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36a5f8ed7f
- Replace raw slice comparison with a call to user comparator.
Added test for custom comparators.
- Fix end of namespace comments.
- Fixed bug in picking inputs for a level-0 compaction.
When finding overlapping files, the covered range may expand
as files are added to the input set. We now correctly expand
the range when this happens instead of continuing to use the
old range. For example, suppose L0 contains files with the
following ranges:
F1: a .. d
F2: c .. g
F3: f .. j
and the initial compaction target is F3. We used to search
for range f..j which yielded {F2,F3}. However we now expand
the range as soon as another file is added. In this case,
when F2 is added, we expand the range to c..j and restart the
search. That picks up file F1 as well.
This change fixes a bug related to deleted keys showing up
incorrectly after a compaction as described in Issue 44.
(Sync with upstream @25072954)
110 lines
3.6 KiB
C++
110 lines
3.6 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// BlockBuilder generates blocks where keys are prefix-compressed:
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//
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// When we store a key, we drop the prefix shared with the previous
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// string. This helps reduce the space requirement significantly.
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// Furthermore, once every K keys, we do not apply the prefix
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// compression and store the entire key. We call this a "restart
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// point". The tail end of the block stores the offsets of all of the
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// restart points, and can be used to do a binary search when looking
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// for a particular key. Values are stored as-is (without compression)
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// immediately following the corresponding key.
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//
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// An entry for a particular key-value pair has the form:
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// shared_bytes: varint32
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// unshared_bytes: varint32
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// value_length: varint32
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// key_delta: char[unshared_bytes]
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// value: char[value_length]
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// shared_bytes == 0 for restart points.
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//
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// The trailer of the block has the form:
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// restarts: uint32[num_restarts]
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// num_restarts: uint32
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// restarts[i] contains the offset within the block of the ith restart point.
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#include "table/block_builder.h"
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#include <algorithm>
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#include <assert.h>
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#include "leveldb/comparator.h"
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#include "leveldb/table_builder.h"
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#include "util/coding.h"
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namespace leveldb {
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BlockBuilder::BlockBuilder(const Options* options)
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: options_(options),
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restarts_(),
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counter_(0),
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finished_(false) {
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assert(options->block_restart_interval >= 1);
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restarts_.push_back(0); // First restart point is at offset 0
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}
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void BlockBuilder::Reset() {
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buffer_.clear();
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restarts_.clear();
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restarts_.push_back(0); // First restart point is at offset 0
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counter_ = 0;
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finished_ = false;
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last_key_.clear();
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}
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size_t BlockBuilder::CurrentSizeEstimate() const {
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return (buffer_.size() + // Raw data buffer
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restarts_.size() * sizeof(uint32_t) + // Restart array
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sizeof(uint32_t)); // Restart array length
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}
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Slice BlockBuilder::Finish() {
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// Append restart array
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for (size_t i = 0; i < restarts_.size(); i++) {
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PutFixed32(&buffer_, restarts_[i]);
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}
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PutFixed32(&buffer_, restarts_.size());
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finished_ = true;
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return Slice(buffer_);
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}
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void BlockBuilder::Add(const Slice& key, const Slice& value) {
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Slice last_key_piece(last_key_);
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assert(!finished_);
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assert(counter_ <= options_->block_restart_interval);
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assert(buffer_.empty() // No values yet?
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|| options_->comparator->Compare(key, last_key_piece) > 0);
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size_t shared = 0;
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if (counter_ < options_->block_restart_interval) {
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// See how much sharing to do with previous string
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const size_t min_length = std::min(last_key_piece.size(), key.size());
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while ((shared < min_length) && (last_key_piece[shared] == key[shared])) {
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shared++;
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}
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} else {
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// Restart compression
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restarts_.push_back(buffer_.size());
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counter_ = 0;
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}
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const size_t non_shared = key.size() - shared;
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// Add "<shared><non_shared><value_size>" to buffer_
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PutVarint32(&buffer_, shared);
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PutVarint32(&buffer_, non_shared);
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PutVarint32(&buffer_, value.size());
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// Add string delta to buffer_ followed by value
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buffer_.append(key.data() + shared, non_shared);
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buffer_.append(value.data(), value.size());
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// Update state
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last_key_.resize(shared);
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last_key_.append(key.data() + shared, non_shared);
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assert(Slice(last_key_) == key);
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counter_++;
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}
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} // namespace leveldb
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