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rocksdb/table/block_hash_index.cc

158 lines
5.0 KiB

// Copyright (c) 2013, 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.
#include "table/block_hash_index.h"
#include <algorithm>
#include "rocksdb/comparator.h"
#include "rocksdb/iterator.h"
#include "rocksdb/slice_transform.h"
#include "util/coding.h"
namespace rocksdb {
Status CreateBlockHashIndex(const SliceTransform* hash_key_extractor,
const Slice& prefixes, const Slice& prefix_meta,
BlockHashIndex** hash_index) {
uint64_t pos = 0;
auto meta_pos = prefix_meta;
Status s;
*hash_index = new BlockHashIndex(
hash_key_extractor,
false /* external module manages memory space for prefixes */);
while (!meta_pos.empty()) {
uint32_t prefix_size = 0;
uint32_t entry_index = 0;
uint32_t num_blocks = 0;
if (!GetVarint32(&meta_pos, &prefix_size) ||
!GetVarint32(&meta_pos, &entry_index) ||
!GetVarint32(&meta_pos, &num_blocks)) {
s = Status::Corruption(
"Corrupted prefix meta block: unable to read from it.");
break;
}
Slice prefix(prefixes.data() + pos, prefix_size);
(*hash_index)->Add(prefix, entry_index, num_blocks);
pos += prefix_size;
}
if (s.ok() && pos != prefixes.size()) {
s = Status::Corruption("Corrupted prefix meta block");
}
if (!s.ok()) {
delete *hash_index;
}
return s;
}
BlockHashIndex* CreateBlockHashIndexOnTheFly(
Iterator* index_iter, Iterator* data_iter, const uint32_t num_restarts,
const Comparator* comparator, const SliceTransform* hash_key_extractor) {
assert(hash_key_extractor);
auto hash_index = new BlockHashIndex(
hash_key_extractor,
true /* hash_index will copy prefix when Add() is called */);
uint32_t current_restart_index = 0;
std::string pending_entry_prefix;
// pending_block_num == 0 also implies there is no entry inserted at all.
uint32_t pending_block_num = 0;
uint32_t pending_entry_index = 0;
// scan all the entries and create a hash index based on their prefixes.
data_iter->SeekToFirst();
for (index_iter->SeekToFirst();
index_iter->Valid() && current_restart_index < num_restarts;
index_iter->Next()) {
Slice last_key_in_block = index_iter->key();
assert(data_iter->Valid() && data_iter->status().ok());
// scan through all entries within a data block.
while (data_iter->Valid() &&
comparator->Compare(data_iter->key(), last_key_in_block) <= 0) {
auto key_prefix = hash_key_extractor->Transform(data_iter->key());
bool is_first_entry = pending_block_num == 0;
// Keys may share the prefix
if (is_first_entry || pending_entry_prefix != key_prefix) {
if (!is_first_entry) {
bool succeeded = hash_index->Add(
pending_entry_prefix, pending_entry_index, pending_block_num);
if (!succeeded) {
delete hash_index;
return nullptr;
}
}
// update the status.
// needs a hard copy otherwise the underlying data changes all the time.
pending_entry_prefix = key_prefix.ToString();
pending_block_num = 1;
pending_entry_index = current_restart_index;
} else {
// entry number increments when keys share the prefix reside in
10 years ago
// different data blocks.
auto last_restart_index = pending_entry_index + pending_block_num - 1;
assert(last_restart_index <= current_restart_index);
if (last_restart_index != current_restart_index) {
++pending_block_num;
}
}
data_iter->Next();
}
++current_restart_index;
}
// make sure all entries has been scaned.
assert(!index_iter->Valid());
assert(!data_iter->Valid());
if (pending_block_num > 0) {
auto succeeded = hash_index->Add(pending_entry_prefix, pending_entry_index,
pending_block_num);
if (!succeeded) {
delete hash_index;
return nullptr;
}
}
return hash_index;
}
bool BlockHashIndex::Add(const Slice& prefix, uint32_t restart_index,
uint32_t num_blocks) {
auto prefix_to_insert = prefix;
if (kOwnPrefixes) {
auto prefix_ptr = arena_.Allocate(prefix.size());
std::copy(prefix.data() /* begin */,
prefix.data() + prefix.size() /* end */,
prefix_ptr /* destination */);
prefix_to_insert = Slice(prefix_ptr, prefix.size());
}
auto result = restart_indices_.insert(
{prefix_to_insert, RestartIndex(restart_index, num_blocks)});
return result.second;
}
const BlockHashIndex::RestartIndex* BlockHashIndex::GetRestartIndex(
const Slice& key) {
auto key_prefix = hash_key_extractor_->Transform(key);
auto pos = restart_indices_.find(key_prefix);
if (pos == restart_indices_.end()) {
return nullptr;
}
return &pos->second;
}
} // namespace rocksdb