ceremonyclient/pebble/sstable/reader_iter_single_lvl.go

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2024-01-03 07:31:42 +00:00
// Copyright 2011 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 sstable
import (
"context"
"fmt"
"unsafe"
"github.com/cockroachdb/pebble/internal/base"
"github.com/cockroachdb/pebble/internal/invariants"
"github.com/cockroachdb/pebble/objstorage"
"github.com/cockroachdb/pebble/objstorage/objstorageprovider"
"github.com/cockroachdb/pebble/objstorage/objstorageprovider/objiotracing"
)
// singleLevelIterator iterates over an entire table of data. To seek for a given
// key, it first looks in the index for the block that contains that key, and then
// looks inside that block.
type singleLevelIterator struct {
ctx context.Context
cmp Compare
// Global lower/upper bound for the iterator.
lower []byte
upper []byte
bpfs *BlockPropertiesFilterer
// Per-block lower/upper bound. Nil if the bound does not apply to the block
// because we determined the block lies completely within the bound.
blockLower []byte
blockUpper []byte
reader *Reader
// vState will be set iff the iterator is constructed for virtual sstable
// iteration.
vState *virtualState
// endKeyInclusive is set to force the iterator to treat the upper field as
// inclusive while iterating instead of exclusive.
endKeyInclusive bool
index blockIter
data blockIter
dataRH objstorage.ReadHandle
dataRHPrealloc objstorageprovider.PreallocatedReadHandle
// dataBH refers to the last data block that the iterator considered
// loading. It may not actually have loaded the block, due to an error or
// because it was considered irrelevant.
dataBH BlockHandle
vbReader *valueBlockReader
// vbRH is the read handle for value blocks, which are in a different
// part of the sstable than data blocks.
vbRH objstorage.ReadHandle
vbRHPrealloc objstorageprovider.PreallocatedReadHandle
err error
closeHook func(i Iterator) error
// stats and iterStats are slightly different. stats is a shared struct
// supplied from the outside, and represents stats for the whole iterator
// tree and can be reset from the outside (e.g. when the pebble.Iterator is
// being reused). It is currently only provided when the iterator tree is
// rooted at pebble.Iterator. iterStats is this sstable iterator's private
// stats that are reported to a CategoryStatsCollector when this iterator is
// closed. More paths are instrumented with this as the
// CategoryStatsCollector needed for this is provided by the
// tableCacheContainer (which is more universally used).
stats *base.InternalIteratorStats
iterStats iterStatsAccumulator
bufferPool *BufferPool
// boundsCmp and positionedUsingLatestBounds are for optimizing iteration
// that uses multiple adjacent bounds. The seek after setting a new bound
// can use the fact that the iterator is either within the previous bounds
// or exactly one key before or after the bounds. If the new bounds is
// after/before the previous bounds, and we are already positioned at a
// block that is relevant for the new bounds, we can try to first position
// using Next/Prev (repeatedly) instead of doing a more expensive seek.
//
// When there are wide files at higher levels that match the bounds
// but don't have any data for the bound, we will already be
// positioned at the key beyond the bounds and won't need to do much
// work -- given that most data is in L6, such files are likely to
// dominate the performance of the mergingIter, and may be the main
// benefit of this performance optimization (of course it also helps
// when the file that has the data has successive seeks that stay in
// the same block).
//
// Specifically, boundsCmp captures the relationship between the previous
// and current bounds, if the iterator had been positioned after setting
// the previous bounds. If it was not positioned, i.e., Seek/First/Last
// were not called, we don't know where it is positioned and cannot
// optimize.
//
// Example: Bounds moving forward, and iterator exhausted in forward direction.
// bounds = [f, h), ^ shows block iterator position
// file contents [ a b c d e f g h i j k ]
// ^
// new bounds = [j, k). Since positionedUsingLatestBounds=true, boundsCmp is
// set to +1. SeekGE(j) can use next (the optimization also requires that j
// is within the block, but that is not for correctness, but to limit the
// optimization to when it will actually be an optimization).
//
// Example: Bounds moving forward.
// bounds = [f, h), ^ shows block iterator position
// file contents [ a b c d e f g h i j k ]
// ^
// new bounds = [j, k). Since positionedUsingLatestBounds=true, boundsCmp is
// set to +1. SeekGE(j) can use next.
//
// Example: Bounds moving forward, but iterator not positioned using previous
// bounds.
// bounds = [f, h), ^ shows block iterator position
// file contents [ a b c d e f g h i j k ]
// ^
// new bounds = [i, j). Iterator is at j since it was never positioned using
// [f, h). So positionedUsingLatestBounds=false, and boundsCmp is set to 0.
// SeekGE(i) will not use next.
//
// Example: Bounds moving forward and sparse file
// bounds = [f, h), ^ shows block iterator position
// file contents [ a z ]
// ^
// new bounds = [j, k). Since positionedUsingLatestBounds=true, boundsCmp is
// set to +1. SeekGE(j) notices that the iterator is already past j and does
// not need to do anything.
//
// Similar examples can be constructed for backward iteration.
//
// This notion of exactly one key before or after the bounds is not quite
// true when block properties are used to ignore blocks. In that case we
// can't stop precisely at the first block that is past the bounds since
// we are using the index entries to enforce the bounds.
//
// e.g. 3 blocks with keys [b, c] [f, g], [i, j, k] with index entries d,
// h, l. And let the lower bound be k, and we are reverse iterating. If
// the block [i, j, k] is ignored due to the block interval annotations we
// do need to move the index to block [f, g] since the index entry for the
// [i, j, k] block is l which is not less than the lower bound of k. So we
// have passed the entries i, j.
