ceremonyclient/pebble/sstable/block.go

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2024-01-03 07:31:42 +00:00
// Copyright 2018 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"
"encoding/binary"
"unsafe"
"github.com/cockroachdb/errors"
"github.com/cockroachdb/pebble/internal/base"
"github.com/cockroachdb/pebble/internal/invariants"
"github.com/cockroachdb/pebble/internal/keyspan"
"github.com/cockroachdb/pebble/internal/manual"
"github.com/cockroachdb/pebble/internal/rangedel"
"github.com/cockroachdb/pebble/internal/rangekey"
)
func uvarintLen(v uint32) int {
i := 0
for v >= 0x80 {
v >>= 7
i++
}
return i + 1
}
type blockWriter struct {
restartInterval int
nEntries int
nextRestart int
buf []byte
// For datablocks in TableFormatPebblev3, we steal the most significant bit
// in restarts for encoding setHasSameKeyPrefixSinceLastRestart. This leaves
// us with 31 bits, which is more than enough (no one needs > 2GB blocks).
// Typically, restarts occur every 16 keys, and by storing this bit with the
// restart, we can optimize for the case where a user wants to skip to the
// next prefix which happens to be in the same data block, but is > 16 keys
// away. We have seen production situations with 100+ versions per MVCC key
// (which share the same prefix). Additionally, for such writers, the prefix
// compression of the key, that shares the key with the preceding key, is
// limited to the prefix part of the preceding key -- this ensures that when
// doing NPrefix (see blockIter) we don't need to assemble the full key
// for each step since by limiting the length of the shared key we are
// ensuring that any of the keys with the same prefix can be used to
// assemble the full key when the prefix does change.
restarts []uint32
// Do not read curKey directly from outside blockWriter since it can have
// the InternalKeyKindSSTableInternalObsoleteBit set. Use getCurKey() or
// getCurUserKey() instead.
curKey []byte
// curValue excludes the optional prefix provided to
// storeWithOptionalValuePrefix.
curValue []byte
prevKey []byte
tmp [4]byte
// We don't know the state of the sets that were at the end of the previous
// block, so this is initially 0. It may be true for the second and later
// restarts in a block. Not having inter-block information is fine since we
// will optimize by stepping through restarts only within the same block.
// Note that the first restart is the first key in the block.
setHasSameKeyPrefixSinceLastRestart bool
}
func (w *blockWriter) clear() {
*w = blockWriter{
buf: w.buf[:0],
restarts: w.restarts[:0],
curKey: w.curKey[:0],
curValue: w.curValue[:0],
prevKey: w.prevKey[:0],
}
}
// MaximumBlockSize is an extremely generous maximum block size of 256MiB. We
// explicitly place this limit to reserve a few bits in the restart for
// internal use.
const MaximumBlockSize = 1 << 28
const setHasSameKeyPrefixRestartMask uint32 = 1 << 31
const restartMaskLittleEndianHighByteWithoutSetHasSamePrefix byte = 0b0111_1111
const restartMaskLittleEndianHighByteOnlySetHasSamePrefix byte = 0b1000_0000
func (w *blockWriter) getCurKey() InternalKey {
k := base.DecodeInternalKey(w.curKey)
k.Trailer = k.Trailer & trailerObsoleteMask
return k
}
func (w *blockWriter) getCurUserKey() []byte {
n := len(w.curKey) - base.InternalTrailerLen
if n < 0 {
panic(errors.AssertionFailedf("corrupt key in blockWriter buffer"))
}
return w.curKey[:n:n]
}
// If !addValuePrefix, the valuePrefix is ignored.
func (w *blockWriter) storeWithOptionalValuePrefix(
keySize int,
value []byte,
maxSharedKeyLen int,
addValuePrefix bool,
valuePrefix valuePrefix,
setHasSameKeyPrefix bool,
) {
shared := 0
if !setHasSameKeyPrefix {
w.setHasSameKeyPrefixSinceLastRestart = false
}
if w.nEntries == w.nextRestart {
w.nextRestart = w.nEntries + w.restartInterval
restart := uint32(len(w.buf))
if w.setHasSameKeyPrefixSinceLastRestart {
restart = restart | setHasSameKeyPrefixRestartMask
}
w.setHasSameKeyPrefixSinceLastRestart = true
w.restarts = append(w.restarts, restart)
} else {
// TODO(peter): Manually inlined version of base.SharedPrefixLen(). This
// is 3% faster on BenchmarkWriter on go1.16. Remove if future versions
// show this to not be a performance win. For now, functions that use of
// unsafe cannot be inlined.
n := maxSharedKeyLen
if n > len(w.prevKey) {
n = len(w.prevKey)
}
asUint64 := func(b []byte, i int) uint64 {
return binary.LittleEndian.Uint64(b[i:])
}
for shared < n-7 && asUint64(w.curKey, shared) == asUint64(w.prevKey, shared) {
shared += 8
}
for shared < n && w.curKey[shared] == w.prevKey[shared] {
shared++
}
}
lenValuePlusOptionalPrefix := len(value)
if addValuePrefix {
lenValuePlusOptionalPrefix++
}
needed := 3*binary.MaxVarintLen32 + len(w.curKey[shared:]) + lenValuePlusOptionalPrefix
n := len(w.buf)
if cap(w.buf) < n+needed {
newCap := 2 * cap(w.buf)
if newCap == 0 {
newCap = 1024
}
for newCap < n+needed {
newCap *= 2
}
newBuf := make([]byte, n, newCap)
copy(newBuf, w.buf)
w.buf = newBuf
}
w.buf = w.buf[:n+needed]
// TODO(peter): Manually inlined versions of binary.PutUvarint(). This is 15%
// faster on BenchmarkWriter on go1.13. Remove if go1.14 or future versions
// show this to not be a performance win.
{
x := uint32(shared)
for x >= 0x80 {
w.buf[n] = byte(x) | 0x80
x >>= 7
n++
}
w.buf[n] = byte(x)
n++
}
{
x := uint32(keySize - shared)
for x >= 0x80 {
w.buf[n] = byte(x) | 0x80
x >>= 7
n++
}
w.buf[n] = byte(x)
n++
}
{
x := uint32(lenValuePlusOptionalPrefix)
for x >= 0x80 {
w.buf[n] = byte(x) | 0x80
x >>= 7
n++
}
w.buf[n] = byte(x)
n++
}
n += copy(w.buf[n:], w.curKey[shared:])
if addValuePrefix {
w.buf[n : n+1][0] = byte(valuePrefix)
n++
}
n += copy(w.buf[n:], value)
w.buf = w.buf[:n]
w.curValue = w.buf[n-len(value):]
w.nEntries++
}
func (w *blockWriter) add(key InternalKey, value []byte) {
w.addWithOptionalValuePrefix(
key, false, value, len(key.UserKey), false, 0, false)
}
// Callers that always set addValuePrefix to false should use add() instead.
