fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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105 lines
4.1 KiB
105 lines
4.1 KiB
// Copyright (c) 2013, 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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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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uint32_t added_to_start_; // To indicate if key is added
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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);
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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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bool whole_key_filtering_;
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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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