of the same user key
// across two different sstables.
if err := c.errorOnUserKeyOverlap(ve); err != nil {
return err
}
if err := meta.Validate(d.cmp, d.opts.Comparer.FormatKey); err != nil {
return err
}
return nil
}
// Build a compactionOutputSplitter that contains all logic to determine
// whether the compaction loop should stop writing to one output sstable and
// switch to a new one. Some splitters can wrap other splitters, and the
// splitterGroup can be composed of multiple splitters. In this case, we
// start off with splitters for file sizes, grandparent limits, and (for L0
// splits) L0 limits, before wrapping them in an splitterGroup.
sizeSplitter := newFileSizeSplitter(&iter.frontiers, c.maxOutputFileSize, c.grandparents.Iter())
unsafePrevUserKey := func() []byte {
// Return the largest point key written to tw or the start of
// the current range deletion in the fragmenter, whichever is
// greater.
prevPoint := prevPointKey.UnsafeKey()
if c.cmp(prevPoint.UserKey, c.rangeDelFrag.Start()) > 0 {
return prevPoint.UserKey
}
return c.rangeDelFrag.Start()
}
outputSplitters := []compactionOutputSplitter{
// We do not split the same user key across different sstables within
// one flush or compaction. The fileSizeSplitter may request a split in
// the middle of a user key, so the userKeyChangeSplitter ensures we are
// at a user key change boundary when doing a split.
&userKeyChangeSplitter{
cmp: c.cmp,
splitter: sizeSplitter,
unsafePrevUserKey: unsafePrevUserKey,
},
newLimitFuncSplitter(&iter.frontiers, c.findGrandparentLimit),
}
if splitL0Outputs {
outputSplitters = append(outputSplitters, newLimitFuncSplitter(&iter.frontiers, c.findL0Limit))
}
splitter := &splitterGroup{cmp: c.cmp, splitters: outputSplitters}
// Each outer loop iteration produces one output file. An iteration that
// produces a file containing point keys (and optionally range tombstones)
// guarantees that the input iterator advanced. An iteration that produces
// a file containing only range tombstones guarantees the limit passed to
// `finishOutput()` advanced to a strictly greater user key corresponding
// to a grandparent file largest key, or nil. Taken together, these
// progress guarantees ensure that eventually the input iterator will be
// exhausted and the range tombstone fragments will all be flushed.
for key, val := iter.First(); key != nil || !c.rangeDelFrag.Empty() || !c.rangeKeyFrag.Empty(); {
var firstKey []byte
if key != nil {
firstKey = key.UserKey
} else if startKey := c.rangeDelFrag.Start(); startKey != nil {
// Pass the start key of the first pending tombstone to find the
// next limit. All pending tombstones have the same start key. We
// use this as opposed to the end key of the last written sstable to
// effectively handle cases like these:
//
// a.SET.3
// (lf.limit at b)
// d.RANGEDEL.4:f
//
// In this case, the partition after b has only range deletions, so
// if we were to find the limit after the last written key at the
// split point (key a), we'd get the limit b again, and
// finishOutput() would not advance any further because the next
// range tombstone to write does not start until after the L0 split
// point.
firstKey = startKey
}
splitterSuggestion := splitter.onNewOutput(firstKey)
// Each inner loop iteration processes one key from the input iterator.
for ; key != nil; key, val = iter.Next() {
if split := splitter.shouldSplitBefore(key, tw); split == splitNow {
break
}
switch key.Kind() {
case InternalKeyKindRangeDelete:
// Range tombstones are handled specially. They are fragmented,
// and they're not written until later during `finishOutput()`.
// We add them to the `Fragmenter` now to make them visible to
// `compactionIter` so covered keys in the same snapshot stripe
// can be elided.
// The interleaved range deletion might only be one of many with
// these bounds. Some fragmenting is performed ahead of time by
// keyspan.MergingIter.
if s := c.rangeDelIter.Span(); !s.Empty() {
// The memory management here is subtle. Range deletions
// blocks do NOT use prefix compression, which ensures that
// range deletion spans' memory is available as long we keep
// the iterator open. However, the keyspan.MergingIter that
// merges spans across levels only guarantees the lifetime
// of the [start, end) bounds until the next positioning
// method is called.
//
// Additionally, the Span.Keys slice is owned by the the
// range deletion iterator stack, and it may be overwritten
// when we advance.
//
// Clone the Keys slice and the start and end keys.
