https://github.com/facebook/rocksdb
Tip revision: 3a0bf873b544794b79e67245c775a9e265be8d47 authored by Yueh-Hsuan Chiang on 08 October 2015, 18:15:18 UTC
Change RocksDB version to 4.1
Change RocksDB version to 4.1
Tip revision: 3a0bf87
block_based_filter_block.h
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// A filter block is stored near the end of a Table file. It contains
// filters (e.g., bloom filters) for all data blocks in the table combined
// into a single filter block.
#pragma once
#include <stddef.h>
#include <stdint.h>
#include <string>
#include <memory>
#include <vector>
#include "rocksdb/options.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "table/filter_block.h"
#include "util/hash.h"
namespace rocksdb {
// A BlockBasedFilterBlockBuilder is used to construct all of the filters for a
// particular Table. It generates a single string which is stored as
// a special block in the Table.
//
// The sequence of calls to BlockBasedFilterBlockBuilder must match the regexp:
// (StartBlock Add*)* Finish
class BlockBasedFilterBlockBuilder : public FilterBlockBuilder {
public:
BlockBasedFilterBlockBuilder(const SliceTransform* prefix_extractor,
const BlockBasedTableOptions& table_opt);
virtual bool IsBlockBased() override { return true; }
virtual void StartBlock(uint64_t block_offset) override;
virtual void Add(const Slice& key) override;
virtual Slice Finish() override;
private:
void AddKey(const Slice& key);
void AddPrefix(const Slice& key);
void GenerateFilter();
// important: all of these might point to invalid addresses
// at the time of destruction of this filter block. destructor
// should NOT dereference them.
const FilterPolicy* policy_;
const SliceTransform* prefix_extractor_;
bool whole_key_filtering_;
std::string entries_; // Flattened entry contents
std::vector<size_t> start_; // Starting index in entries_ of each entry
uint32_t added_to_start_; // To indicate if key is added
std::string result_; // Filter data computed so far
std::vector<Slice> tmp_entries_; // policy_->CreateFilter() argument
std::vector<uint32_t> filter_offsets_;
// No copying allowed
BlockBasedFilterBlockBuilder(const BlockBasedFilterBlockBuilder&);
void operator=(const BlockBasedFilterBlockBuilder&);
};
// A FilterBlockReader is used to parse filter from SST table.
// KeyMayMatch and PrefixMayMatch would trigger filter checking
class BlockBasedFilterBlockReader : public FilterBlockReader {
public:
// REQUIRES: "contents" and *policy must stay live while *this is live.
BlockBasedFilterBlockReader(const SliceTransform* prefix_extractor,
const BlockBasedTableOptions& table_opt,
bool whole_key_filtering,
BlockContents&& contents);
virtual bool IsBlockBased() override { return true; }
virtual bool KeyMayMatch(const Slice& key,
uint64_t block_offset = kNotValid) override;
virtual bool PrefixMayMatch(const Slice& prefix,
uint64_t block_offset = kNotValid) override;
virtual size_t ApproximateMemoryUsage() const override;
// convert this object to a human readable form
std::string ToString() const override;
private:
const FilterPolicy* policy_;
const SliceTransform* prefix_extractor_;
bool whole_key_filtering_;
const char* data_; // Pointer to filter data (at block-start)
const char* offset_; // Pointer to beginning of offset array (at block-end)
size_t num_; // Number of entries in offset array
size_t base_lg_; // Encoding parameter (see kFilterBaseLg in .cc file)
BlockContents contents_;
bool MayMatch(const Slice& entry, uint64_t block_offset);
// No copying allowed
BlockBasedFilterBlockReader(const BlockBasedFilterBlockReader&);
void operator=(const BlockBasedFilterBlockReader&);
};
} // namespace rocksdb