//
// isObsolete indicates whether this key-value pair is obsolete in this
// sstable (only applicable when writing data blocks) -- see the comment in
// table.go and the longer one in format.go. addValuePrefix adds a 1 byte
// prefix to the value, specified in valuePrefix -- this is used for data
// blocks in TableFormatPebblev3 onwards for SETs (see the comment in
// format.go, with more details in value_block.go). setHasSameKeyPrefix is
// also used in TableFormatPebblev3 onwards for SETs.
func (w *blockWriter) addWithOptionalValuePrefix(
key InternalKey,
isObsolete bool,
value []byte,
maxSharedKeyLen int,
addValuePrefix bool,
valuePrefix valuePrefix,
setHasSameKeyPrefix bool,
) {
w.curKey, w.prevKey = w.prevKey, w.curKey
size := key.Size()
if cap(w.curKey) < size {
w.curKey = make([]byte, 0, size*2)
}
w.curKey = w.curKey[:size]
if isObsolete {
key.Trailer = key.Trailer | trailerObsoleteBit
}
key.Encode(w.curKey)
w.storeWithOptionalValuePrefix(
size, value, maxSharedKeyLen, addValuePrefix, valuePrefix, setHasSameKeyPrefix)
}
func (w *blockWriter) finish() []byte {
// Write the restart points to the buffer.
if w.nEntries == 0 {
// Every block must have at least one restart point.
if cap(w.restarts) > 0 {
w.restarts = w.restarts[:1]
w.restarts[0] = 0
} else {
w.restarts = append(w.restarts, 0)
}
}
tmp4 := w.tmp[:4]
for _, x := range w.restarts {
binary.LittleEndian.PutUint32(tmp4, x)
w.buf = append(w.buf, tmp4...)
}
binary.LittleEndian.PutUint32(tmp4, uint32(len(w.restarts)))
w.buf = append(w.buf, tmp4...)
result := w.buf
// Reset the block state.
w.nEntries = 0
w.nextRestart = 0
w.buf = w.buf[:0]
w.restarts = w.restarts[:0]
return result
}
// emptyBlockSize holds the size of an empty block. Every block ends
// in a uint32 trailer encoding the number of restart points within the
// block.
const emptyBlockSize = 4
func (w *blockWriter) estimatedSize() int {
return len(w.buf) + 4*len(w.restarts) + emptyBlockSize
}
type blockEntry struct {
offset int32
keyStart int32
keyEnd int32
valStart int32
valSize int32
}
// blockIter is an iterator over a single block of data.
//
// A blockIter provides an additional guarantee around key stability when a
// block has a restart interval of 1 (i.e. when there is no prefix
// compression). Key stability refers to whether the InternalKey.UserKey bytes
// returned by a positioning call will remain stable after a subsequent
// positioning call. The normal case is that a positioning call will invalidate
// any previously returned InternalKey.UserKey. If a block has a restart
// interval of 1 (no prefix compression), blockIter guarantees that
// InternalKey.UserKey will point to the key as stored in the block itself
// which will remain valid until the blockIter is closed. The key stability
// guarantee is used by the range tombstone and range key code, which knows that
// the respective blocks are always encoded with a restart interval of 1. This
// per-block key stability guarantee is sufficient for range tombstones and
// range deletes as they are always encoded in a single block.
//
// A blockIter also provides a value stability guarantee for range deletions and
// range keys since there is only a single range deletion and range key block
// per sstable and the blockIter will not release the bytes for the block until
// it is closed.
//
// Note on why blockIter knows about lazyValueHandling:
//
// blockIter's positioning functions (that return a LazyValue), are too
// complex to inline even prior to lazyValueHandling. blockIter.Next and
// blockIter.First were by far the cheapest and had costs 195 and 180
// respectively, which exceeds the budget of 80. We initially tried to keep
// the lazyValueHandling logic out of blockIter by wrapping it with a
// lazyValueDataBlockIter. singleLevelIter and twoLevelIter would use this
// wrapped iter. The functions in lazyValueDataBlockIter were simple, in that
// they called the corresponding blockIter func and then decided whether the
// value was in fact in-place (so return immediately) or needed further
// handling. But these also turned out too costly for mid-stack inlining since
// simple calls like the following have a high cost that is barely under the
// budget of 80
//
// k, v := i.data.SeekGE(key, flags) // cost 74
// k, v := i.data.Next() // cost 72
//
// We have 2 options for minimizing performance regressions:
// - Include the lazyValueHandling logic in the already non-inlineable
// blockIter functions: Since most of the time is spent in data block iters,
// it is acceptable to take the small hit of unnecessary branching (which
// hopefully branch prediction will predict correctly) for other kinds of
// blocks.
// - Duplicate the logic of singleLevelIterator and twoLevelIterator for the
// v3 sstable and only use the aforementioned lazyValueDataBlockIter for a
// v3 sstable. We would want to manage these copies via code generation.
//
// We have picked the first option here.
type blockIter struct {
cmp Compare
// offset is the byte index that marks where the current key/value is
// encoded in the block.
offset int32
// nextOffset is the byte index where the next key/value is encoded in the
// block.
nextOffset int32
// A "restart point" in a block is a point where the full key is encoded,
// instead of just having a suffix of the key encoded. See readEntry() for
// how prefix compression of keys works. Keys in between two restart points
// only have a suffix encoded in the block. When restart interval is 1, no
// prefix compression of keys happens. This is the case with range tombstone
// blocks.
//
// All restart offsets are listed in increasing order in
// i.ptr[i.restarts:len(block)-4], while numRestarts is encoded in the last
// 4 bytes of the block as a uint32 (i.ptr[len(block)-4:]). i.restarts can
// therefore be seen as the point where data in the block ends, and a list
// of offsets of all restart points begins.
restarts int32
// Number of restart points in this block. Encoded at the end of the block
// as a uint32.
numRestarts int32
globalSeqNum uint64
ptr unsafe.Pointer
data []byte
// key contains the raw key the iterator is currently pointed at. This may
// point directly to data stored in the block (for a key which has no prefix
// compression), to fullKey (for a prefix compressed key), or to a slice of
// data stored in cachedBuf (during reverse iteration).
key []byte
// fullKey is a buffer used for key prefix decompression.
fullKey []byte
// val contains the value the iterator is currently pointed at. If non-nil,
// this points to a slice of the block data.
val []byte
// lazyValue is val turned into a LazyValue, whenever a positioning method
// returns a non-nil key-value pair.
lazyValue base.LazyValue
// ikey contains the decoded InternalKey the iterator is currently pointed
// at. Note that the memory backing ikey.UserKey is either data stored
// directly in the block, fullKey, or cachedBuf. The key stability guarantee
// for blocks built with a restart interval of 1 is achieved by having
// ikey.UserKey always point to data stored directly in the block.
ikey InternalKey
// cached and cachedBuf are used during reverse iteration. They are needed
// because we can't perform prefix decoding in reverse, only in the forward
// direction. In order to iterate in reverse, we decode and cache the entries
// between two restart points.
//
// Note that cached[len(cached)-1] contains the previous entry to the one the
// blockIter is currently pointed at. As usual, nextOffset will contain the
// offset of the next entry. During reverse iteration, nextOffset will be
// updated to point to offset, and we'll set the blockIter to point at the
// entry cached[len(cached)-1]. See Prev() for more details.