//
// TODO(jackson): Avoid the clone by removing c.rangeDelFrag
// and performing explicit truncation of the pending
// rangedel span as necessary.
clone := keyspan.Span{
Start: iter.cloneKey(s.Start),
End: iter.cloneKey(s.End),
Keys: make([]keyspan.Key, len(s.Keys)),
}
copy(clone.Keys, s.Keys)
c.rangeDelFrag.Add(clone)
}
continue
case InternalKeyKindRangeKeySet, InternalKeyKindRangeKeyUnset, InternalKeyKindRangeKeyDelete:
// Range keys are handled in the same way as range tombstones, except
// with a dedicated fragmenter.
if s := c.rangeKeyInterleaving.Span(); !s.Empty() {
clone := keyspan.Span{
Start: iter.cloneKey(s.Start),
End: iter.cloneKey(s.End),
Keys: make([]keyspan.Key, len(s.Keys)),
}
// Since the keys' Suffix and Value fields are not deep cloned, the
// underlying blockIter must be kept open for the lifetime of the
// compaction.
copy(clone.Keys, s.Keys)
c.rangeKeyFrag.Add(clone)
}
continue
}
if tw == nil {
if err := newOutput(); err != nil {
return nil, pendingOutputs, stats, err
}
}
if err := tw.AddWithForceObsolete(*key, val, iter.forceObsoleteDueToRangeDel); err != nil {
return nil, pendingOutputs, stats, err
}
if iter.snapshotPinned {
// The kv pair we just added to the sstable was only surfaced by
// the compaction iterator because an open snapshot prevented
// its elision. Increment the stats.
pinnedCount++
pinnedKeySize += uint64(len(key.UserKey)) + base.InternalTrailerLen
pinnedValueSize += uint64(len(val))
}
}
// A splitter requested a split, and we're ready to finish the output.
// We need to choose the key at which to split any pending range
// tombstones. There are two options:
// 1. splitterSuggestion — The key suggested by the splitter. This key
// is guaranteed to be greater than the last key written to the
// current output.
// 2. key.UserKey — the first key of the next sstable output. This user
// key is also guaranteed to be greater than the last user key
// written to the current output (see userKeyChangeSplitter).
//
// Use whichever is smaller. Using the smaller of the two limits
// overlap with grandparents. Consider the case where the
// grandparent limit is calculated to be 'b', key is 'x', and
// there exist many sstables between 'b' and 'x'. If the range
// deletion fragmenter has a pending tombstone [a,x), splitting
// at 'x' would cause the output table to overlap many
// grandparents well beyond the calculated grandparent limit
// 'b'. Splitting at the smaller `splitterSuggestion` avoids
// this unbounded overlap with grandparent tables.
splitKey := splitterSuggestion
if key != nil && (splitKey == nil || c.cmp(splitKey, key.UserKey) > 0) {
splitKey = key.UserKey
}
if err := finishOutput(splitKey); err != nil {
return nil, pendingOutputs, stats, err
}
}
for _, cl := range c.inputs {
iter := cl.files.Iter()
for f := iter.First(); f != nil; f = iter.Next() {
ve.DeletedFiles[deletedFileEntry{
Level: cl.level,
FileNum: f.FileNum,
}] = f
}
}
// The compaction iterator keeps track of a count of the number of DELSIZED
// keys that encoded an incorrect size. Propagate it up as a part of
// compactStats.
stats.countMissizedDels = iter.stats.countMissizedDels
if err := d.objProvider.Sync(); err != nil {
return nil, pendingOutputs, stats, err
}
// Refresh the disk available statistic whenever a compaction/flush
// completes, before re-acquiring the mutex.
_ = d.calculateDiskAvailableBytes()
return ve, pendingOutputs, stats, nil
}
// validateVersionEdit validates that start and end keys across new and deleted
// files in a versionEdit pass the given validation function.
func validateVersionEdit(
ve *versionEdit, validateFn func([]byte) error, format base.FormatKey,
) error {
validateMetaFn := func(f *manifest.FileMetadata) error {
for _, key := range []InternalKey{f.Smallest, f.Largest} {
if err := validateFn(key.UserKey); err != nil {
return errors.Wrapf(err, "key=%q; file=%s", format(key.UserKey), f)
}
}
return nil
}
// Validate both new and deleted files.
for _, f := range ve.NewFiles {
if err := validateMetaFn(f.Meta); err != nil {
return err
}
}
for _, m := range ve.DeletedFiles {
if err := validateMetaFn(m); err != nil {
return err
}
}
return nil
}
// scanObsoleteFiles scans the filesystem for files that are no longer needed
// and adds those to the internal lists of obsolete files. Note that the files
// are not actually deleted by this method. A subsequent call to
// deleteObsoleteFiles must be performed. Must be not be called concurrently
// with compactions and flushes. db.mu must be held when calling this function.
func (d *DB) scanObsoleteFiles(list []string) {
// Disable automatic compactions temporarily to avoid concurrent compactions /
// flushes from interfering. The original value is restored on completion.
