rocksdb/table/block_prefix_index.h

69 lines
2.2 KiB
C
Raw Normal View History

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#pragma once
#include <stdint.h>
#include "rocksdb/status.h"
namespace rocksdb {
class Comparator;
class Iterator;
class Slice;
class SliceTransform;
// Build a hash-based index to speed up the lookup for "index block".
// BlockHashIndex accepts a key and, if found, returns its restart index within
// that index block.
class BlockPrefixIndex {
public:
// Maps a key to a list of data blocks that could potentially contain
// the key, based on the prefix.
// Returns the total number of relevant blocks, 0 means the key does
// not exist.
uint32_t GetBlocks(const Slice& key, uint32_t** blocks);
size_t ApproximateMemoryUsage() const {
return sizeof(BlockPrefixIndex) +
(num_block_array_buffer_entries_ + num_buckets_) * sizeof(uint32_t);
}
// Create hash index by reading from the metadata blocks.
// @params prefixes: a sequence of prefixes.
// @params prefix_meta: contains the "metadata" to of the prefixes.
static Status Create(const SliceTransform* hash_key_extractor,
const Slice& prefixes, const Slice& prefix_meta,
BlockPrefixIndex** prefix_index);
~BlockPrefixIndex() {
delete[] buckets_;
delete[] block_array_buffer_;
}
private:
class Builder;
friend Builder;
BlockPrefixIndex(const SliceTransform* internal_prefix_extractor,
uint32_t num_buckets,
uint32_t* buckets,
uint32_t num_block_array_buffer_entries,
uint32_t* block_array_buffer)
: internal_prefix_extractor_(internal_prefix_extractor),
num_buckets_(num_buckets),
num_block_array_buffer_entries_(num_block_array_buffer_entries),
buckets_(buckets),
block_array_buffer_(block_array_buffer) {}
const SliceTransform* internal_prefix_extractor_;
uint32_t num_buckets_;
uint32_t num_block_array_buffer_entries_;
uint32_t* buckets_;
uint32_t* block_array_buffer_;
};
} // namespace rocksdb