//
// For a block encoded with a restart interval of 1, cached and cachedBuf
// will not be used as there are no prefix compressed entries between the
// restart points.
cached []blockEntry
cachedBuf []byte
handle bufferHandle
// for block iteration for already loaded blocks.
firstUserKey []byte
lazyValueHandling struct {
vbr *valueBlockReader
hasValuePrefix bool
}
hideObsoletePoints bool
}
// blockIter implements the base.InternalIterator interface.
var _ base.InternalIterator = (*blockIter)(nil)
func newBlockIter(cmp Compare, block block) (*blockIter, error) {
i := &blockIter{}
return i, i.init(cmp, block, 0, false)
}
func (i *blockIter) String() string {
return "block"
}
func (i *blockIter) init(
cmp Compare, block block, globalSeqNum uint64, hideObsoletePoints bool,
) error {
numRestarts := int32(binary.LittleEndian.Uint32(block[len(block)-4:]))
if numRestarts == 0 {
return base.CorruptionErrorf("pebble/table: invalid table (block has no restart points)")
}
i.cmp = cmp
i.restarts = int32(len(block)) - 4*(1+numRestarts)
i.numRestarts = numRestarts
i.globalSeqNum = globalSeqNum
i.ptr = unsafe.Pointer(&block[0])
i.data = block
i.fullKey = i.fullKey[:0]
i.val = nil
i.hideObsoletePoints = hideObsoletePoints
i.clearCache()
if i.restarts > 0 {
if err := i.readFirstKey(); err != nil {
return err
}
} else {
// Block is empty.
i.firstUserKey = nil
}
return nil
}
// NB: two cases of hideObsoletePoints:
// - Local sstable iteration: globalSeqNum will be set iff the sstable was
// ingested.
// - Foreign sstable iteration: globalSeqNum is always set.
func (i *blockIter) initHandle(
cmp Compare, block bufferHandle, globalSeqNum uint64, hideObsoletePoints bool,
) error {
i.handle.Release()
i.handle = block
return i.init(cmp, block.Get(), globalSeqNum, hideObsoletePoints)
}
func (i *blockIter) invalidate() {
i.clearCache()
i.offset = 0
i.nextOffset = 0
i.restarts = 0
i.numRestarts = 0
i.data = nil
}
// isDataInvalidated returns true when the blockIter has been invalidated
// using an invalidate call. NB: this is different from blockIter.Valid
// which is part of the InternalIterator implementation.
func (i *blockIter) isDataInvalidated() bool {
return i.data == nil
}
func (i *blockIter) resetForReuse() blockIter {
return blockIter{
fullKey: i.fullKey[:0],
cached: i.cached[:0],
cachedBuf: i.cachedBuf[:0],
data: nil,
}
}
func (i *blockIter) readEntry() {
ptr := unsafe.Pointer(uintptr(i.ptr) + uintptr(i.offset))
// This is an ugly performance hack. Reading entries from blocks is one of
// the inner-most routines and decoding the 3 varints per-entry takes
// significant time. Neither go1.11 or go1.12 will inline decodeVarint for
// us, so we do it manually. This provides a 10-15% performance improvement
// on blockIter benchmarks on both go1.11 and go1.12.
//
// TODO(peter): remove this hack if go:inline is ever supported.
var shared uint32
if a := *((*uint8)(ptr)); a < 128 {
shared = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
shared = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
shared = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
shared = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
shared = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
var unshared uint32
if a := *((*uint8)(ptr)); a < 128 {
unshared = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
unshared = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
unshared = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
unshared = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
unshared = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
var value uint32
if a := *((*uint8)(ptr)); a < 128 {
value = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
value = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
value = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
value = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
value = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
unsharedKey := getBytes(ptr, int(unshared))
// TODO(sumeer): move this into the else block below.
i.fullKey = append(i.fullKey[:shared], unsharedKey...)
if shared == 0 {
// Provide stability for the key across positioning calls if the key
// doesn't share a prefix with the previous key. This removes requiring the
// key to be copied if the caller knows the block has a restart interval of
// 1. An important example of this is range-del blocks.
i.key = unsharedKey
} else {
i.key = i.fullKey
}
ptr = unsafe.Pointer(uintptr(ptr) + uintptr(unshared))
i.val = getBytes(ptr, int(value))
i.nextOffset = int32(uintptr(ptr)-uintptr(i.ptr)) + int32(value)
}
func (i *blockIter) readFirstKey() error {
ptr := i.ptr
// This is an ugly performance hack. Reading entries from blocks is one of
// the inner-most routines and decoding the 3 varints per-entry takes
// significant time. Neither go1.11 or go1.12 will inline decodeVarint for
// us, so we do it manually. This provides a 10-15% performance improvement
// on blockIter benchmarks on both go1.11 and go1.12.
//
// TODO(peter): remove this hack if go:inline is ever supported.
if shared := *((*uint8)(ptr)); shared == 0 {
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else {
// The shared length is != 0, which is invalid.
panic("first key in block must have zero shared length")
}
var unshared uint32
if a := *((*uint8)(ptr)); a < 128 {
unshared = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
unshared = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
unshared = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
unshared = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
unshared = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
// Skip the value length.
if a := *((*uint8)(ptr)); a < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a := *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); a < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if a := *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); a < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if a := *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); a < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
firstKey := getBytes(ptr, int(unshared))
// Manually inlining base.DecodeInternalKey provides a 5-10% speedup on
// BlockIter benchmarks.
if n := len(firstKey) - 8; n >= 0 {
i.firstUserKey = firstKey[:n:n]
} else {
i.firstUserKey = nil
return base.CorruptionErrorf("pebble/table: invalid firstKey in block")
}
return nil
}
// The sstable internal obsolete bit is set when writing a block and unset by
// blockIter, so no code outside block writing/reading code ever sees it.
const trailerObsoleteBit = uint64(base.InternalKeyKindSSTableInternalObsoleteBit)
const trailerObsoleteMask = (InternalKeySeqNumMax << 8) | uint64(base.InternalKeyKindSSTableInternalObsoleteMask)
func (i *blockIter) decodeInternalKey(key []byte) (hiddenPoint bool) {
// Manually inlining base.DecodeInternalKey provides a 5-10% speedup on
// BlockIter benchmarks.
if n := len(key) - 8; n >= 0 {
trailer := binary.LittleEndian.Uint64(key[n:])
hiddenPoint = i.hideObsoletePoints &&
(trailer&trailerObsoleteBit != 0)
i.ikey.Trailer = trailer & trailerObsoleteMask
i.ikey.UserKey = key[:n:n]
if i.globalSeqNum != 0 {
i.ikey.SetSeqNum(i.globalSeqNum)
}
} else {
i.ikey.Trailer = uint64(InternalKeyKindInvalid)
i.ikey.UserKey = nil
}
return hiddenPoint
}
func (i *blockIter) clearCache() {
i.cached = i.cached[:0]
i.cachedBuf = i.cachedBuf[:0]
}
func (i *blockIter) cacheEntry() {
var valStart int32
valSize := int32(len(i.val))
if valSize > 0 {
valStart = int32(uintptr(unsafe.Pointer(&i.val[0])) - uintptr(i.ptr))
}
i.cached = append(i.cached, blockEntry{
offset: i.offset,
keyStart: int32(len(i.cachedBuf)),
keyEnd: int32(len(i.cachedBuf) + len(i.key)),
valStart: valStart,
valSize: valSize,
})
i.cachedBuf = append(i.cachedBuf, i.key...)
}
func (i *blockIter) getFirstUserKey() []byte {
return i.firstUserKey
}
// SeekGE implements internalIterator.SeekGE, as documented in the pebble
// package.
func (i *blockIter) SeekGE(key []byte, flags base.SeekGEFlags) (*InternalKey, base.LazyValue) {
if invariants.Enabled && i.isDataInvalidated() {
panic(errors.AssertionFailedf("invalidated blockIter used"))
}
i.clearCache()
// Find the index of the smallest restart point whose key is > the key
// sought; index will be numRestarts if there is no such restart point.
i.offset = 0
var index int32
{
// NB: manually inlined sort.Seach is ~5% faster.
//
// Define f(-1) == false and f(n) == true.
