mirror of https://github.com/facebook/rocksdb.git
69 lines
2.2 KiB
C++
69 lines
2.2 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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#pragma once
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#include <stdint.h>
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#include "rocksdb/status.h"
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namespace rocksdb {
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class Comparator;
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class Iterator;
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class Slice;
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class SliceTransform;
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// Build a hash-based index to speed up the lookup for "index block".
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// BlockHashIndex accepts a key and, if found, returns its restart index within
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// that index block.
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class BlockPrefixIndex {
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public:
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// Maps a key to a list of data blocks that could potentially contain
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// the key, based on the prefix.
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// Returns the total number of relevant blocks, 0 means the key does
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// not exist.
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uint32_t GetBlocks(const Slice& key, uint32_t** blocks);
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size_t ApproximateMemoryUsage() const {
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return sizeof(BlockPrefixIndex) +
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(num_block_array_buffer_entries_ + num_buckets_) * sizeof(uint32_t);
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}
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// Create hash index by reading from the metadata blocks.
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// @params prefixes: a sequence of prefixes.
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// @params prefix_meta: contains the "metadata" to of the prefixes.
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static Status Create(const SliceTransform* hash_key_extractor,
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const Slice& prefixes, const Slice& prefix_meta,
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BlockPrefixIndex** prefix_index);
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~BlockPrefixIndex() {
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delete[] buckets_;
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delete[] block_array_buffer_;
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}
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private:
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class Builder;
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friend Builder;
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BlockPrefixIndex(const SliceTransform* internal_prefix_extractor,
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uint32_t num_buckets,
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uint32_t* buckets,
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uint32_t num_block_array_buffer_entries,
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uint32_t* block_array_buffer)
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: internal_prefix_extractor_(internal_prefix_extractor),
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num_buckets_(num_buckets),
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num_block_array_buffer_entries_(num_block_array_buffer_entries),
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buckets_(buckets),
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block_array_buffer_(block_array_buffer) {}
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const SliceTransform* internal_prefix_extractor_;
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uint32_t num_buckets_;
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uint32_t num_block_array_buffer_entries_;
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uint32_t* buckets_;
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uint32_t* block_array_buffer_;
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};
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} // namespace rocksdb
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