mirror of https://github.com/facebook/rocksdb.git
91 lines
3.1 KiB
C++
91 lines
3.1 KiB
C++
// 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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//
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// It is a base class for BlockBasedFilter and FullFilter.
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// These two are both used in BlockBasedTable. The first one contain filter
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// For a part of keys in sst file, the second contain filter for all keys
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// in sst file.
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#pragma once
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#include <memory>
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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 <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 "rocksdb/table.h"
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#include "util/hash.h"
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#include "format.h"
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namespace rocksdb {
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const uint64_t kNotValid = ULLONG_MAX;
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class FilterPolicy;
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// A FilterBlockBuilder 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 FilterBlockBuilder must match the regexp:
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// (StartBlock Add*)* Finish
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//
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// BlockBased/Full FilterBlock would be called in the same way.
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class FilterBlockBuilder {
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public:
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explicit FilterBlockBuilder() {}
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virtual ~FilterBlockBuilder() {}
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virtual bool IsBlockBased() = 0; // If is blockbased filter
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virtual void StartBlock(uint64_t block_offset) = 0; // Start new block filter
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virtual void Add(const Slice& key) = 0; // Add a key to current filter
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virtual Slice Finish() = 0; // Generate Filter
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private:
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// No copying allowed
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FilterBlockBuilder(const FilterBlockBuilder&);
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void operator=(const FilterBlockBuilder&);
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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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//
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// BlockBased/Full FilterBlock would be called in the same way.
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class FilterBlockReader {
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public:
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explicit FilterBlockReader() {}
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virtual ~FilterBlockReader() {}
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virtual bool IsBlockBased() = 0; // If is blockbased filter
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virtual bool KeyMayMatch(const Slice& key,
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uint64_t block_offset = kNotValid) = 0;
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virtual bool PrefixMayMatch(const Slice& prefix,
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uint64_t block_offset = kNotValid) = 0;
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virtual size_t ApproximateMemoryUsage() const = 0;
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// convert this object to a human readable form
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virtual std::string ToString() const {
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std::string error_msg("Unsupported filter \n");
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return error_msg;
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}
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private:
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// No copying allowed
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FilterBlockReader(const FilterBlockReader&);
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void operator=(const FilterBlockReader&);
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};
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} // namespace rocksdb
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