// Invariant: f(index-1) == false, f(upper) == true.
upper := i.numRestarts
for index < upper {
h := int32(uint(index+upper) >> 1) // avoid overflow when computing h
// index ≤ h < upper
offset := decodeRestart(i.data[i.restarts+4*h:])
// For a restart point, there are 0 bytes shared with the previous key.
// The varint encoding of 0 occupies 1 byte.
ptr := unsafe.Pointer(uintptr(i.ptr) + uintptr(offset+1))
// Decode the key at that restart point, and compare it to the key
// sought. See the comment in readEntry for why we manually inline the
// varint decoding.
var v1 uint32
if a := *((*uint8)(ptr)); a < 128 {
v1 = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
v1 = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
v1 = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
v1 = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
v1 = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
if *((*uint8)(ptr)) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
// Manually inlining part of base.DecodeInternalKey provides a 5-10%
// speedup on BlockIter benchmarks.
s := getBytes(ptr, int(v1))
var k []byte
if n := len(s) - 8; n >= 0 {
k = s[:n:n]
}
// Else k is invalid, and left as nil
if i.cmp(key, k) > 0 {
// The search key is greater than the user key at this restart point.
// Search beyond this restart point, since we are trying to find the
// first restart point with a user key >= the search key.
index = h + 1 // preserves f(i-1) == false
} else {
// k >= search key, so prune everything after index (since index
// satisfies the property we are looking for).
upper = h // preserves f(j) == true
}
}
// index == upper, f(index-1) == false, and f(upper) (= f(index)) == true
// => answer is index.
}
// index is the first restart point with key >= search key. Define the keys
// between a restart point and the next restart point as belonging to that
// restart point.
//
// Since keys are strictly increasing, if index > 0 then the restart point
// at index-1 will be the first one that has some keys belonging to it that
// could be equal to the search key. If index == 0, then all keys in this
// block are larger than the key sought, and offset remains at zero.
if index > 0 {
i.offset = decodeRestart(i.data[i.restarts+4*(index-1):])
}
i.readEntry()
hiddenPoint := i.decodeInternalKey(i.key)
// Iterate from that restart point to somewhere >= the key sought.
if !i.valid() {
return nil, base.LazyValue{}
}
if !hiddenPoint && i.cmp(i.ikey.UserKey, key) >= 0 {
// Initialize i.lazyValue
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
for i.Next(); i.valid(); i.Next() {
if i.cmp(i.ikey.UserKey, key) >= 0 {
// i.Next() has already initialized i.lazyValue.
return &i.ikey, i.lazyValue
}
}
return nil, base.LazyValue{}
}
// SeekPrefixGE implements internalIterator.SeekPrefixGE, as documented in the
// pebble package.
func (i *blockIter) SeekPrefixGE(
prefix, key []byte, flags base.SeekGEFlags,
) (*base.InternalKey, base.LazyValue) {
// This should never be called as prefix iteration is handled by sstable.Iterator.
panic("pebble: SeekPrefixGE unimplemented")
}
// SeekLT implements internalIterator.SeekLT, as documented in the pebble
// package.
func (i *blockIter) SeekLT(key []byte, flags base.SeekLTFlags) (*InternalKey, base.LazyValue) {
if invariants.Enabled && i.isDataInvalidated() {
panic(errors.AssertionFailedf("invalidated blockIter used"))
}
i.clearCache()
// Find the index of the smallest restart point whose key is >= the key
// sought; index will be numRestarts if there is no such restart point.
i.offset = 0
var index int32
{
// NB: manually inlined sort.Search is ~5% faster.
//
// Define f(-1) == false and f(n) == true.
// Invariant: f(index-1) == false, f(upper) == true.
upper := i.numRestarts
for index < upper {
h := int32(uint(index+upper) >> 1) // avoid overflow when computing h
// index ≤ h < upper
offset := decodeRestart(i.data[i.restarts+4*h:])
// For a restart point, there are 0 bytes shared with the previous key.
// The varint encoding of 0 occupies 1 byte.
ptr := unsafe.Pointer(uintptr(i.ptr) + uintptr(offset+1))
// Decode the key at that restart point, and compare it to the key
// sought. See the comment in readEntry for why we manually inline the
// varint decoding.
var v1 uint32
if a := *((*uint8)(ptr)); a < 128 {
v1 = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
v1 = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
v1 = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
v1 = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
v1 = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
if *((*uint8)(ptr)) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))) < 128 {
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
// Manually inlining part of base.DecodeInternalKey provides a 5-10%
// speedup on BlockIter benchmarks.
s := getBytes(ptr, int(v1))
var k []byte
if n := len(s) - 8; n >= 0 {
k = s[:n:n]
}
// Else k is invalid, and left as nil
if i.cmp(key, k) > 0 {
// The search key is greater than the user key at this restart point.
// Search beyond this restart point, since we are trying to find the
// first restart point with a user key >= the search key.
index = h + 1 // preserves f(i-1) == false
} else {
// k >= search key, so prune everything after index (since index
// satisfies the property we are looking for).
upper = h // preserves f(j) == true
}
}
// index == upper, f(index-1) == false, and f(upper) (= f(index)) == true
// => answer is index.
}
// index is the first restart point with key >= search key. Define the keys
// between a restart point and the next restart point as belonging to that
// restart point. Note that index could be equal to i.numRestarts, i.e., we
// are past the last restart.
//
// Since keys are strictly increasing, if index > 0 then the restart point
// at index-1 will be the first one that has some keys belonging to it that
// are less than the search key. If index == 0, then all keys in this block
// are larger than the search key, so there is no match.
targetOffset := i.restarts
if index > 0 {
i.offset = decodeRestart(i.data[i.restarts+4*(index-1):])
if index < i.numRestarts {
targetOffset = decodeRestart(i.data[i.restarts+4*(index):])
}
} else if index == 0 {
// If index == 0 then all keys in this block are larger than the key
// sought.
i.offset = -1
i.nextOffset = 0
return nil, base.LazyValue{}
}
// Iterate from that restart point to somewhere >= the key sought, then back
// up to the previous entry. The expectation is that we'll be performing
// reverse iteration, so we cache the entries as we advance forward.
i.nextOffset = i.offset
for {
i.offset = i.nextOffset
i.readEntry()
// When hidden keys are common, there is additional optimization possible
// by not caching entries that are hidden (note that some calls to
// cacheEntry don't decode the internal key before caching, but checking
// whether a key is hidden does not require full decoding). However, we do
// need to use the blockEntry.offset in the cache for the first entry at
// the reset point to do the binary search when the cache is empty -- so
// we would need to cache that first entry (though not the key) even if
// was hidden. Our current assumption is that if there are large numbers
// of hidden keys we will be able to skip whole blocks (using block
// property filters) so we don't bother optimizing.
hiddenPoint := i.decodeInternalKey(i.key)
// NB: we don't use the hiddenPoint return value of decodeInternalKey
// since we want to stop as soon as we reach a key >= ikey.UserKey, so
// that we can reverse.
if i.cmp(i.ikey.UserKey, key) >= 0 {
// The current key is greater than or equal to our search key. Back up to
// the previous key which was less than our search key. Note that this for
// loop will execute at least once with this if-block not being true, so
// the key we are backing up to is the last one this loop cached.
return i.Prev()
}
if i.nextOffset >= targetOffset {
// We've reached the end of the current restart block. Return the
// current key if not hidden, else call Prev().