disabledPrev := d.opts.DisableAutomaticCompactions
defer func() {
d.opts.DisableAutomaticCompactions = disabledPrev
}()
d.opts.DisableAutomaticCompactions = true
// Wait for any ongoing compaction to complete before continuing.
for d.mu.compact.compactingCount > 0 || d.mu.compact.flushing {
d.mu.compact.cond.Wait()
}
liveFileNums := make(map[base.DiskFileNum]struct{})
d.mu.versions.addLiveFileNums(liveFileNums)
// Protect against files which are only referred to by the ingestedFlushable
// from being deleted. These are added to the flushable queue on WAL replay
// during read only mode and aren't part of the Version. Note that if
// !d.opts.ReadOnly, then all flushables of type ingestedFlushable have
// already been flushed.
for _, fEntry := range d.mu.mem.queue {
if f, ok := fEntry.flushable.(*ingestedFlushable); ok {
for _, file := range f.files {
liveFileNums[file.FileBacking.DiskFileNum] = struct{}{}
}
}
}
minUnflushedLogNum := d.mu.versions.minUnflushedLogNum
manifestFileNum := d.mu.versions.manifestFileNum
var obsoleteLogs []fileInfo
var obsoleteTables []fileInfo
var obsoleteManifests []fileInfo
var obsoleteOptions []fileInfo
for _, filename := range list {
fileType, diskFileNum, ok := base.ParseFilename(d.opts.FS, filename)
if !ok {
continue
}
switch fileType {
case fileTypeLog:
if diskFileNum >= minUnflushedLogNum {
continue
}
fi := fileInfo{fileNum: diskFileNum}
if stat, err := d.opts.FS.Stat(filename); err == nil {
fi.fileSize = uint64(stat.Size())
}
obsoleteLogs = append(obsoleteLogs, fi)
case fileTypeManifest:
if diskFileNum >= manifestFileNum {
continue
}
fi := fileInfo{fileNum: diskFileNum}
if stat, err := d.opts.FS.Stat(filename); err == nil {
fi.fileSize = uint64(stat.Size())
}
obsoleteManifests = append(obsoleteManifests, fi)
case fileTypeOptions:
if diskFileNum.FileNum() >= d.optionsFileNum.FileNum() {
continue
}
fi := fileInfo{fileNum: diskFileNum}
if stat, err := d.opts.FS.Stat(filename); err == nil {
fi.fileSize = uint64(stat.Size())
}
obsoleteOptions = append(obsoleteOptions, fi)
case fileTypeTable:
// Objects are handled through the objstorage provider below.
default:
// Don't delete files we don't know about.
}
}
objects := d.objProvider.List()
for _, obj := range objects {
switch obj.FileType {
case fileTypeTable:
if _, ok := liveFileNums[obj.DiskFileNum]; ok {
continue
}
fileInfo := fileInfo{
fileNum: obj.DiskFileNum,
}
if size, err := d.objProvider.Size(obj); err == nil {
fileInfo.fileSize = uint64(size)
}
obsoleteTables = append(obsoleteTables, fileInfo)
default:
// Ignore object types we don't know about.
}
}
d.mu.log.queue = merge(d.mu.log.queue, obsoleteLogs)
d.mu.versions.metrics.WAL.Files = int64(len(d.mu.log.queue))
d.mu.versions.obsoleteTables = merge(d.mu.versions.obsoleteTables, obsoleteTables)
d.mu.versions.updateObsoleteTableMetricsLocked()
d.mu.versions.obsoleteManifests = merge(d.mu.versions.obsoleteManifests, obsoleteManifests)
d.mu.versions.obsoleteOptions = merge(d.mu.versions.obsoleteOptions, obsoleteOptions)
}
// disableFileDeletions disables file deletions and then waits for any
// in-progress deletion to finish. The caller is required to call
// enableFileDeletions in order to enable file deletions again. It is ok for
// multiple callers to disable file deletions simultaneously, though they must
// all invoke enableFileDeletions in order for file deletions to be re-enabled
// (there is an internal reference count on file deletion disablement).
//
// d.mu must be held when calling this method.
func (d *DB) disableFileDeletions() {
d.mu.disableFileDeletions++
d.mu.Unlock()
defer d.mu.Lock()
d.cleanupManager.Wait()
}
// enableFileDeletions enables previously disabled file deletions. A cleanup job
// is queued if necessary.
//
// d.mu must be held when calling this method.
func (d *DB) enableFileDeletions() {
if d.mu.disableFileDeletions <= 0 {
panic("pebble: file deletion disablement invariant violated")
}
d.mu.disableFileDeletions--
if d.mu.disableFileDeletions > 0 {
return
}
jobID := d.mu.nextJobID
d.mu.nextJobID++
d.deleteObsoleteFiles(jobID)
}
type fileInfo struct {
fileNum base.DiskFileNum
fileSize uint64
}
// deleteObsoleteFiles enqueues a cleanup job to the cleanup manager, if necessary.
