fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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251 lines
8.0 KiB
251 lines
8.0 KiB
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2012 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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#include "table/block_based_filter_block.h"
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#include <algorithm>
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#include "db/dbformat.h"
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#include "rocksdb/filter_policy.h"
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#include "util/coding.h"
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#include "util/perf_context_imp.h"
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#include "util/string_util.h"
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namespace rocksdb {
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namespace {
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void AppendItem(std::string* props, const std::string& key,
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const std::string& value) {
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char cspace = ' ';
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std::string value_str("");
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size_t i = 0;
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const size_t dataLength = 64;
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const size_t tabLength = 2;
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const size_t offLength = 16;
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value_str.append(&value[i], std::min(size_t(dataLength), value.size()));
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i += dataLength;
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while (i < value.size()) {
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value_str.append("\n");
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value_str.append(offLength, cspace);
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value_str.append(&value[i], std::min(size_t(dataLength), value.size() - i));
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i += dataLength;
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}
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std::string result("");
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if (key.size() < (offLength - tabLength))
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result.append(size_t((offLength - tabLength)) - key.size(), cspace);
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result.append(key);
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props->append(result + ": " + value_str + "\n");
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}
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template <class TKey>
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void AppendItem(std::string* props, const TKey& key, const std::string& value) {
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std::string key_str = rocksdb::ToString(key);
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AppendItem(props, key_str, value);
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}
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} // namespace
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// See doc/table_format.txt for an explanation of the filter block format.
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// Generate new filter every 2KB of data
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static const size_t kFilterBaseLg = 11;
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static const size_t kFilterBase = 1 << kFilterBaseLg;
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BlockBasedFilterBlockBuilder::BlockBasedFilterBlockBuilder(
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const SliceTransform* prefix_extractor,
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const BlockBasedTableOptions& table_opt)
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: policy_(table_opt.filter_policy.get()),
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prefix_extractor_(prefix_extractor),
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whole_key_filtering_(table_opt.whole_key_filtering),
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prev_prefix_start_(0),
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prev_prefix_size_(0) {
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assert(policy_);
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}
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void BlockBasedFilterBlockBuilder::StartBlock(uint64_t block_offset) {
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uint64_t filter_index = (block_offset / kFilterBase);
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assert(filter_index >= filter_offsets_.size());
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while (filter_index > filter_offsets_.size()) {
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GenerateFilter();
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}
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}
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void BlockBasedFilterBlockBuilder::Add(const Slice& key) {
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if (prefix_extractor_ && prefix_extractor_->InDomain(key)) {
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AddPrefix(key);
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}
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if (whole_key_filtering_) {
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AddKey(key);
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}
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}
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// Add key to filter if needed
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inline void BlockBasedFilterBlockBuilder::AddKey(const Slice& key) {
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start_.push_back(entries_.size());
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entries_.append(key.data(), key.size());
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}
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// Add prefix to filter if needed
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inline void BlockBasedFilterBlockBuilder::AddPrefix(const Slice& key) {
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// get slice for most recently added entry
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Slice prev;
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if (prev_prefix_size_ > 0) {
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prev = Slice(entries_.data() + prev_prefix_start_, prev_prefix_size_);
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}
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Slice prefix = prefix_extractor_->Transform(key);
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// insert prefix only when it's different from the previous prefix.
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if (prev.size() == 0 || prefix != prev) {
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start_.push_back(entries_.size());
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prev_prefix_start_ = entries_.size();
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prev_prefix_size_ = prefix.size();
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entries_.append(prefix.data(), prefix.size());
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}
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}
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Slice BlockBasedFilterBlockBuilder::Finish() {
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if (!start_.empty()) {
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GenerateFilter();
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}
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// Append array of per-filter offsets
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const uint32_t array_offset = static_cast<uint32_t>(result_.size());
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for (size_t i = 0; i < filter_offsets_.size(); i++) {
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PutFixed32(&result_, filter_offsets_[i]);
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}
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PutFixed32(&result_, array_offset);
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result_.push_back(kFilterBaseLg); // Save encoding parameter in result
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return Slice(result_);
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}
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void BlockBasedFilterBlockBuilder::GenerateFilter() {
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const size_t num_entries = start_.size();
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if (num_entries == 0) {
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// Fast path if there are no keys for this filter
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filter_offsets_.push_back(static_cast<uint32_t>(result_.size()));
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return;
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}
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// Make list of keys from flattened key structure
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start_.push_back(entries_.size()); // Simplify length computation
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tmp_entries_.resize(num_entries);
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for (size_t i = 0; i < num_entries; i++) {
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const char* base = entries_.data() + start_[i];
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size_t length = start_[i + 1] - start_[i];
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tmp_entries_[i] = Slice(base, length);
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}
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// Generate filter for current set of keys and append to result_.