//
// When the restart interval is 1, the first iteration of the for loop
// will bring us here. In that case ikey is backed by the block so we
// get the desired key stability guarantee for the lifetime of the
// blockIter. That is, we never cache anything and therefore never
// return a key backed by cachedBuf.
if hiddenPoint {
return i.Prev()
}
break
}
i.cacheEntry()
}
if !i.valid() {
return nil, base.LazyValue{}
}
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
// First implements internalIterator.First, as documented in the pebble
// package.
func (i *blockIter) First() (*InternalKey, base.LazyValue) {
if invariants.Enabled && i.isDataInvalidated() {
panic(errors.AssertionFailedf("invalidated blockIter used"))
}
i.offset = 0
if !i.valid() {
return nil, base.LazyValue{}
}
i.clearCache()
i.readEntry()
hiddenPoint := i.decodeInternalKey(i.key)
if hiddenPoint {
return i.Next()
}
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
func decodeRestart(b []byte) int32 {
_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
return int32(uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 |
uint32(b[3]&restartMaskLittleEndianHighByteWithoutSetHasSamePrefix)<<24)
}
// Last implements internalIterator.Last, as documented in the pebble package.
func (i *blockIter) Last() (*InternalKey, base.LazyValue) {
if invariants.Enabled && i.isDataInvalidated() {
panic(errors.AssertionFailedf("invalidated blockIter used"))
}
// Seek forward from the last restart point.
i.offset = decodeRestart(i.data[i.restarts+4*(i.numRestarts-1):])
if !i.valid() {
return nil, base.LazyValue{}
}
i.readEntry()
i.clearCache()
for i.nextOffset < i.restarts {
i.cacheEntry()
i.offset = i.nextOffset
i.readEntry()
}
hiddenPoint := i.decodeInternalKey(i.key)
if hiddenPoint {
return i.Prev()
}
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
// Next implements internalIterator.Next, as documented in the pebble
// package.
func (i *blockIter) Next() (*InternalKey, base.LazyValue) {
if len(i.cachedBuf) > 0 {
// We're switching from reverse iteration to forward iteration. We need to
// populate i.fullKey with the current key we're positioned at so that
// readEntry() can use i.fullKey for key prefix decompression. Note that we
// don't know whether i.key is backed by i.cachedBuf or i.fullKey (if
// SeekLT was the previous call, i.key may be backed by i.fullKey), but
// copying into i.fullKey works for both cases.
//
// TODO(peter): Rather than clearing the cache, we could instead use the
// cache until it is exhausted. This would likely be faster than falling
// through to the normal forward iteration code below.
i.fullKey = append(i.fullKey[:0], i.key...)
i.clearCache()
}
start:
i.offset = i.nextOffset
if !i.valid() {
return nil, base.LazyValue{}
}
i.readEntry()
// Manually inlined version of i.decodeInternalKey(i.key).
if n := len(i.key) - 8; n >= 0 {
trailer := binary.LittleEndian.Uint64(i.key[n:])
hiddenPoint := i.hideObsoletePoints &&
(trailer&trailerObsoleteBit != 0)
i.ikey.Trailer = trailer & trailerObsoleteMask
i.ikey.UserKey = i.key[:n:n]
if i.globalSeqNum != 0 {
i.ikey.SetSeqNum(i.globalSeqNum)
}
if hiddenPoint {
goto start
}
} else {
i.ikey.Trailer = uint64(InternalKeyKindInvalid)
i.ikey.UserKey = nil
}
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
// NextPrefix implements (base.InternalIterator).NextPrefix.
func (i *blockIter) NextPrefix(succKey []byte) (*InternalKey, base.LazyValue) {
if i.lazyValueHandling.hasValuePrefix {
return i.nextPrefixV3(succKey)
}
const nextsBeforeSeek = 3
k, v := i.Next()
for j := 1; k != nil && i.cmp(k.UserKey, succKey) < 0; j++ {
if j >= nextsBeforeSeek {
return i.SeekGE(succKey, base.SeekGEFlagsNone)
}
k, v = i.Next()
}
return k, v
}
func (i *blockIter) nextPrefixV3(succKey []byte) (*InternalKey, base.LazyValue) {
// Doing nexts that involve a key comparison can be expensive (and the cost
// depends on the key length), so we use the same threshold of 3 that we use
// for TableFormatPebblev2 in blockIter.nextPrefix above. The next fast path
// that looks at setHasSamePrefix takes ~5ns per key, which is ~150x faster
// than doing a SeekGE within the block, so we do this 16 times
// (~5ns*16=80ns), and then switch to looking at restarts. Doing the binary
// search for the restart consumes > 100ns. If the number of versions is >
// 17, we will increment nextFastCount to 17, then do a binary search, and
// on average need to find a key between two restarts, so another 8 steps
// corresponding to nextFastCount, for a mean total of 17 + 8 = 25 such
// steps.
//
// TODO(sumeer): use the configured restartInterval for the sstable when it
// was written (which we don't currently store) instead of the default value
// of 16.
const nextCmpThresholdBeforeSeek = 3
const nextFastThresholdBeforeRestarts = 16
nextCmpCount := 0
nextFastCount := 0
usedRestarts := false
// INVARIANT: blockIter is valid.
if invariants.Enabled && !i.valid() {
panic(errors.AssertionFailedf("nextPrefixV3 called on invalid blockIter"))
}
prevKeyIsSet := i.ikey.Kind() == InternalKeyKindSet
for {
i.offset = i.nextOffset
if !i.valid() {
return nil, base.LazyValue{}
}
// Need to decode the length integers, so we can compute nextOffset.
ptr := unsafe.Pointer(uintptr(i.ptr) + uintptr(i.offset))
// This is an ugly performance hack. Reading entries from blocks is one of
// the inner-most routines and decoding the 3 varints per-entry takes
// significant time. Neither go1.11 or go1.12 will inline decodeVarint for
// us, so we do it manually. This provides a 10-15% performance improvement
// on blockIter benchmarks on both go1.11 and go1.12.
//
// TODO(peter): remove this hack if go:inline is ever supported.
// Decode the shared key length integer.
var shared uint32
if a := *((*uint8)(ptr)); a < 128 {
shared = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
shared = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
shared = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
shared = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
shared = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
// Decode the unshared key length integer.
var unshared uint32
if a := *((*uint8)(ptr)); a < 128 {
unshared = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
unshared = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
unshared = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
unshared = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
unshared = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
// Decode the value length integer.
var value uint32
if a := *((*uint8)(ptr)); a < 128 {
value = uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 1)
} else if a, b := a&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 1))); b < 128 {
value = uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 2)
} else if b, c := b&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 2))); c < 128 {
value = uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 3)
} else if c, d := c&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 3))); d < 128 {
value = uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 4)
} else {
d, e := d&0x7f, *((*uint8)(unsafe.Pointer(uintptr(ptr) + 4)))
value = uint32(e)<<28 | uint32(d)<<21 | uint32(c)<<14 | uint32(b)<<7 | uint32(a)
ptr = unsafe.Pointer(uintptr(ptr) + 5)
}
// The starting position of the value.
valuePtr := unsafe.Pointer(uintptr(ptr) + uintptr(unshared))
i.nextOffset = int32(uintptr(valuePtr)-uintptr(i.ptr)) + int32(value)
if invariants.Enabled && unshared < 8 {
// This should not happen since only the key prefix is shared, so even
// if the prefix length is the same as the user key length, the unshared
// will include the trailer.
