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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <stdint.h>
#include "db/dbformat.h"
#include "rocksdb/status.h"
namespace ROCKSDB_NAMESPACE {
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.
// Note: table reader (caller) is responsible for keeping shared_ptr to
// underlying prefix extractor
// @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* prefix_extractor, uint32_t num_buckets,
uint32_t* buckets, uint32_t num_block_array_buffer_entries,
uint32_t* block_array_buffer)
: internal_prefix_extractor_(prefix_extractor),
num_buckets_(num_buckets),
num_block_array_buffer_entries_(num_block_array_buffer_entries),
buckets_(buckets),
block_array_buffer_(block_array_buffer) {}
InternalKeySliceTransform internal_prefix_extractor_;
uint32_t num_buckets_;
uint32_t num_block_array_buffer_entries_;
uint32_t* buckets_;
uint32_t* block_array_buffer_;
};
} // namespace ROCKSDB_NAMESPACE
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