//
// d.mu must be held when calling this. The function will release and re-aquire the mutex.
//
// Does nothing if file deletions are disabled (see disableFileDeletions). A
// cleanup job will be scheduled when file deletions are re-enabled.
func (d *DB) deleteObsoleteFiles(jobID int) {
if d.mu.disableFileDeletions > 0 {
return
}
var obsoleteLogs []fileInfo
for i := range d.mu.log.queue {
// NB: d.mu.versions.minUnflushedLogNum is the log number of the earliest
// log that has not had its contents flushed to an sstable. We can recycle
// the prefix of d.mu.log.queue with log numbers less than
// minUnflushedLogNum.
if d.mu.log.queue[i].fileNum >= d.mu.versions.minUnflushedLogNum {
obsoleteLogs = d.mu.log.queue[:i]
d.mu.log.queue = d.mu.log.queue[i:]
d.mu.versions.metrics.WAL.Files -= int64(len(obsoleteLogs))
break
}
}
obsoleteTables := append([]fileInfo(nil), d.mu.versions.obsoleteTables...)
d.mu.versions.obsoleteTables = nil
for _, tbl := range obsoleteTables {
delete(d.mu.versions.zombieTables, tbl.fileNum)
}
// Sort the manifests cause we want to delete some contiguous prefix
// of the older manifests.
slices.SortFunc(d.mu.versions.obsoleteManifests, func(a, b fileInfo) int {
return cmp.Compare(a.fileNum, b.fileNum)
})
var obsoleteManifests []fileInfo
manifestsToDelete := len(d.mu.versions.obsoleteManifests) - d.opts.NumPrevManifest
if manifestsToDelete > 0 {
obsoleteManifests = d.mu.versions.obsoleteManifests[:manifestsToDelete]
d.mu.versions.obsoleteManifests = d.mu.versions.obsoleteManifests[manifestsToDelete:]
if len(d.mu.versions.obsoleteManifests) == 0 {
d.mu.versions.obsoleteManifests = nil
}
}
obsoleteOptions := d.mu.versions.obsoleteOptions
d.mu.versions.obsoleteOptions = nil
// Release d.mu while preparing the cleanup job and possibly waiting.
// Note the unusual order: Unlock and then Lock.
d.mu.Unlock()
defer d.mu.Lock()
files := [4]struct {
fileType fileType
obsolete []fileInfo
}{
{fileTypeLog, obsoleteLogs},
{fileTypeTable, obsoleteTables},
{fileTypeManifest, obsoleteManifests},
{fileTypeOptions, obsoleteOptions},
}
_, noRecycle := d.opts.Cleaner.(base.NeedsFileContents)
filesToDelete := make([]obsoleteFile, 0, len(obsoleteLogs)+len(obsoleteTables)+len(obsoleteManifests)+len(obsoleteOptions))
for _, f := range files {
// We sort to make the order of deletions deterministic, which is nice for
// tests.
slices.SortFunc(f.obsolete, func(a, b fileInfo) int {
return cmp.Compare(a.fileNum, b.fileNum)
})
for _, fi := range f.obsolete {
dir := d.dirname
switch f.fileType {
case fileTypeLog:
if !noRecycle && d.logRecycler.add(fi) {
continue
}
dir = d.walDirname
case fileTypeTable:
d.tableCache.evict(fi.fileNum)
}
filesToDelete = append(filesToDelete, obsoleteFile{
dir: dir,
fileNum: fi.fileNum,
fileType: f.fileType,
fileSize: fi.fileSize,
})
}
}
if len(filesToDelete) > 0 {
d.cleanupManager.EnqueueJob(jobID, filesToDelete)
}
if d.opts.private.testingAlwaysWaitForCleanup {
d.cleanupManager.Wait()
}
}
func (d *DB) maybeScheduleObsoleteTableDeletion() {
d.mu.Lock()
defer d.mu.Unlock()
d.maybeScheduleObsoleteTableDeletionLocked()
}
func (d *DB) maybeScheduleObsoleteTableDeletionLocked() {
if len(d.mu.versions.obsoleteTables) > 0 {
jobID := d.mu.nextJobID
d.mu.nextJobID++
d.deleteObsoleteFiles(jobID)
}
}
func merge(a, b []fileInfo) []fileInfo {
if len(b) == 0 {
return a
}
a = append(a, b...)
slices.SortFunc(a, func(a, b fileInfo) int {
return cmp.Compare(a.fileNum, b.fileNum)
})
return slices.CompactFunc(a, func(a, b fileInfo) bool {
return a.fileNum == b.fileNum
})
}