//
// This behavior is harmless since the block property filters are fixed
// for the lifetime of the iterator so i, j are irrelevant. In addition,
// the current code will not load the [f, g] block, so the seek
// optimization that attempts to use Next/Prev do not apply anyway.
boundsCmp int
positionedUsingLatestBounds bool
// exhaustedBounds represents whether the iterator is exhausted for
// iteration by reaching the upper or lower bound. +1 when exhausted
// the upper bound, -1 when exhausted the lower bound, and 0 when
// neither. exhaustedBounds is also used for the TrySeekUsingNext
// optimization in twoLevelIterator and singleLevelIterator. Care should be
// taken in setting this in twoLevelIterator before calling into
// singleLevelIterator, given that these two iterators share this field.
exhaustedBounds int8
// maybeFilteredKeysSingleLevel indicates whether the last iterator
// positioning operation may have skipped any data blocks due to
// block-property filters when positioning the index.
maybeFilteredKeysSingleLevel bool
// useFilter specifies whether the filter block in this sstable, if present,
// should be used for prefix seeks or not. In some cases it is beneficial
// to skip a filter block even if it exists (eg. if probability of a match
// is high).
useFilter bool
lastBloomFilterMatched bool
hideObsoletePoints bool
}
// singleLevelIterator implements the base.InternalIterator interface.
var _ base.InternalIterator = (*singleLevelIterator)(nil)
// init initializes a singleLevelIterator for reading from the table. It is
// synonmous with Reader.NewIter, but allows for reusing of the iterator
// between different Readers.
//
// Note that lower, upper passed into init has nothing to do with virtual sstable
// bounds. If the virtualState passed in is not nil, then virtual sstable bounds
// will be enforced.
func (i *singleLevelIterator) init(
ctx context.Context,
r *Reader,
v *virtualState,
lower, upper []byte,
filterer *BlockPropertiesFilterer,
useFilter, hideObsoletePoints bool,
stats *base.InternalIteratorStats,
categoryAndQoS CategoryAndQoS,
statsCollector *CategoryStatsCollector,
rp ReaderProvider,
bufferPool *BufferPool,
) error {
if r.err != nil {
return r.err
}
i.iterStats.init(categoryAndQoS, statsCollector)
indexH, err := r.readIndex(ctx, stats, &i.iterStats)
if err != nil {
return err
}
if v != nil {
i.vState = v
i.endKeyInclusive, lower, upper = v.constrainBounds(lower, upper, false /* endInclusive */)
}
i.ctx = ctx
i.lower = lower
i.upper = upper
i.bpfs = filterer
i.useFilter = useFilter
i.reader = r
i.cmp = r.Compare
i.stats = stats
i.hideObsoletePoints = hideObsoletePoints
i.bufferPool = bufferPool
err = i.index.initHandle(i.cmp, indexH, r.Properties.GlobalSeqNum, false)
if err != nil {
// blockIter.Close releases indexH and always returns a nil error
_ = i.index.Close()
return err
}
i.dataRH = objstorageprovider.UsePreallocatedReadHandle(ctx, r.readable, &i.dataRHPrealloc)
if r.tableFormat >= TableFormatPebblev3 {
if r.Properties.NumValueBlocks > 0 {
// NB: we cannot avoid this ~248 byte allocation, since valueBlockReader
// can outlive the singleLevelIterator due to be being embedded in a
// LazyValue. This consumes ~2% in microbenchmark CPU profiles, but we
// should only optimize this if it shows up as significant in end-to-end
// CockroachDB benchmarks, since it is tricky to do so. One possibility
// is that if many sstable iterators only get positioned at latest
// versions of keys, and therefore never expose a LazyValue that is
// separated to their callers, they can put this valueBlockReader into a
// sync.Pool.
i.vbReader = &valueBlockReader{
bpOpen: i,
rp: rp,
vbih: r.valueBIH,
stats: stats,
}
i.data.lazyValueHandling.vbr = i.vbReader
i.vbRH = objstorageprovider.UsePreallocatedReadHandle(ctx, r.readable, &i.vbRHPrealloc)
}
i.data.lazyValueHandling.hasValuePrefix = true
}
return nil
}
// Helper function to check if keys returned from iterator are within global and virtual bounds.
func (i *singleLevelIterator) maybeVerifyKey(
iKey *InternalKey, val base.LazyValue,
) (*InternalKey, base.LazyValue) {
// maybeVerify key is only used for virtual sstable iterators.
if invariants.Enabled && i.vState != nil && iKey != nil {
key := iKey.UserKey
uc, vuc := i.cmp(key, i.upper), i.cmp(key, i.vState.upper.UserKey)
lc, vlc := i.cmp(key, i.lower), i.cmp(key, i.vState.lower.UserKey)
if (i.vState.upper.IsExclusiveSentinel() && vuc == 0) || (!i.endKeyInclusive && uc == 0) || uc > 0 || vuc > 0 || lc < 0 || vlc < 0 {
panic(fmt.Sprintf("key: %s out of bounds of singleLevelIterator", key))
}
}
return iKey, val
}
// setupForCompaction sets up the singleLevelIterator for use with compactionIter.
// Currently, it skips readahead ramp-up. It should be called after init is called.
func (i *singleLevelIterator) setupForCompaction() {
i.dataRH.SetupForCompaction()
if i.vbRH != nil {
i.vbRH.SetupForCompaction()
}
}
func (i *singleLevelIterator) resetForReuse() singleLevelIterator {
return singleLevelIterator{
index: i.index.resetForReuse(),
data: i.data.resetForReuse(),
}
}
func (i *singleLevelIterator) initBounds() {
// Trim the iteration bounds for the current block. We don't have to check
// the bounds on each iteration if the block is entirely contained within the
// iteration bounds.
i.blockLower = i.lower
if i.blockLower != nil {
key, _ := i.data.First()
if key != nil && i.cmp(i.blockLower, key.UserKey) < 0 {
// The lower-bound is less than the first key in the block. No need
// to check the lower-bound again for this block.
i.blockLower = nil
}
}
i.blockUpper = i.upper
if i.blockUpper != nil && i.cmp(i.blockUpper, i.index.Key().UserKey) > 0 {
// The upper-bound is greater than the index key which itself is greater
// than or equal to every key in the block. No need to check the
// upper-bound again for this block. Even if blockUpper is inclusive
// because of upper being inclusive, we can still safely set blockUpper
// to nil here.
//
// TODO(bananabrick): We could also set blockUpper to nil for the >=
// case, if blockUpper is inclusive.
i.blockUpper = nil
}
}
// Deterministic disabling of the bounds-based optimization that avoids seeking.