panic(errors.AssertionFailedf("unshared %d is too small", unshared))
}
// The trailer is written in little endian, so the key kind is the first
// byte in the trailer that is encoded in the slice [unshared-8:unshared].
keyKind := InternalKeyKind((*[manual.MaxArrayLen]byte)(ptr)[unshared-8])
keyKind = keyKind & base.InternalKeyKindSSTableInternalObsoleteMask
prefixChanged := false
if keyKind == InternalKeyKindSet {
if invariants.Enabled && value == 0 {
panic(errors.AssertionFailedf("value is of length 0, but we expect a valuePrefix"))
}
valPrefix := *((*valuePrefix)(valuePtr))
if setHasSamePrefix(valPrefix) {
// Fast-path. No need to assemble i.fullKey, or update i.key. We know
// that subsequent keys will not have a shared length that is greater
// than the prefix of the current key, which is also the prefix of
// i.key. Since we are continuing to iterate, we don't need to
// initialize i.ikey and i.lazyValue (these are initialized before
// returning).
nextFastCount++
if nextFastCount > nextFastThresholdBeforeRestarts {
if usedRestarts {
// Exhausted iteration budget. This will never happen unless
// someone is using a restart interval > 16. It is just to guard
// against long restart intervals causing too much iteration.
break
}
// Haven't used restarts yet, so find the first restart at or beyond
// the current offset.
targetOffset := i.offset
var index int32
{
// NB: manually inlined sort.Sort is ~5% faster.
//
// f defined for a restart point is true iff the offset >=
// targetOffset.
// Define f(-1) == false and f(i.numRestarts) == true.
// Invariant: f(index-1) == false, f(upper) == true.
upper := i.numRestarts
for index < upper {
h := int32(uint(index+upper) >> 1) // avoid overflow when computing h
// index ≤ h < upper
offset := decodeRestart(i.data[i.restarts+4*h:])
if offset < targetOffset {
index = h + 1 // preserves f(index-1) == false
} else {
upper = h // preserves f(upper) == true
}
}
// index == upper, f(index-1) == false, and f(upper) (= f(index)) == true
// => answer is index.
}
usedRestarts = true
nextFastCount = 0
if index == i.numRestarts {
// Already past the last real restart, so iterate a bit more until
// we are done with the block.
continue
}
// Have some real restarts after index. NB: index is the first
// restart at or beyond the current offset.
startingIndex := index
for index != i.numRestarts &&
// The restart at index is 4 bytes written in little endian format
// starting at i.restart+4*index. The 0th byte is the least
// significant and the 3rd byte is the most significant. Since the
// most significant bit of the 3rd byte is what we use for
// encoding the set-has-same-prefix information, the indexing
// below has +3.
i.data[i.restarts+4*index+3]&restartMaskLittleEndianHighByteOnlySetHasSamePrefix != 0 {
// We still have the same prefix, so move to the next restart.
index++
}
// index is the first restart that did not have the same prefix.
if index != startingIndex {
// Managed to skip past at least one restart. Resume iteration
// from index-1. Since nextFastCount has been reset to 0, we
// should be able to iterate to the next prefix.
i.offset = decodeRestart(i.data[i.restarts+4*(index-1):])
i.readEntry()
}
// Else, unable to skip past any restart. Resume iteration. Since
// nextFastCount has been reset to 0, we should be able to iterate
// to the next prefix.
continue
}
continue
} else if prevKeyIsSet {
prefixChanged = true
}
} else {
prevKeyIsSet = false
}
// Slow-path cases:
// - (Likely) The prefix has changed.
// - (Unlikely) The prefix has not changed.
// We assemble the key etc. under the assumption that it is the likely
// case.
unsharedKey := getBytes(ptr, int(unshared))
// TODO(sumeer): move this into the else block below. This is a bit tricky
// since the current logic assumes we have always copied the latest key
// into fullKey, which is why when we get to the next key we can (a)
// access i.fullKey[:shared], (b) append only the unsharedKey to
// i.fullKey. For (a), we can access i.key[:shared] since that memory is
// valid (even if unshared). For (b), we will need to remember whether
// i.key refers to i.fullKey or not, and can append the unsharedKey only
// in the former case and for the latter case need to copy the shared part
// too. This same comment applies to the other place where we can do this
// optimization, in readEntry().
i.fullKey = append(i.fullKey[:shared], unsharedKey...)
i.val = getBytes(valuePtr, int(value))
if shared == 0 {
// Provide stability for the key across positioning calls if the key
// doesn't share a prefix with the previous key. This removes requiring the
// key to be copied if the caller knows the block has a restart interval of
// 1. An important example of this is range-del blocks.
i.key = unsharedKey
} else {
i.key = i.fullKey
}
// Manually inlined version of i.decodeInternalKey(i.key).
hiddenPoint := false
if n := len(i.key) - 8; n >= 0 {
trailer := binary.LittleEndian.Uint64(i.key[n:])
hiddenPoint = i.hideObsoletePoints &&
(trailer&trailerObsoleteBit != 0)
i.ikey.Trailer = trailer & trailerObsoleteMask
i.ikey.UserKey = i.key[:n:n]
if i.globalSeqNum != 0 {
i.ikey.SetSeqNum(i.globalSeqNum)
}
} else {
i.ikey.Trailer = uint64(InternalKeyKindInvalid)
i.ikey.UserKey = nil
}
nextCmpCount++
if invariants.Enabled && prefixChanged && i.cmp(i.ikey.UserKey, succKey) < 0 {
panic(errors.AssertionFailedf("prefix should have changed but %x < %x",
i.ikey.UserKey, succKey))
}
if prefixChanged || i.cmp(i.ikey.UserKey, succKey) >= 0 {
// Prefix has changed.
if hiddenPoint {
return i.Next()
}
if invariants.Enabled && !i.lazyValueHandling.hasValuePrefix {
panic(errors.AssertionFailedf("nextPrefixV3 being run for non-v3 sstable"))
}
if base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
// Else prefix has not changed.
if nextCmpCount >= nextCmpThresholdBeforeSeek {
break
}
}
return i.SeekGE(succKey, base.SeekGEFlagsNone)
}
// Prev implements internalIterator.Prev, as documented in the pebble
// package.
func (i *blockIter) Prev() (*InternalKey, base.LazyValue) {
start:
for n := len(i.cached) - 1; n >= 0; n-- {
i.nextOffset = i.offset
e := &i.cached[n]
i.offset = e.offset
i.val = getBytes(unsafe.Pointer(uintptr(i.ptr)+uintptr(e.valStart)), int(e.valSize))
// Manually inlined version of i.decodeInternalKey(i.key).
i.key = i.cachedBuf[e.keyStart:e.keyEnd]
if n := len(i.key) - 8; n >= 0 {
trailer := binary.LittleEndian.Uint64(i.key[n:])
hiddenPoint := i.hideObsoletePoints &&
(trailer&trailerObsoleteBit != 0)
if hiddenPoint {
continue
}
i.ikey.Trailer = trailer & trailerObsoleteMask
i.ikey.UserKey = i.key[:n:n]
if i.globalSeqNum != 0 {
i.ikey.SetSeqNum(i.globalSeqNum)
}
} else {
i.ikey.Trailer = uint64(InternalKeyKindInvalid)
i.ikey.UserKey = nil
}
i.cached = i.cached[:n]
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
i.clearCache()
if i.offset <= 0 {
i.offset = -1
i.nextOffset = 0
return nil, base.LazyValue{}
}
targetOffset := i.offset
var index int32
{
// NB: manually inlined sort.Sort is ~5% faster.
