mirror of
https://github.com/facebook/rocksdb.git
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906f3dca72
Summary: this is the key component extracted from diff: https://reviews.facebook.net/D14271 I separate it to a dedicated patch to make the review easier. Test Plan: added a unit test and passed it. Reviewers: haobo, sdong, dhruba CC: leveldb Differential Revision: https://reviews.facebook.net/D16245
113 lines
3.8 KiB
C++
113 lines
3.8 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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#include <algorithm>
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#include "table/block_hash_index.h"
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#include "rocksdb/comparator.h"
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#include "rocksdb/iterator.h"
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#include "rocksdb/slice_transform.h"
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namespace rocksdb {
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BlockHashIndex* CreateBlockHashIndex(Iterator* index_iter, Iterator* data_iter,
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const uint32_t num_restarts,
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const Comparator* comparator,
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const SliceTransform* hash_key_extractor) {
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assert(hash_key_extractor);
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auto hash_index = new BlockHashIndex(hash_key_extractor);
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uint64_t current_restart_index = 0;
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std::string pending_entry_prefix;
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// pending_block_num == 0 also implies there is no entry inserted at all.
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uint32_t pending_block_num = 0;
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uint32_t pending_entry_index = 0;
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// scan all the entries and create a hash index based on their prefixes.
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data_iter->SeekToFirst();
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for (index_iter->SeekToFirst();
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index_iter->Valid() && current_restart_index < num_restarts;
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index_iter->Next()) {
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Slice last_key_in_block = index_iter->key();
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assert(data_iter->Valid() && data_iter->status().ok());
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// scan through all entries within a data block.
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while (data_iter->Valid() &&
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comparator->Compare(data_iter->key(), last_key_in_block) <= 0) {
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auto key_prefix = hash_key_extractor->Transform(data_iter->key());
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bool is_first_entry = pending_block_num == 0;
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// Keys may share the prefix
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if (is_first_entry || pending_entry_prefix != key_prefix) {
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if (!is_first_entry) {
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bool succeeded = hash_index->Add(
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pending_entry_prefix, pending_entry_index, pending_block_num);
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if (!succeeded) {
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delete hash_index;
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return nullptr;
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}
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}
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// update the status.
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// needs a hard copy otherwise the underlying data changes all the time.
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pending_entry_prefix = key_prefix.ToString();
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pending_block_num = 1;
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pending_entry_index = current_restart_index;
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} else {
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// entry number increments when keys share the prefix reside in
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// differnt data blocks.
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auto last_restart_index = pending_entry_index + pending_block_num - 1;
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assert(last_restart_index <= current_restart_index);
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if (last_restart_index != current_restart_index) {
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++pending_block_num;
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}
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}
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data_iter->Next();
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}
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++current_restart_index;
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}
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// make sure all entries has been scaned.
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assert(!index_iter->Valid());
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assert(!data_iter->Valid());
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if (pending_block_num > 0) {
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auto succeeded = hash_index->Add(pending_entry_prefix, pending_entry_index,
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pending_block_num);
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if (!succeeded) {
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delete hash_index;
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return nullptr;
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}
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}
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return hash_index;
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}
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bool BlockHashIndex::Add(const Slice& prefix, uint32_t restart_index,
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uint32_t num_blocks) {
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auto prefix_ptr = arena_.Allocate(prefix.size());
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std::copy(prefix.data() /* begin */, prefix.data() + prefix.size() /* end */,
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prefix_ptr /* destination */);
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auto result =
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restart_indices_.insert({Slice(prefix_ptr, prefix.size()),
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RestartIndex(restart_index, num_blocks)});
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return result.second;
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}
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const BlockHashIndex::RestartIndex* BlockHashIndex::GetRestartIndex(
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const Slice& key) {
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auto key_prefix = hash_key_extractor_->Transform(key);
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auto pos = restart_indices_.find(key_prefix);
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if (pos == restart_indices_.end()) {
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return nullptr;
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}
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return &pos->second;
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}
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} // namespace rocksdb
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