// Uses the iterator pointer, since we want diversity in iterator behavior for
// the same SetBounds call. Used for tests.
func disableBoundsOpt(bound []byte, ptr uintptr) bool {
// Fibonacci hash https://probablydance.com/2018/06/16/fibonacci-hashing-the-optimization-that-the-world-forgot-or-a-better-alternative-to-integer-modulo/
simpleHash := (11400714819323198485 * uint64(ptr)) >> 63
return bound[len(bound)-1]&byte(1) == 0 && simpleHash == 0
}
// ensureBoundsOptDeterminism provides a facility for disabling of the bounds
// optimizations performed by disableBoundsOpt for tests that require
// deterministic iterator behavior. Some unit tests examine internal iterator
// state and require this behavior to be deterministic.
var ensureBoundsOptDeterminism bool
// SetBounds implements internalIterator.SetBounds, as documented in the pebble
// package. Note that the upper field is exclusive.
func (i *singleLevelIterator) SetBounds(lower, upper []byte) {
i.boundsCmp = 0
if i.vState != nil {
// If the reader is constructed for a virtual sstable, then we must
// constrain the bounds of the reader. For physical sstables, the bounds
// can be wider than the actual sstable's bounds because we won't
// accidentally expose additional keys as there are no additional keys.
i.endKeyInclusive, lower, upper = i.vState.constrainBounds(
lower, upper, false,
)
} else {
// TODO(bananabrick): Figure out the logic here to enable the boundsCmp
// optimization for virtual sstables.
if i.positionedUsingLatestBounds {
if i.upper != nil && lower != nil && i.cmp(i.upper, lower) <= 0 {
i.boundsCmp = +1
if invariants.Enabled && !ensureBoundsOptDeterminism &&
disableBoundsOpt(lower, uintptr(unsafe.Pointer(i))) {
i.boundsCmp = 0
}
} else if i.lower != nil && upper != nil && i.cmp(upper, i.lower) <= 0 {
i.boundsCmp = -1
if invariants.Enabled && !ensureBoundsOptDeterminism &&
disableBoundsOpt(upper, uintptr(unsafe.Pointer(i))) {
i.boundsCmp = 0
}
}
}
}
i.positionedUsingLatestBounds = false
i.lower = lower
i.upper = upper
i.blockLower = nil
i.blockUpper = nil
}
func (i *singleLevelIterator) SetContext(ctx context.Context) {
i.ctx = ctx
}
// loadBlock loads the block at the current index position and leaves i.data
// unpositioned. If unsuccessful, it sets i.err to any error encountered, which
// may be nil if we have simply exhausted the entire table.
func (i *singleLevelIterator) loadBlock(dir int8) loadBlockResult {
if !i.index.valid() {
// Ensure the data block iterator is invalidated even if loading of the block
// fails.
i.data.invalidate()
return loadBlockFailed
}
// Load the next block.
v := i.index.value()
bhp, err := decodeBlockHandleWithProperties(v.InPlaceValue())
if i.dataBH == bhp.BlockHandle && i.data.valid() {
// We're already at the data block we want to load. Reset bounds in case
// they changed since the last seek, but don't reload the block from cache
// or disk.
//
// It's safe to leave i.data in its original state here, as all callers to
// loadBlock make an absolute positioning call (i.e. a seek, first, or last)
// to `i.data` right after loadBlock returns loadBlockOK.
i.initBounds()
return loadBlockOK
}
// Ensure the data block iterator is invalidated even if loading of the block
// fails.
i.data.invalidate()
i.dataBH = bhp.BlockHandle
if err != nil {
i.err = errCorruptIndexEntry
return loadBlockFailed
}
if i.bpfs != nil {
intersects, err := i.bpfs.intersects(bhp.Props)
if err != nil {
i.err = errCorruptIndexEntry
return loadBlockFailed
}
if intersects == blockMaybeExcluded {
intersects = i.resolveMaybeExcluded(dir)
}
if intersects == blockExcluded {
i.maybeFilteredKeysSingleLevel = true
return loadBlockIrrelevant
}
// blockIntersects
}
ctx := objiotracing.WithBlockType(i.ctx, objiotracing.DataBlock)
block, err := i.reader.readBlock(
ctx, i.dataBH, nil /* transform */, i.dataRH, i.stats, &i.iterStats, i.bufferPool)
if err != nil {
i.err = err
return loadBlockFailed
}
i.err = i.data.initHandle(i.cmp, block, i.reader.Properties.GlobalSeqNum, i.hideObsoletePoints)
if i.err != nil {
// The block is partially loaded, and we don't want it to appear valid.
i.data.invalidate()
return loadBlockFailed
}
i.initBounds()
return loadBlockOK
}
// readBlockForVBR implements the blockProviderWhenOpen interface for use by
// the valueBlockReader.
func (i *singleLevelIterator) readBlockForVBR(
h BlockHandle, stats *base.InternalIteratorStats,
) (bufferHandle, error) {
ctx := objiotracing.WithBlockType(i.ctx, objiotracing.ValueBlock)
return i.reader.readBlock(ctx, h, nil, i.vbRH, stats, &i.iterStats, i.bufferPool)
}
// resolveMaybeExcluded is invoked when the block-property filterer has found
// that a block is excluded according to its properties but only if its bounds
// fall within the filter's current bounds. This function consults the
// apprioriate bound, depending on the iteration direction, and returns either
// `blockIntersects` or `blockMaybeExcluded`.
func (i *singleLevelIterator) resolveMaybeExcluded(dir int8) intersectsResult {
// TODO(jackson): We could first try comparing to top-level index block's
// key, and if within bounds avoid per-data block key comparisons.
// This iterator is configured with a bound-limited block property
// filter. The bpf determined this block could be excluded from
// iteration based on the property encoded in the block handle.
// However, we still need to determine if the block is wholly
// contained within the filter's key bounds.
//
// External guarantees ensure all the block's keys are ≥ the
// filter's lower bound during forward iteration, and that all the
// block's keys are < the filter's upper bound during backward
// iteration. We only need to determine if the opposite bound is
// also met.