//
// Define f(-1) == false and f(n) == true.
// Invariant: f(index-1) == false, f(upper) == true.
upper := i.numRestarts
for index < upper {
h := int32(uint(index+upper) >> 1) // avoid overflow when computing h
// index ≤ h < upper
offset := decodeRestart(i.data[i.restarts+4*h:])
if offset < targetOffset {
// Looking for the first restart that has offset >= targetOffset, so
// ignore h and earlier.
index = h + 1 // preserves f(i-1) == false
} else {
upper = h // preserves f(j) == true
}
}
// index == upper, f(index-1) == false, and f(upper) (= f(index)) == true
// => answer is index.
}
// index is first restart with offset >= targetOffset. Note that
// targetOffset may not be at a restart point since one can call Prev()
// after Next() (so the cache was not populated) and targetOffset refers to
// the current entry. index-1 must have an offset < targetOffset (it can't
// be equal to targetOffset since the binary search would have selected that
// as the index).
i.offset = 0
if index > 0 {
i.offset = decodeRestart(i.data[i.restarts+4*(index-1):])
}
// TODO(sumeer): why is the else case not an error given targetOffset is a
// valid offset.
i.readEntry()
// We stop when i.nextOffset == targetOffset since the targetOffset is the
// entry we are stepping back from, and we don't need to cache the entry
// before it, since it is the candidate to return.
for i.nextOffset < targetOffset {
i.cacheEntry()
i.offset = i.nextOffset
i.readEntry()
}
hiddenPoint := i.decodeInternalKey(i.key)
if hiddenPoint {
// Use the cache.
goto start
}
if !i.lazyValueHandling.hasValuePrefix ||
base.TrailerKind(i.ikey.Trailer) != InternalKeyKindSet {
i.lazyValue = base.MakeInPlaceValue(i.val)
} else if i.lazyValueHandling.vbr == nil || !isValueHandle(valuePrefix(i.val[0])) {
i.lazyValue = base.MakeInPlaceValue(i.val[1:])
} else {
i.lazyValue = i.lazyValueHandling.vbr.getLazyValueForPrefixAndValueHandle(i.val)
}
return &i.ikey, i.lazyValue
}
// Key implements internalIterator.Key, as documented in the pebble package.
func (i *blockIter) Key() *InternalKey {
return &i.ikey
}
func (i *blockIter) value() base.LazyValue {
return i.lazyValue
}
// Error implements internalIterator.Error, as documented in the pebble
// package.
func (i *blockIter) Error() error {
return nil // infallible
}
// Close implements internalIterator.Close, as documented in the pebble
// package.
func (i *blockIter) Close() error {
i.handle.Release()
i.handle = bufferHandle{}
i.val = nil
i.lazyValue = base.LazyValue{}
i.lazyValueHandling.vbr = nil
return nil
}
func (i *blockIter) SetBounds(lower, upper []byte) {
// This should never be called as bounds are handled by sstable.Iterator.
panic("pebble: SetBounds unimplemented")
}
func (i *blockIter) SetContext(_ context.Context) {}
func (i *blockIter) valid() bool {
return i.offset >= 0 && i.offset < i.restarts
}
// fragmentBlockIter wraps a blockIter, implementing the
// keyspan.FragmentIterator interface. It's used for reading range deletion and
// range key blocks.
//
// Range deletions and range keys are fragmented before they're persisted to the
// block. Overlapping fragments have identical bounds. The fragmentBlockIter
// gathers all the fragments with identical bounds within a block and returns a
// single keyspan.Span describing all the keys defined over the span.
//
// # Memory lifetime
//
// A Span returned by fragmentBlockIter is only guaranteed to be stable until
// the next fragmentBlockIter iteration positioning method. A Span's Keys slice
// may be reused, so the user must not assume it's stable.
//
// Blocks holding range deletions and range keys are configured to use a restart
// interval of 1. This provides key stability. The caller may treat the various
// byte slices (start, end, suffix, value) as stable for the lifetime of the
// iterator.
type fragmentBlockIter struct {
blockIter blockIter
keyBuf [2]keyspan.Key
span keyspan.Span
err error
dir int8
closeHook func(i keyspan.FragmentIterator) error
// elideSameSeqnum, if true, returns only the first-occurring (in forward
// order) Key for each sequence number.
elideSameSeqnum bool
}
func (i *fragmentBlockIter) resetForReuse() fragmentBlockIter {
return fragmentBlockIter{blockIter: i.blockIter.resetForReuse()}
}
func (i *fragmentBlockIter) decodeSpanKeys(k *InternalKey, internalValue []byte) {
// TODO(jackson): The use of i.span.Keys to accumulate keys across multiple
// calls to Decode is too confusing and subtle. Refactor to make it
// explicit.
// decode the contents of the fragment's value. This always includes at
// least the end key: RANGEDELs store the end key directly as the value,
// whereas the various range key kinds store are more complicated. The
// details of the range key internal value format are documented within the
// internal/rangekey package.
switch k.Kind() {
case base.InternalKeyKindRangeDelete:
i.span = rangedel.Decode(*k, internalValue, i.span.Keys)
i.err = nil
case base.InternalKeyKindRangeKeySet, base.InternalKeyKindRangeKeyUnset, base.InternalKeyKindRangeKeyDelete:
i.span, i.err = rangekey.Decode(*k, internalValue, i.span.Keys)
default:
i.span = keyspan.Span{}
i.err = base.CorruptionErrorf("pebble: corrupt keyspan fragment of kind %d", k.Kind())
}
}
func (i *fragmentBlockIter) elideKeysOfSameSeqNum() {
if invariants.Enabled {
if !i.elideSameSeqnum || len(i.span.Keys) == 0 {
panic("elideKeysOfSameSeqNum called when it should not be")
}
}
lastSeqNum := i.span.Keys[0].SeqNum()
k := 1
for j := 1; j < len(i.span.Keys); j++ {
if lastSeqNum != i.span.Keys[j].SeqNum() {
lastSeqNum = i.span.Keys[j].SeqNum()
i.span.Keys[k] = i.span.Keys[j]
k++
}
}
i.span.Keys = i.span.Keys[:k]
}
// gatherForward gathers internal keys with identical bounds. Keys defined over
// spans of the keyspace are fragmented such that any overlapping key spans have
// identical bounds. When these spans are persisted to a range deletion or range
// key block, they may be persisted as multiple internal keys in order to encode
// multiple sequence numbers or key kinds.
//
// gatherForward iterates forward, re-combining the fragmented internal keys to
// reconstruct a keyspan.Span that holds all the keys defined over the span.
func (i *fragmentBlockIter) gatherForward(k *InternalKey, lazyValue base.LazyValue) *keyspan.Span {
i.span = keyspan.Span{}
if k == nil || !i.blockIter.valid() {
return nil
}
i.err = nil
// Use the i.keyBuf array to back the Keys slice to prevent an allocation
// when a span contains few keys.
i.span.Keys = i.keyBuf[:0]
// Decode the span's end key and individual keys from the value.
internalValue := lazyValue.InPlaceValue()
i.decodeSpanKeys(k, internalValue)
if i.err != nil {
return nil
}
prevEnd := i.span.End
// There might exist additional internal keys with identical bounds encoded
// within the block. Iterate forward, accumulating all the keys with
// identical bounds to s.
k, lazyValue = i.blockIter.Next()
internalValue = lazyValue.InPlaceValue()
for k != nil && i.blockIter.cmp(k.UserKey, i.span.Start) == 0 {
i.decodeSpanKeys(k, internalValue)
if i.err != nil {
return nil
}
// Since k indicates an equal start key, the encoded end key must
// exactly equal the original end key from the first internal key.