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filter_offsets_.push_back(static_cast<uint32_t>(result_.size()));
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policy_->CreateFilter(&tmp_entries_[0], static_cast<int>(num_entries),
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&result_);
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tmp_entries_.clear();
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entries_.clear();
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start_.clear();
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prev_prefix_start_ = 0;
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prev_prefix_size_ = 0;
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}
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BlockBasedFilterBlockReader::BlockBasedFilterBlockReader(
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const SliceTransform* prefix_extractor,
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const BlockBasedTableOptions& table_opt, bool whole_key_filtering,
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BlockContents&& contents, Statistics* stats)
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: FilterBlockReader(contents.data.size(), stats),
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policy_(table_opt.filter_policy.get()),
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prefix_extractor_(prefix_extractor),
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whole_key_filtering_(whole_key_filtering),
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data_(nullptr),
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offset_(nullptr),
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num_(0),
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base_lg_(0),
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contents_(std::move(contents)) {
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assert(policy_);
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size_t n = contents_.data.size();
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if (n < 5) return; // 1 byte for base_lg_ and 4 for start of offset array
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base_lg_ = contents_.data[n - 1];
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uint32_t last_word = DecodeFixed32(contents_.data.data() + n - 5);
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if (last_word > n - 5) return;
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data_ = contents_.data.data();
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offset_ = data_ + last_word;
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num_ = (n - 5 - last_word) / 4;
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}
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bool BlockBasedFilterBlockReader::KeyMayMatch(const Slice& key,
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uint64_t block_offset) {
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assert(block_offset != kNotValid);
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if (!whole_key_filtering_) {
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return true;
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}
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return MayMatch(key, block_offset);
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}
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bool BlockBasedFilterBlockReader::PrefixMayMatch(const Slice& prefix,
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uint64_t block_offset) {
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assert(block_offset != kNotValid);
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if (!prefix_extractor_) {
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return true;
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}
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return MayMatch(prefix, block_offset);
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}
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bool BlockBasedFilterBlockReader::MayMatch(const Slice& entry,
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uint64_t block_offset) {
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uint64_t index = block_offset >> base_lg_;
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if (index < num_) {
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uint32_t start = DecodeFixed32(offset_ + index * 4);
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uint32_t limit = DecodeFixed32(offset_ + index * 4 + 4);
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if (start <= limit && limit <= (uint32_t)(offset_ - data_)) {
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Slice filter = Slice(data_ + start, limit - start);
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bool const may_match = policy_->KeyMayMatch(entry, filter);
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if (may_match) {
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PERF_COUNTER_ADD(bloom_sst_hit_count, 1);
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return true;
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} else {
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PERF_COUNTER_ADD(bloom_sst_miss_count, 1);
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return false;
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}
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} else if (start == limit) {
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// Empty filters do not match any entries
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return false;
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}
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}
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return true; // Errors are treated as potential matches
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}
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size_t BlockBasedFilterBlockReader::ApproximateMemoryUsage() const {
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return num_ * 4 + 5 + (offset_ - data_);
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}
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std::string BlockBasedFilterBlockReader::ToString() const {
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std::string result, filter_meta;
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result.reserve(1024);
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std::string s_bo("Block offset"), s_hd("Hex dump"), s_fb("# filter blocks");
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AppendItem(&result, s_fb, rocksdb::ToString(num_));
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AppendItem(&result, s_bo, s_hd);
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for (size_t index = 0; index < num_; index++) {
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uint32_t start = DecodeFixed32(offset_ + index * 4);
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uint32_t limit = DecodeFixed32(offset_ + index * 4 + 4);
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if (start != limit) {
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result.append(" filter block # " + rocksdb::ToString(index + 1) + "\n");
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Slice filter = Slice(data_ + start, limit - start);
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AppendItem(&result, start, filter.ToString(true));
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}
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}
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return result;
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}
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} // namespace rocksdb
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