//
// The index separator in index.Key() provides an inclusive
// upper-bound for the data block's keys, guaranteeing that all its
// keys are ≤ index.Key(). For forward iteration, this is all we
// need.
if dir > 0 {
// Forward iteration.
if i.bpfs.boundLimitedFilter.KeyIsWithinUpperBound(i.index.Key().UserKey) {
return blockExcluded
}
return blockIntersects
}
// Reverse iteration.
//
// Because we're iterating in the reverse direction, we don't yet have
// enough context available to determine if the block is wholly contained
// within its bounds. This case arises only during backward iteration,
// because of the way the index is structured.
//
// Consider a bound-limited bpf limited to the bounds [b,d), loading the
// block with separator `c`. During reverse iteration, the guarantee that
// all the block's keys are < `d` is externally provided, but no guarantee
// is made on the bpf's lower bound. The separator `c` only provides an
// inclusive upper bound on the block's keys, indicating that the
// corresponding block handle points to a block containing only keys ≤ `c`.
//
// To establish a lower bound, we step the index backwards to read the
// previous block's separator, which provides an inclusive lower bound on
// the original block's keys. Afterwards, we step forward to restore our
// index position.
if peekKey, _ := i.index.Prev(); peekKey == nil {
// The original block points to the first block of this index block. If
// there's a two-level index, it could potentially provide a lower
// bound, but the code refactoring necessary to read it doesn't seem
// worth the payoff. We fall through to loading the block.
} else if i.bpfs.boundLimitedFilter.KeyIsWithinLowerBound(peekKey.UserKey) {
// The lower-bound on the original block falls within the filter's
// bounds, and we can skip the block (after restoring our current index
// position).
_, _ = i.index.Next()
return blockExcluded
}
_, _ = i.index.Next()
return blockIntersects
}
func (i *singleLevelIterator) initBoundsForAlreadyLoadedBlock() {
if i.data.getFirstUserKey() == nil {
panic("initBoundsForAlreadyLoadedBlock must not be called on empty or corrupted block")
}
i.blockLower = i.lower
if i.blockLower != nil {
firstUserKey := i.data.getFirstUserKey()
if firstUserKey != nil && i.cmp(i.blockLower, firstUserKey) < 0 {
// The lower-bound is less than the first key in the block. No need
// to check the lower-bound again for this block.
i.blockLower = nil
}
}
i.blockUpper = i.upper
if i.blockUpper != nil && i.cmp(i.blockUpper, i.index.Key().UserKey) > 0 {
// The upper-bound is greater than the index key which itself is greater
// than or equal to every key in the block. No need to check the
// upper-bound again for this block.
i.blockUpper = nil
}
}
// The number of times to call Next/Prev in a block before giving up and seeking.
// The value of 4 is arbitrary.
// TODO(sumeer): experiment with dynamic adjustment based on the history of
// seeks for a particular iterator.
const numStepsBeforeSeek = 4
func (i *singleLevelIterator) trySeekGEUsingNextWithinBlock(
key []byte,
) (k *InternalKey, v base.LazyValue, done bool) {
k, v = i.data.Key(), i.data.value()
for j := 0; j < numStepsBeforeSeek; j++ {
curKeyCmp := i.cmp(k.UserKey, key)
if curKeyCmp >= 0 {
if i.blockUpper != nil {
cmp := i.cmp(k.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}, true
}
}
return k, v, true
}
k, v = i.data.Next()
if k == nil {
break
}
}
return k, v, false
}
func (i *singleLevelIterator) trySeekLTUsingPrevWithinBlock(
key []byte,
) (k *InternalKey, v base.LazyValue, done bool) {
k, v = i.data.Key(), i.data.value()
for j := 0; j < numStepsBeforeSeek; j++ {
curKeyCmp := i.cmp(k.UserKey, key)
if curKeyCmp < 0 {
if i.blockLower != nil && i.cmp(k.UserKey, i.blockLower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}, true
}
return k, v, true
}
k, v = i.data.Prev()
if k == nil {
break
}
}
return k, v, false
}
func (i *singleLevelIterator) recordOffset() uint64 {
offset := i.dataBH.Offset
if i.data.valid() {
// - i.dataBH.Length/len(i.data.data) is the compression ratio. If
// uncompressed, this is 1.
// - i.data.nextOffset is the uncompressed position of the current record
// in the block.
// - i.dataBH.Offset is the offset of the block in the sstable before
// decompression.
offset += (uint64(i.data.nextOffset) * i.dataBH.Length) / uint64(len(i.data.data))
} else {
// Last entry in the block must increment bytes iterated by the size of the block trailer
// and restart points.
offset += i.dataBH.Length + blockTrailerLen
}
return offset
}
// SeekGE implements internalIterator.SeekGE, as documented in the pebble
// package. Note that SeekGE only checks the upper bound. It is up to the
// caller to ensure that key is greater than or equal to the lower bound.
func (i *singleLevelIterator) SeekGE(
key []byte, flags base.SeekGEFlags,
) (*InternalKey, base.LazyValue) {
if i.vState != nil {
// Callers of SeekGE don't know about virtual sstable bounds, so we may
// have to internally restrict the bounds.
//
// TODO(bananabrick): We can optimize this check away for the level iter
// if necessary.
if i.cmp(key, i.lower) < 0 {
key = i.lower
}
}
if flags.TrySeekUsingNext() {
// The i.exhaustedBounds comparison indicates that the upper bound was
// reached. The i.data.isDataInvalidated() indicates that the sstable was
// exhausted.
if (i.exhaustedBounds == +1 || i.data.isDataInvalidated()) && i.err == nil {
// Already exhausted, so return nil.
return nil, base.LazyValue{}
}
if i.err != nil {
// The current iterator position cannot be used.
flags = flags.DisableTrySeekUsingNext()
}
// INVARIANT: flags.TrySeekUsingNext() => i.err == nil &&
// !i.exhaustedBounds==+1 && !i.data.isDataInvalidated(). That is,
// data-exhausted and bounds-exhausted, as defined earlier, are both
// false. Ths makes it safe to clear out i.exhaustedBounds and i.err
// before calling into seekGEHelper.
