0f0076ed5a
Summary: Currently, the in-memory hash index of blockbased table uses a precise hash map to track the prefix to block range mapping. In some use cases, especially when prefix itself is big, the memory overhead becomes a problem. This diff introduces a fixed hash bucket array that does not store the prefix and allows prefix collision, which is similar to the plaintable hash index, in order to reduce the memory consumption. Just a quick draft, still testing and refining. Test Plan: unit test and shadow testing Reviewers: dhruba, kailiu, sdong Reviewed By: sdong Subscribers: leveldb Differential Revision: https://reviews.facebook.net/D19047
65 lines
2.0 KiB
C++
65 lines
2.0 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) 2011 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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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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#include "rocksdb/iterator.h"
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#include "rocksdb/options.h"
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namespace rocksdb {
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struct BlockContents;
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class Comparator;
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class BlockHashIndex;
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class BlockPrefixIndex;
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class Block {
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public:
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// Initialize the block with the specified contents.
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explicit Block(const BlockContents& contents);
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~Block();
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size_t size() const { return size_; }
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const char* data() const { return data_; }
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bool cachable() const { return cachable_; }
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uint32_t NumRestarts() const;
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CompressionType compression_type() const { return compression_type_; }
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// If hash index lookup is enabled and `use_hash_index` is true. This block
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// will do hash lookup for the key prefix.
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//
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// NOTE: for the hash based lookup, if a key prefix doesn't match any key,
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// the iterator will simply be set as "invalid", rather than returning
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// the key that is just pass the target key.
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Iterator* NewIterator(const Comparator* comparator);
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void SetBlockHashIndex(BlockHashIndex* hash_index);
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void SetBlockPrefixIndex(BlockPrefixIndex* prefix_index);
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private:
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const char* data_;
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size_t size_;
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uint32_t restart_offset_; // Offset in data_ of restart array
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bool owned_; // Block owns data_[]
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bool cachable_;
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CompressionType compression_type_;
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std::unique_ptr<BlockHashIndex> hash_index_;
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std::unique_ptr<BlockPrefixIndex> prefix_index_;
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// No copying allowed
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Block(const Block&);
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void operator=(const Block&);
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class Iter;
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};
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} // namespace rocksdb
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