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sstable/rowblk: extract block-level suffix rewriting
Move the suffix-rewriting logic that's specific to row-based blocks into a rowblk.Rewriter type. In future work, a columnar equivalent will be introduced.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,94 @@ | ||
| // Copyright 2024 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 rowblk | ||
|
|
||
| import ( | ||
| "bytes" | ||
|
|
||
| "github.com/cockroachdb/errors" | ||
| "github.com/cockroachdb/pebble/internal/base" | ||
| "github.com/cockroachdb/pebble/internal/bytealloc" | ||
| "github.com/cockroachdb/pebble/sstable/block" | ||
| ) | ||
|
|
||
| // NewRewriter constructs a new rewriter. | ||
| func NewRewriter(comparer *base.Comparer, restartInterval int) *Rewriter { | ||
| rw := &Rewriter{comparer: comparer} | ||
| rw.writer.RestartInterval = restartInterval | ||
| return rw | ||
| } | ||
|
|
||
| // Rewriter may be used to rewrite row-based blocks. | ||
| type Rewriter struct { | ||
| comparer *base.Comparer | ||
| // bufs resued each call to Rewrite. | ||
| writer Writer | ||
| iter Iter | ||
| scratchKey base.InternalKey | ||
| // alloc grown throughout the lifetime of the rewriter. | ||
| keyAlloc bytealloc.A | ||
| } | ||
|
|
||
| // RewriteSuffixes rewrites the input block. It expects the input block to only | ||
| // contain keys with the suffix `from`. It rewrites the block to contain the | ||
| // same keys with the suffix `to`. | ||
| // | ||
| // RewriteSuffixes returns the start and end keys of the rewritten block, and the | ||
| // finished rewritten block. | ||
| func (r *Rewriter) RewriteSuffixes( | ||
| input []byte, from []byte, to []byte, | ||
| ) (start, end base.InternalKey, rewritten []byte, err error) { | ||
| if err := r.iter.Init(r.comparer.Compare, r.comparer.Split, input, block.NoTransforms); err != nil { | ||
| return base.InternalKey{}, base.InternalKey{}, nil, err | ||
| } | ||
| if cap(r.writer.restarts) < int(r.iter.restarts) { | ||
| r.writer.restarts = make([]uint32, 0, r.iter.restarts) | ||
| } | ||
| if cap(r.writer.buf) == 0 { | ||
| r.writer.buf = make([]byte, 0, len(input)) | ||
| } | ||
| if cap(r.writer.restarts) < int(r.iter.numRestarts) { | ||
| r.writer.restarts = make([]uint32, 0, r.iter.numRestarts) | ||
| } | ||
| for kv := r.iter.First(); kv != nil; kv = r.iter.Next() { | ||
| if kv.Kind() != base.InternalKeyKindSet { | ||
| return base.InternalKey{}, base.InternalKey{}, nil, | ||
| errors.New("key does not have expected kind (set)") | ||
| } | ||
| si := r.comparer.Split(kv.K.UserKey) | ||
| oldSuffix := kv.K.UserKey[si:] | ||
| if !bytes.Equal(oldSuffix, from) { | ||
| return base.InternalKey{}, base.InternalKey{}, nil, | ||
| errors.Errorf("key has suffix %q, expected %q", oldSuffix, from) | ||
| } | ||
| newLen := si + len(to) | ||
| if cap(r.scratchKey.UserKey) < newLen { | ||
| r.scratchKey.UserKey = make([]byte, 0, len(kv.K.UserKey)*2+len(to)-len(from)) | ||
| } | ||
|
|
||
| r.scratchKey.Trailer = kv.K.Trailer | ||
| r.scratchKey.UserKey = r.scratchKey.UserKey[:newLen] | ||
| copy(r.scratchKey.UserKey, kv.K.UserKey[:si]) | ||
| copy(r.scratchKey.UserKey[si:], to) | ||
|
|
||
| // NB: for TableFormatPebblev3 and higher, since | ||
| // !iter.lazyValueHandling.hasValuePrefix, it will return the raw value | ||
| // in the block, which includes the 1-byte prefix. This is fine since bw | ||
| // also does not know about the prefix and will preserve it in bw.add. | ||
| v := kv.InPlaceValue() | ||
| r.writer.Add(r.scratchKey, v) | ||
| if start.UserKey == nil { | ||
| // Copy the first key. | ||
| start.Trailer = r.scratchKey.Trailer | ||
| r.keyAlloc, start.UserKey = r.keyAlloc.Copy(r.scratchKey.UserKey) | ||
| } | ||
| } | ||
| // Copy the last key. | ||
| end.Trailer = r.scratchKey.Trailer | ||
| r.keyAlloc, end.UserKey = r.keyAlloc.Copy(r.scratchKey.UserKey) | ||
|
|
||
| r.iter = r.iter.ResetForReuse() | ||
| return start, end, r.writer.Finish(), nil | ||
| } |
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