}
i.exhaustedBounds = 0
i.err = nil // clear cached iteration error
boundsCmp := i.boundsCmp
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
i.positionedUsingLatestBounds = true
return i.seekGEHelper(key, boundsCmp, flags)
}
// seekGEHelper contains the common functionality for SeekGE and SeekPrefixGE.
func (i *singleLevelIterator) seekGEHelper(
key []byte, boundsCmp int, flags base.SeekGEFlags,
) (*InternalKey, base.LazyValue) {
// Invariant: trySeekUsingNext => !i.data.isDataInvalidated() && i.exhaustedBounds != +1
// SeekGE performs various step-instead-of-seeking optimizations: eg enabled
// by trySeekUsingNext, or by monotonically increasing bounds (i.boundsCmp).
// Care must be taken to ensure that when performing these optimizations and
// the iterator becomes exhausted, i.maybeFilteredKeys is set appropriately.
// Consider a previous SeekGE that filtered keys from k until the current
// iterator position.
//
// If the previous SeekGE exhausted the iterator, it's possible keys greater
// than or equal to the current search key were filtered. We must not reuse
// the current iterator position without remembering the previous value of
// maybeFilteredKeys.
var dontSeekWithinBlock bool
if !i.data.isDataInvalidated() && !i.index.isDataInvalidated() && i.data.valid() && i.index.valid() &&
boundsCmp > 0 && i.cmp(key, i.index.Key().UserKey) <= 0 {
// Fast-path: The bounds have moved forward and this SeekGE is
// respecting the lower bound (guaranteed by Iterator). We know that
// the iterator must already be positioned within or just outside the
// previous bounds. Therefore it cannot be positioned at a block (or
// the position within that block) that is ahead of the seek position.
// However it can be positioned at an earlier block. This fast-path to
// use Next() on the block is only applied when we are already at the
// block that the slow-path (the else-clause) would load -- this is
// the motivation for the i.cmp(key, i.index.Key().UserKey) <= 0
// predicate.
i.initBoundsForAlreadyLoadedBlock()
ikey, val, done := i.trySeekGEUsingNextWithinBlock(key)
if done {
return ikey, val
}
if ikey == nil {
// Done with this block.
dontSeekWithinBlock = true
}
} else {
// Cannot use bounds monotonicity. But may be able to optimize if
// caller claimed externally known invariant represented by
// flags.TrySeekUsingNext().
if flags.TrySeekUsingNext() {
// seekPrefixGE or SeekGE has already ensured
// !i.data.isDataInvalidated() && i.exhaustedBounds != +1
currKey := i.data.Key()
value := i.data.value()
less := i.cmp(currKey.UserKey, key) < 0
// We could be more sophisticated and confirm that the seek
// position is within the current block before applying this
// optimization. But there may be some benefit even if it is in
// the next block, since we can avoid seeking i.index.
for j := 0; less && j < numStepsBeforeSeek; j++ {
currKey, value = i.Next()
if currKey == nil {
return nil, base.LazyValue{}
}
less = i.cmp(currKey.UserKey, key) < 0
}
if !less {
if i.blockUpper != nil {
cmp := i.cmp(currKey.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return currKey, value
}
}
// Slow-path.
// Since we're re-seeking the iterator, the previous value of
// maybeFilteredKeysSingleLevel is irrelevant. If we filter out blocks
// during seeking, loadBlock will set it to true.
i.maybeFilteredKeysSingleLevel = false
var ikey *InternalKey
if ikey, _ = i.index.SeekGE(key, flags.DisableTrySeekUsingNext()); ikey == nil {
// The target key is greater than any key in the index block.
// Invalidate the block iterator so that a subsequent call to Prev()
// will return the last key in the table.
i.data.invalidate()
return nil, base.LazyValue{}
}
result := i.loadBlock(+1)
if result == loadBlockFailed {
return nil, base.LazyValue{}
}
if result == loadBlockIrrelevant {
// Enforce the upper bound here since don't want to bother moving
// to the next block if upper bound is already exceeded. Note that
// the next block starts with keys >= ikey.UserKey since even
// though this is the block separator, the same user key can span
// multiple blocks. If upper is exclusive we use >= below, else
// we use >.
if i.upper != nil {
cmp := i.cmp(ikey.UserKey, i.upper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
// Want to skip to the next block.
dontSeekWithinBlock = true
}
}
if !dontSeekWithinBlock {
if ikey, val := i.data.SeekGE(key, flags.DisableTrySeekUsingNext()); ikey != nil {
if i.blockUpper != nil {
cmp := i.cmp(ikey.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return ikey, val
}
}
return i.skipForward()
}
// SeekPrefixGE implements internalIterator.SeekPrefixGE, as documented in the
// pebble package. Note that SeekPrefixGE only checks the upper bound. It is up
// to the caller to ensure that key is greater than or equal to the lower bound.
func (i *singleLevelIterator) SeekPrefixGE(
prefix, key []byte, flags base.SeekGEFlags,
) (*base.InternalKey, base.LazyValue) {
if i.vState != nil {
// Callers of SeekPrefixGE aren't aware of virtual sstable bounds, so
// we may have to internally restrict the bounds.
//
// TODO(bananabrick): We can optimize away this check for the level iter
// if necessary.
if i.cmp(key, i.lower) < 0 {
key = i.lower
}
}
return i.seekPrefixGE(prefix, key, flags, i.useFilter)
}
func (i *singleLevelIterator) seekPrefixGE(
prefix, key []byte, flags base.SeekGEFlags, checkFilter bool,
) (k *InternalKey, value base.LazyValue) {
// NOTE: prefix is only used for bloom filter checking and not later work in
// this method. Hence, we can use the existing iterator position if the last
// SeekPrefixGE did not fail bloom filter matching.
err := i.err
i.err = nil // clear cached iteration error
if checkFilter && i.reader.tableFilter != nil {
if !i.lastBloomFilterMatched {
// Iterator is not positioned based on last seek.
flags = flags.DisableTrySeekUsingNext()
}
i.lastBloomFilterMatched = false
// Check prefix bloom filter.
var dataH bufferHandle
dataH, i.err = i.reader.readFilter(i.ctx, i.stats, &i.iterStats)
if i.err != nil {
i.data.invalidate()
return nil, base.LazyValue{}
}
mayContain := i.reader.tableFilter.mayContain(dataH.Get(), prefix)
dataH.Release()
if !mayContain {
// This invalidation may not be necessary for correctness, and may
// be a place to optimize later by reusing the already loaded
// block. It was necessary in earlier versions of the code since
// the caller was allowed to call Next when SeekPrefixGE returned
// nil. This is no longer allowed.