// Overlapping fragments are required to have exactly equal start and
// end bounds.
if i.blockIter.cmp(prevEnd, i.span.End) != 0 {
i.err = base.CorruptionErrorf("pebble: corrupt keyspan fragmentation")
i.span = keyspan.Span{}
return nil
}
k, lazyValue = i.blockIter.Next()
internalValue = lazyValue.InPlaceValue()
}
if i.elideSameSeqnum && len(i.span.Keys) > 0 {
i.elideKeysOfSameSeqNum()
}
// i.blockIter is positioned over the first internal key for the next span.
return &i.span
}
// gatherBackward gathers internal keys with identical bounds. Keys defined over
// spans of the keyspace are fragmented such that any overlapping key spans have
// identical bounds. When these spans are persisted to a range deletion or range
// key block, they may be persisted as multiple internal keys in order to encode
// multiple sequence numbers or key kinds.
//
// gatherBackward iterates backwards, re-combining the fragmented internal keys
// to reconstruct a keyspan.Span that holds all the keys defined over the span.
func (i *fragmentBlockIter) gatherBackward(k *InternalKey, lazyValue base.LazyValue) *keyspan.Span {
i.span = keyspan.Span{}
if k == nil || !i.blockIter.valid() {
return nil
}
i.err = nil
// Use the i.keyBuf array to back the Keys slice to prevent an allocation
// when a span contains few keys.
i.span.Keys = i.keyBuf[:0]
// Decode the span's end key and individual keys from the value.
internalValue := lazyValue.InPlaceValue()
i.decodeSpanKeys(k, internalValue)
if i.err != nil {
return nil
}
prevEnd := i.span.End
// There might exist additional internal keys with identical bounds encoded
// within the block. Iterate backward, accumulating all the keys with
// identical bounds to s.
k, lazyValue = i.blockIter.Prev()
internalValue = lazyValue.InPlaceValue()
for k != nil && i.blockIter.cmp(k.UserKey, i.span.Start) == 0 {
i.decodeSpanKeys(k, internalValue)
if i.err != nil {
return nil
}
// Since k indicates an equal start key, the encoded end key must
// exactly equal the original end key from the first internal key.
// Overlapping fragments are required to have exactly equal start and
// end bounds.
if i.blockIter.cmp(prevEnd, i.span.End) != 0 {
i.err = base.CorruptionErrorf("pebble: corrupt keyspan fragmentation")
i.span = keyspan.Span{}
return nil
}
k, lazyValue = i.blockIter.Prev()
internalValue = lazyValue.InPlaceValue()
}
// i.blockIter is positioned over the last internal key for the previous
// span.
// Backwards iteration encounters internal keys in the wrong order.
keyspan.SortKeysByTrailer(&i.span.Keys)
if i.elideSameSeqnum && len(i.span.Keys) > 0 {
i.elideKeysOfSameSeqNum()
}
return &i.span
}
// Error implements (keyspan.FragmentIterator).Error.
func (i *fragmentBlockIter) Error() error {
return i.err
}
// Close implements (keyspan.FragmentIterator).Close.
func (i *fragmentBlockIter) Close() error {
var err error
if i.closeHook != nil {
err = i.closeHook(i)
}
err = firstError(err, i.blockIter.Close())
return err
}
// First implements (keyspan.FragmentIterator).First
func (i *fragmentBlockIter) First() *keyspan.Span {
i.dir = +1
return i.gatherForward(i.blockIter.First())
}
// Last implements (keyspan.FragmentIterator).Last.
func (i *fragmentBlockIter) Last() *keyspan.Span {
i.dir = -1
return i.gatherBackward(i.blockIter.Last())
}
// Next implements (keyspan.FragmentIterator).Next.
func (i *fragmentBlockIter) Next() *keyspan.Span {
switch {
case i.dir == -1 && !i.span.Valid():
// Switching directions.
//
// i.blockIter is exhausted, before the first key. Move onto the first.
i.blockIter.First()
i.dir = +1
case i.dir == -1 && i.span.Valid():
// Switching directions.
//
// i.blockIter is currently positioned over the last internal key for
// the previous span. Next it once to move to the first internal key
// that makes up the current span, and gatherForwaad to land on the
// first internal key making up the next span.
//
// In the diagram below, if the last span returned to the user during
// reverse iteration was [b,c), i.blockIter is currently positioned at
// [a,b). The block iter must be positioned over [d,e) to gather the
// next span's fragments.
//
// ... [a,b) [b,c) [b,c) [b,c) [d,e) ...
// ^ ^
// i.blockIter want
if x := i.gatherForward(i.blockIter.Next()); invariants.Enabled && !x.Valid() {
panic("pebble: invariant violation: next entry unexpectedly invalid")
}
i.dir = +1
}
// We know that this blockIter has in-place values.
return i.gatherForward(&i.blockIter.ikey, base.MakeInPlaceValue(i.blockIter.val))
}
// Prev implements (keyspan.FragmentIterator).Prev.
func (i *fragmentBlockIter) Prev() *keyspan.Span {
switch {
case i.dir == +1 && !i.span.Valid():
// Switching directions.
//
// i.blockIter is exhausted, after the last key. Move onto the last.
i.blockIter.Last()
i.dir = -1
case i.dir == +1 && i.span.Valid():
// Switching directions.
//
// i.blockIter is currently positioned over the first internal key for
// the next span. Prev it once to move to the last internal key that
// makes up the current span, and gatherBackward to land on the last
// internal key making up the previous span.
//
// In the diagram below, if the last span returned to the user during
// forward iteration was [b,c), i.blockIter is currently positioned at
// [d,e). The block iter must be positioned over [a,b) to gather the
// previous span's fragments.
//
// ... [a,b) [b,c) [b,c) [b,c) [d,e) ...
// ^ ^
// want i.blockIter
if x := i.gatherBackward(i.blockIter.Prev()); invariants.Enabled && !x.Valid() {
panic("pebble: invariant violation: previous entry unexpectedly invalid")
}
i.dir = -1
}
// We know that this blockIter has in-place values.
return i.gatherBackward(&i.blockIter.ikey, base.MakeInPlaceValue(i.blockIter.val))
}
// SeekGE implements (keyspan.FragmentIterator).SeekGE.
func (i *fragmentBlockIter) SeekGE(k []byte) *keyspan.Span {
if s := i.SeekLT(k); s != nil && i.blockIter.cmp(k, s.End) < 0 {
return s
}
// TODO(jackson): If the above i.SeekLT(k) discovers a span but the span
// doesn't meet the k < s.End comparison, then there's no need for the
// SeekLT to gatherBackward.
return i.Next()
}
// SeekLT implements (keyspan.FragmentIterator).SeekLT.
func (i *fragmentBlockIter) SeekLT(k []byte) *keyspan.Span {
i.dir = -1
return i.gatherBackward(i.blockIter.SeekLT(k, base.SeekLTFlagsNone))
}
// String implements fmt.Stringer.
func (i *fragmentBlockIter) String() string {
return "fragment-block-iter"
}
// SetCloseHook implements sstable.FragmentIterator.
func (i *fragmentBlockIter) SetCloseHook(fn func(i keyspan.FragmentIterator) error) {
i.closeHook = fn
}