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19ec44fd39
Summary: Add hash index support to data blocks, which helps to reduce the CPU utilization of point-lookup operations. This feature is backward compatible with the data block created without the hash index. It is disabled by default unless `BlockBasedTableOptions::data_block_index_type` is set to `data_block_index_type = kDataBlockBinaryAndHash.` The DB size would be bigger with the hash index option as a hash table is added at the end of each data block. If the hash utilization ratio is 1:1, the space overhead is one byte per key. The hash table utilization ratio is adjustable using `BlockBasedTableOptions::data_block_hash_table_util_ratio`. A lower utilization ratio will improve more on the point-lookup efficiency, but take more space too. Pull Request resolved: https://github.com/facebook/rocksdb/pull/4174 Differential Revision: D8965914 Pulled By: fgwu fbshipit-source-id: 1c6bae5d1fc39c80282d8890a72e9e67bc247198
61 lines
1.8 KiB
C++
61 lines
1.8 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root 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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#include "data_block_footer.h"
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#include "rocksdb/table.h"
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namespace rocksdb {
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const int kDataBlockIndexTypeBitShift = 31;
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// 0x7FFFFFFF
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const uint32_t kMaxNumRestarts = (1u << kDataBlockIndexTypeBitShift) - 1u;
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// 0x7FFFFFFF
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const uint32_t kNumRestartsMask = (1u << kDataBlockIndexTypeBitShift) - 1u;
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uint32_t PackIndexTypeAndNumRestarts(
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BlockBasedTableOptions::DataBlockIndexType index_type,
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uint32_t num_restarts) {
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if (num_restarts > kMaxNumRestarts) {
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assert(0); // mute travis "unused" warning
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}
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uint32_t block_footer = num_restarts;
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if (index_type == BlockBasedTableOptions::kDataBlockBinaryAndHash) {
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block_footer |= 1u << kDataBlockIndexTypeBitShift;
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} else if (index_type != BlockBasedTableOptions::kDataBlockBinarySearch) {
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assert(0);
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}
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return block_footer;
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}
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void UnPackIndexTypeAndNumRestarts(
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uint32_t block_footer,
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BlockBasedTableOptions::DataBlockIndexType* index_type,
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uint32_t* num_restarts) {
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if (index_type) {
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if (block_footer & 1u << kDataBlockIndexTypeBitShift) {
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*index_type = BlockBasedTableOptions::kDataBlockBinaryAndHash;
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} else {
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*index_type = BlockBasedTableOptions::kDataBlockBinarySearch;
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}
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}
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if (num_restarts) {
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*num_restarts = block_footer & kNumRestartsMask;
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assert(*num_restarts <= kMaxNumRestarts);
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}
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}
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} // namespace rocksdb
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