i.data.invalidate()
return nil, base.LazyValue{}
}
i.lastBloomFilterMatched = true
}
if flags.TrySeekUsingNext() {
// The i.exhaustedBounds comparison indicates that the upper bound was
// reached. The i.data.isDataInvalidated() indicates that the sstable was
// exhausted.
if (i.exhaustedBounds == +1 || i.data.isDataInvalidated()) && err == nil {
// Already exhausted, so return nil.
return nil, base.LazyValue{}
}
if err != nil {
// The current iterator position cannot be used.
flags = flags.DisableTrySeekUsingNext()
}
// INVARIANT: flags.TrySeekUsingNext() => err == nil &&
// !i.exhaustedBounds==+1 && !i.data.isDataInvalidated(). That is,
// data-exhausted and bounds-exhausted, as defined earlier, are both
// false. Ths makes it safe to clear out i.exhaustedBounds and i.err
// before calling into seekGEHelper.
}
// Bloom filter matches, or skipped, so this method will position the
// iterator.
i.exhaustedBounds = 0
boundsCmp := i.boundsCmp
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
i.positionedUsingLatestBounds = true
k, value = i.seekGEHelper(key, boundsCmp, flags)
return i.maybeVerifyKey(k, value)
}
// virtualLast should only be called if i.vReader != nil.
func (i *singleLevelIterator) virtualLast() (*InternalKey, base.LazyValue) {
if i.vState == nil {
panic("pebble: invalid call to virtualLast")
}
// Seek to the first internal key.
ikey, _ := i.SeekGE(i.upper, base.SeekGEFlagsNone)
if i.endKeyInclusive {
// Let's say the virtual sstable upper bound is c#1, with the keys c#3, c#2,
// c#1, d, e, ... in the sstable. So, the last key in the virtual sstable is
// c#1. We can perform SeekGE(i.upper) and then keep nexting until we find
// the last key with userkey == i.upper.
//
// TODO(bananabrick): Think about how to improve this. If many internal keys
// with the same user key at the upper bound then this could be slow, but
// maybe the odds of having many internal keys with the same user key at the
// upper bound are low.
for ikey != nil && i.cmp(ikey.UserKey, i.upper) == 0 {
ikey, _ = i.Next()
}
return i.Prev()
}
// We seeked to the first key >= i.upper.
return i.Prev()
}
// SeekLT implements internalIterator.SeekLT, as documented in the pebble
// package. Note that SeekLT only checks the lower bound. It is up to the
// caller to ensure that key is less than or equal to the upper bound.
func (i *singleLevelIterator) SeekLT(
key []byte, flags base.SeekLTFlags,
) (*InternalKey, base.LazyValue) {
if i.vState != nil {
// Might have to fix upper bound since virtual sstable bounds are not
// known to callers of SeekLT.
//
// TODO(bananabrick): We can optimize away this check for the level iter
// if necessary.
cmp := i.cmp(key, i.upper)
// key == i.upper is fine. We'll do the right thing and return the
// first internal key with user key < key.
if cmp > 0 {
// Return the last key in the virtual sstable.
return i.virtualLast()
}
}
i.exhaustedBounds = 0
i.err = nil // clear cached iteration error
boundsCmp := i.boundsCmp
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
// Seeking operations perform various step-instead-of-seeking optimizations:
// eg by considering monotonically increasing bounds (i.boundsCmp). Care
// must be taken to ensure that when performing these optimizations and the
// iterator becomes exhausted i.maybeFilteredKeysSingleLevel is set
// appropriately. Consider a previous SeekLT that filtered keys from k
// until the current iterator position.
//
// If the previous SeekLT did exhausted the iterator, it's possible keys
// less than the current search key were filtered. We must not reuse the
// current iterator position without remembering the previous value of
// maybeFilteredKeysSingleLevel.
i.positionedUsingLatestBounds = true
var dontSeekWithinBlock bool
if !i.data.isDataInvalidated() && !i.index.isDataInvalidated() && i.data.valid() && i.index.valid() &&
boundsCmp < 0 && i.cmp(i.data.getFirstUserKey(), key) < 0 {
// Fast-path: The bounds have moved backward, and this SeekLT is
// respecting the upper bound (guaranteed by Iterator). We know that
// the iterator must already be positioned within or just outside the
// previous bounds. Therefore it cannot be positioned at a block (or
// the position within that block) that is behind the seek position.
// However it can be positioned at a later block. This fast-path to
// use Prev() on the block is only applied when we are already at the
// block that can satisfy this seek -- this is the motivation for the
// the i.cmp(i.data.firstKey.UserKey, key) < 0 predicate.
i.initBoundsForAlreadyLoadedBlock()
ikey, val, done := i.trySeekLTUsingPrevWithinBlock(key)
if done {
return ikey, val
}
if ikey == nil {
// Done with this block.
dontSeekWithinBlock = true
}
} else {
// Slow-path.
i.maybeFilteredKeysSingleLevel = false
var ikey *InternalKey
// NB: If a bound-limited block property filter is configured, it's
// externally ensured that the filter is disabled (through returning
// Intersects=false irrespective of the block props provided) during
// seeks.
if ikey, _ = i.index.SeekGE(key, base.SeekGEFlagsNone); ikey == nil {
ikey, _ = i.index.Last()
if ikey == nil {
return nil, base.LazyValue{}
}
}
// INVARIANT: ikey != nil.
result := i.loadBlock(-1)
if result == loadBlockFailed {
return nil, base.LazyValue{}
}
if result == loadBlockIrrelevant {
// Enforce the lower bound here since don't want to bother moving
// to the previous block if lower bound is already exceeded. Note
// that the previous block starts with keys <= ikey.UserKey since
// even though this is the current block's separator, the same
// user key can span multiple blocks.
if i.lower != nil && i.cmp(ikey.UserKey, i.lower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
// Want to skip to the previous block.
