5009b5326b
Summary: Currently, if users define both of full key bloom and prefix bloom in SST files. During Get(), if full key bloom shows the key may exist, we still go ahead and check prefix bloom. This is wasteful. If bloom filter for full keys exists, we should always ignore prefix bloom in Get(). Test Plan: Run existing tests Reviewers: yhchiang, IslamAbdelRahman Reviewed By: IslamAbdelRahman Subscribers: leveldb, andrewkr, dhruba Differential Revision: https://reviews.facebook.net/D57825
108 lines
4.3 KiB
C++
108 lines
4.3 KiB
C++
// 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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//
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// A filter block is stored near the end of a Table file. It contains
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// filters (e.g., bloom filters) for all data blocks in the table combined
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// into a single filter block.
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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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#include <string>
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#include <memory>
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#include <vector>
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#include "rocksdb/options.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/slice_transform.h"
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#include "table/filter_block.h"
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#include "util/hash.h"
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namespace rocksdb {
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// A BlockBasedFilterBlockBuilder is used to construct all of the filters for a
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// particular Table. It generates a single string which is stored as
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// a special block in the Table.
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//
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// The sequence of calls to BlockBasedFilterBlockBuilder must match the regexp:
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// (StartBlock Add*)* Finish
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class BlockBasedFilterBlockBuilder : public FilterBlockBuilder {
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public:
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BlockBasedFilterBlockBuilder(const SliceTransform* prefix_extractor,
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const BlockBasedTableOptions& table_opt);
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virtual bool IsBlockBased() override { return true; }
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virtual void StartBlock(uint64_t block_offset) override;
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virtual void Add(const Slice& key) override;
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virtual Slice Finish() override;
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private:
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void AddKey(const Slice& key);
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void AddPrefix(const Slice& key);
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void GenerateFilter();
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// important: all of these might point to invalid addresses
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// at the time of destruction of this filter block. destructor
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// should NOT dereference them.
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const FilterPolicy* policy_;
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const SliceTransform* prefix_extractor_;
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bool whole_key_filtering_;
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size_t prev_prefix_start_; // the position of the last appended prefix
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// to "entries_".
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size_t prev_prefix_size_; // the length of the last appended prefix to
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// "entries_".
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std::string entries_; // Flattened entry contents
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std::vector<size_t> start_; // Starting index in entries_ of each entry
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std::string result_; // Filter data computed so far
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std::vector<Slice> tmp_entries_; // policy_->CreateFilter() argument
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std::vector<uint32_t> filter_offsets_;
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// No copying allowed
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BlockBasedFilterBlockBuilder(const BlockBasedFilterBlockBuilder&);
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void operator=(const BlockBasedFilterBlockBuilder&);
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};
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// A FilterBlockReader is used to parse filter from SST table.
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// KeyMayMatch and PrefixMayMatch would trigger filter checking
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class BlockBasedFilterBlockReader : public FilterBlockReader {
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public:
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// REQUIRES: "contents" and *policy must stay live while *this is live.
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BlockBasedFilterBlockReader(const SliceTransform* prefix_extractor,
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const BlockBasedTableOptions& table_opt,
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bool whole_key_filtering,
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BlockContents&& contents, Statistics* statistics);
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virtual bool IsBlockBased() override { return true; }
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virtual bool KeyMayMatch(const Slice& key,
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uint64_t block_offset = kNotValid) override;
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virtual bool PrefixMayMatch(const Slice& prefix,
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uint64_t block_offset = kNotValid) override;
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virtual size_t ApproximateMemoryUsage() const override;
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// convert this object to a human readable form
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std::string ToString() const override;
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private:
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const FilterPolicy* policy_;
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const SliceTransform* prefix_extractor_;
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const char* data_; // Pointer to filter data (at block-start)
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const char* offset_; // Pointer to beginning of offset array (at block-end)
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size_t num_; // Number of entries in offset array
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size_t base_lg_; // Encoding parameter (see kFilterBaseLg in .cc file)
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BlockContents contents_;
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bool MayMatch(const Slice& entry, uint64_t block_offset);
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// No copying allowed
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BlockBasedFilterBlockReader(const BlockBasedFilterBlockReader&);
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void operator=(const BlockBasedFilterBlockReader&);
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};
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} // namespace rocksdb
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