dontSeekWithinBlock = true
}
}
if !dontSeekWithinBlock {
if ikey, val := i.data.SeekLT(key, flags); ikey != nil {
if i.blockLower != nil && i.cmp(ikey.UserKey, i.blockLower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
return ikey, val
}
}
// The index contains separator keys which may lie between
// user-keys. Consider the user-keys:
//
// complete
// ---- new block ---
// complexion
//
// If these two keys end one block and start the next, the index key may
// be chosen as "compleu". The SeekGE in the index block will then point
// us to the block containing "complexion". If this happens, we want the
// last key from the previous data block.
return i.maybeVerifyKey(i.skipBackward())
}
// First implements internalIterator.First, as documented in the pebble
// package. Note that First only checks the upper bound. It is up to the caller
// to ensure that key is greater than or equal to the lower bound (e.g. via a
// call to SeekGE(lower)).
func (i *singleLevelIterator) First() (*InternalKey, base.LazyValue) {
// If the iterator was created on a virtual sstable, we will SeekGE to the
// lower bound instead of using First, because First does not respect
// bounds.
if i.vState != nil {
return i.SeekGE(i.lower, base.SeekGEFlagsNone)
}
if i.lower != nil {
panic("singleLevelIterator.First() used despite lower bound")
}
i.positionedUsingLatestBounds = true
i.maybeFilteredKeysSingleLevel = false
return i.firstInternal()
}
// firstInternal is a helper used for absolute positioning in a single-level
// index file, or for positioning in the second-level index in a two-level
// index file. For the latter, one cannot make any claims about absolute
// positioning.
func (i *singleLevelIterator) firstInternal() (*InternalKey, base.LazyValue) {
i.exhaustedBounds = 0
i.err = nil // clear cached iteration error
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
var ikey *InternalKey
if ikey, _ = i.index.First(); ikey == nil {
i.data.invalidate()
return nil, base.LazyValue{}
}
result := i.loadBlock(+1)
if result == loadBlockFailed {
return nil, base.LazyValue{}
}
if result == loadBlockOK {
if ikey, val := i.data.First(); ikey != nil {
if i.blockUpper != nil {
cmp := i.cmp(ikey.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return ikey, val
}
// Else fall through to skipForward.
} else {
// result == loadBlockIrrelevant. Enforce the upper bound here since
// don't want to bother moving to the next block if upper bound is
// already exceeded. Note that the next block starts with keys >=
// ikey.UserKey since even though this is the block separator, the
// same user key can span multiple blocks. If upper is exclusive we
// use >= below, else we use >.
if i.upper != nil {
cmp := i.cmp(ikey.UserKey, i.upper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
// Else fall through to skipForward.
}
return i.skipForward()
}
// Last implements internalIterator.Last, as documented in the pebble
// package. Note that Last only checks the lower bound. It is up to the caller
// to ensure that key is less than the upper bound (e.g. via a call to
// SeekLT(upper))
func (i *singleLevelIterator) Last() (*InternalKey, base.LazyValue) {
if i.vState != nil {
return i.virtualLast()
}
if i.upper != nil {
panic("singleLevelIterator.Last() used despite upper bound")
}
i.positionedUsingLatestBounds = true
i.maybeFilteredKeysSingleLevel = false
return i.lastInternal()
}
// lastInternal is a helper used for absolute positioning in a single-level
// index file, or for positioning in the second-level index in a two-level
// index file. For the latter, one cannot make any claims about absolute
// positioning.
func (i *singleLevelIterator) lastInternal() (*InternalKey, base.LazyValue) {
i.exhaustedBounds = 0
i.err = nil // clear cached iteration error
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
var ikey *InternalKey
if ikey, _ = i.index.Last(); ikey == nil {
i.data.invalidate()
return nil, base.LazyValue{}
}
result := i.loadBlock(-1)
if result == loadBlockFailed {
return nil, base.LazyValue{}
}
if result == loadBlockOK {
if ikey, val := i.data.Last(); ikey != nil {
if i.blockLower != nil && i.cmp(ikey.UserKey, i.blockLower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
return ikey, val
}
// Else fall through to skipBackward.
} else {
// result == loadBlockIrrelevant. Enforce the lower bound here since
// don't want to bother moving to the previous block if lower bound is
// already exceeded. Note that the previous block starts with keys <=
// key.UserKey since even though this is the current block's
// separator, the same user key can span multiple blocks.
if i.lower != nil && i.cmp(ikey.UserKey, i.lower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
}
return i.skipBackward()
}
// Next implements internalIterator.Next, as documented in the pebble
// package.
// Note: compactionIterator.Next mirrors the implementation of Iterator.Next
// due to performance. Keep the two in sync.
func (i *singleLevelIterator) Next() (*InternalKey, base.LazyValue) {
if i.exhaustedBounds == +1 {
panic("Next called even though exhausted upper bound")
}
i.exhaustedBounds = 0
i.maybeFilteredKeysSingleLevel = false
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
if i.err != nil {
// TODO(jackson): Can this case be turned into a panic? Once an error is
// encountered, the iterator must be re-seeked.
return nil, base.LazyValue{}
}
if key, val := i.data.Next(); key != nil {
if i.blockUpper != nil {
cmp := i.cmp(key.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return key, val
}
return i.skipForward()
}
// NextPrefix implements (base.InternalIterator).NextPrefix.
func (i *singleLevelIterator) NextPrefix(succKey []byte) (*InternalKey, base.LazyValue) {
if i.exhaustedBounds == +1 {
panic("NextPrefix called even though exhausted upper bound")
}
i.exhaustedBounds = 0
i.maybeFilteredKeysSingleLevel = false
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
if i.err != nil {
// TODO(jackson): Can this case be turned into a panic? Once an error is
// encountered, the iterator must be re-seeked.
return nil, base.LazyValue{}
}
if key, val := i.data.NextPrefix(succKey); key != nil {
if i.blockUpper != nil {
cmp := i.cmp(key.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return key, val
}
// Did not find prefix in the existing data block. This is the slow-path
// where we effectively seek the iterator.
var ikey *InternalKey
// The key is likely to be in the next data block, so try one step.
if ikey, _ = i.index.Next(); ikey == nil {
// The target key is greater than any key in the index block.
// Invalidate the block iterator so that a subsequent call to Prev()
// will return the last key in the table.
i.data.invalidate()
return nil, base.LazyValue{}
}
if i.cmp(succKey, ikey.UserKey) > 0 {
// Not in the next data block, so seek the index.
if ikey, _ = i.index.SeekGE(succKey, base.SeekGEFlagsNone); ikey == nil {
// The target key is greater than any key in the index block.
// Invalidate the block iterator so that a subsequent call to Prev()
// will return the last key in the table.
i.data.invalidate()
return nil, base.LazyValue{}
}
}
result := i.loadBlock(+1)
if result == loadBlockFailed {
return nil, base.LazyValue{}
}
if result == loadBlockIrrelevant {
// Enforce the upper bound here since don't want to bother moving
// to the next block if upper bound is already exceeded. Note that
// the next block starts with keys >= ikey.UserKey since even
// though this is the block separator, the same user key can span
// multiple blocks. If upper is exclusive we use >= below, else we use
// >.
if i.upper != nil {
cmp := i.cmp(ikey.UserKey, i.upper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
} else if key, val := i.data.SeekGE(succKey, base.SeekGEFlagsNone); key != nil {
if i.blockUpper != nil {
cmp := i.cmp(key.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return i.maybeVerifyKey(key, val)
}
return i.skipForward()
}
// Prev implements internalIterator.Prev, as documented in the pebble
// package.
func (i *singleLevelIterator) Prev() (*InternalKey, base.LazyValue) {
if i.exhaustedBounds == -1 {
panic("Prev called even though exhausted lower bound")
}
i.exhaustedBounds = 0
i.maybeFilteredKeysSingleLevel = false
// Seek optimization only applies until iterator is first positioned after SetBounds.
i.boundsCmp = 0
if i.err != nil {
return nil, base.LazyValue{}
}
if key, val := i.data.Prev(); key != nil {
if i.blockLower != nil && i.cmp(key.UserKey, i.blockLower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
return key, val
}
return i.skipBackward()
}
func (i *singleLevelIterator) skipForward() (*InternalKey, base.LazyValue) {
for {
var key *InternalKey
if key, _ = i.index.Next(); key == nil {
i.data.invalidate()
break
}
result := i.loadBlock(+1)
if result != loadBlockOK {
if i.err != nil {
break
}
if result == loadBlockFailed {
// We checked that i.index was at a valid entry, so
// loadBlockFailed could not have happened due to to i.index
// being exhausted, and must be due to an error.
panic("loadBlock should not have failed with no error")
}
// result == loadBlockIrrelevant. Enforce the upper bound here
// since don't want to bother moving to the next block if upper
// bound is already exceeded. Note that the next block starts with
// keys >= key.UserKey since even though this is the block
// separator, the same user key can span multiple blocks. If upper
// is exclusive we use >= below, else we use >.
if i.upper != nil {
cmp := i.cmp(key.UserKey, i.upper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
continue
}
if key, val := i.data.First(); key != nil {
if i.blockUpper != nil {
cmp := i.cmp(key.UserKey, i.blockUpper)
if (!i.endKeyInclusive && cmp >= 0) || cmp > 0 {
i.exhaustedBounds = +1
return nil, base.LazyValue{}
}
}
return i.maybeVerifyKey(key, val)
}
}
return nil, base.LazyValue{}
}
func (i *singleLevelIterator) skipBackward() (*InternalKey, base.LazyValue) {
for {
var key *InternalKey
if key, _ = i.index.Prev(); key == nil {
i.data.invalidate()
break
}
result := i.loadBlock(-1)
if result != loadBlockOK {
if i.err != nil {
break
}
if result == loadBlockFailed {
// We checked that i.index was at a valid entry, so
// loadBlockFailed could not have happened due to to i.index
// being exhausted, and must be due to an error.
panic("loadBlock should not have failed with no error")
}
// result == loadBlockIrrelevant. Enforce the lower bound here
// since don't want to bother moving to the previous block if lower
// bound is already exceeded. Note that the previous block starts with
// keys <= key.UserKey since even though this is the current block's
// separator, the same user key can span multiple blocks.
if i.lower != nil && i.cmp(key.UserKey, i.lower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
continue
}
key, val := i.data.Last()
if key == nil {
return nil, base.LazyValue{}
}
if i.blockLower != nil && i.cmp(key.UserKey, i.blockLower) < 0 {
i.exhaustedBounds = -1
return nil, base.LazyValue{}
}
return i.maybeVerifyKey(key, val)
}
return nil, base.LazyValue{}
}
// Error implements internalIterator.Error, as documented in the pebble
// package.
func (i *singleLevelIterator) Error() error {
if err := i.data.Error(); err != nil {
return err
}
return i.err
}
// MaybeFilteredKeys may be called when an iterator is exhausted to indicate
// whether or not the last positioning method may have skipped any keys due to
// block-property filters.
func (i *singleLevelIterator) MaybeFilteredKeys() bool {
return i.maybeFilteredKeysSingleLevel
}
// SetCloseHook sets a function that will be called when the iterator is
// closed.
func (i *singleLevelIterator) SetCloseHook(fn func(i Iterator) error) {
i.closeHook = fn
}
func firstError(err0, err1 error) error {
if err0 != nil {
return err0
}
return err1
}
// Close implements internalIterator.Close, as documented in the pebble
// package.
func (i *singleLevelIterator) Close() error {
i.iterStats.close()
var err error
if i.closeHook != nil {
err = firstError(err, i.closeHook(i))
}
err = firstError(err, i.data.Close())
err = firstError(err, i.index.Close())
if i.dataRH != nil {
err = firstError(err, i.dataRH.Close())
i.dataRH = nil
}
err = firstError(err, i.err)
if i.bpfs != nil {
releaseBlockPropertiesFilterer(i.bpfs)
}
if i.vbReader != nil {
i.vbReader.close()
}
if i.vbRH != nil {
err = firstError(err, i.vbRH.Close())
i.vbRH = nil
}
*i = i.resetForReuse()
singleLevelIterPool.Put(i)
return err
}
func (i *singleLevelIterator) String() string {
if i.vState != nil {
return i.vState.fileNum.String()
}
return i.reader.fileNum.String()
}