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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).
#ifndef ROCKSDB_LITE
#include "table/plain/plain_table_index.h"
#include <cinttypes>
#include "logging/logging.h"
#include "util/coding.h"
#include "util/hash.h"
namespace ROCKSDB_NAMESPACE {
namespace {
inline uint32_t GetBucketIdFromHash(uint32_t hash, uint32_t num_buckets) {
assert(num_buckets > 0);
return hash % num_buckets;
}
} // namespace
Status PlainTableIndex::InitFromRawData(Slice data) {
if (!GetVarint32(&data, &index_size_)) {
return Status::Corruption("Couldn't read the index size!");
}
assert(index_size_ > 0);
if (!GetVarint32(&data, &num_prefixes_)) {
return Status::Corruption("Couldn't read the index size!");
}
sub_index_size_ =
static_cast<uint32_t>(data.size()) - index_size_ * kOffsetLen;
char* index_data_begin = const_cast<char*>(data.data());
index_ = reinterpret_cast<uint32_t*>(index_data_begin);
sub_index_ = reinterpret_cast<char*>(index_ + index_size_);
return Status::OK();
}
PlainTableIndex::IndexSearchResult PlainTableIndex::GetOffset(
uint32_t prefix_hash, uint32_t* bucket_value) const {
int bucket = GetBucketIdFromHash(prefix_hash, index_size_);
GetUnaligned(index_ + bucket, bucket_value);
if ((*bucket_value & kSubIndexMask) == kSubIndexMask) {
*bucket_value ^= kSubIndexMask;
return kSubindex;
}
if (*bucket_value >= kMaxFileSize) {
return kNoPrefixForBucket;
} else {
// point directly to the file
return kDirectToFile;
}
}
void PlainTableIndexBuilder::IndexRecordList::AddRecord(uint32_t hash,
uint32_t offset) {
if (num_records_in_current_group_ == kNumRecordsPerGroup) {
current_group_ = AllocateNewGroup();
num_records_in_current_group_ = 0;
}
auto& new_record = current_group_[num_records_in_current_group_++];
new_record.hash = hash;
new_record.offset = offset;
new_record.next = nullptr;
}
void PlainTableIndexBuilder::AddKeyPrefix(Slice key_prefix_slice,
uint32_t key_offset) {
if (is_first_record_ || prev_key_prefix_ != key_prefix_slice.ToString()) {
++num_prefixes_;
if (!is_first_record_) {
keys_per_prefix_hist_.Add(num_keys_per_prefix_);
}
num_keys_per_prefix_ = 0;
prev_key_prefix_ = key_prefix_slice.ToString();
prev_key_prefix_hash_ = GetSliceHash(key_prefix_slice);
due_index_ = true;
}
if (due_index_) {
// Add an index key for every kIndexIntervalForSamePrefixKeys keys
record_list_.AddRecord(prev_key_prefix_hash_, key_offset);
due_index_ = false;
}
num_keys_per_prefix_++;
if (index_sparseness_ == 0 || num_keys_per_prefix_ % index_sparseness_ == 0) {
due_index_ = true;
}
is_first_record_ = false;
}
Slice PlainTableIndexBuilder::Finish() {
AllocateIndex();
std::vector<IndexRecord*> hash_to_offsets(index_size_, nullptr);
std::vector<uint32_t> entries_per_bucket(index_size_, 0);
BucketizeIndexes(&hash_to_offsets, &entries_per_bucket);
keys_per_prefix_hist_.Add(num_keys_per_prefix_);
ROCKS_LOG_INFO(ioptions_.logger, "Number of Keys per prefix Histogram: %s",
keys_per_prefix_hist_.ToString().c_str());
// From the temp data structure, populate indexes.
return FillIndexes(hash_to_offsets, entries_per_bucket);
}
void PlainTableIndexBuilder::AllocateIndex() {
if (prefix_extractor_ == nullptr || hash_table_ratio_ <= 0) {
// Fall back to pure binary search if the user fails to specify a prefix
// extractor.
index_size_ = 1;
} else {
double hash_table_size_multipier = 1.0 / hash_table_ratio_;
index_size_ =
static_cast<uint32_t>(num_prefixes_ * hash_table_size_multipier) + 1;
assert(index_size_ > 0);
}
}
void PlainTableIndexBuilder::BucketizeIndexes(
std::vector<IndexRecord*>* hash_to_offsets,
std::vector<uint32_t>* entries_per_bucket) {
bool first = true;
uint32_t prev_hash = 0;
size_t num_records = record_list_.GetNumRecords();
for (size_t i = 0; i < num_records; i++) {
IndexRecord* index_record = record_list_.At(i);
uint32_t cur_hash = index_record->hash;
if (first || prev_hash != cur_hash) {
prev_hash = cur_hash;
first = false;
}
uint32_t bucket = GetBucketIdFromHash(cur_hash, index_size_);
IndexRecord* prev_bucket_head = (*hash_to_offsets)[bucket];
index_record->next = prev_bucket_head;
(*hash_to_offsets)[bucket] = index_record;
(*entries_per_bucket)[bucket]++;
}
sub_index_size_ = 0;
for (auto entry_count : *entries_per_bucket) {
if (entry_count <= 1) {
continue;
}
// Only buckets with more than 1 entry will have subindex.
sub_index_size_ += VarintLength(entry_count);
// total bytes needed to store these entries' in-file offsets.
sub_index_size_ += entry_count * PlainTableIndex::kOffsetLen;
}
}
Slice PlainTableIndexBuilder::FillIndexes(
const std::vector<IndexRecord*>& hash_to_offsets,
const std::vector<uint32_t>& entries_per_bucket) {
ROCKS_LOG_DEBUG(ioptions_.logger,
"Reserving %" PRIu32 " bytes for plain table's sub_index",
sub_index_size_);
auto total_allocate_size = GetTotalSize();
char* allocated = arena_->AllocateAligned(
total_allocate_size, huge_page_tlb_size_, ioptions_.logger);
auto temp_ptr = EncodeVarint32(allocated, index_size_);
uint32_t* index =
reinterpret_cast<uint32_t*>(EncodeVarint32(temp_ptr, num_prefixes_));
char* sub_index = reinterpret_cast<char*>(index + index_size_);
uint32_t sub_index_offset = 0;
for (uint32_t i = 0; i < index_size_; i++) {
uint32_t num_keys_for_bucket = entries_per_bucket[i];
switch (num_keys_for_bucket) {
case 0:
// No key for bucket
PutUnaligned(index + i, (uint32_t)PlainTableIndex::kMaxFileSize);
break;
case 1:
// point directly to the file offset
PutUnaligned(index + i, hash_to_offsets[i]->offset);
break;
default:
// point to second level indexes.
PutUnaligned(index + i,
sub_index_offset | PlainTableIndex::kSubIndexMask);
char* prev_ptr = &sub_index[sub_index_offset];
char* cur_ptr = EncodeVarint32(prev_ptr, num_keys_for_bucket);
sub_index_offset += static_cast<uint32_t>(cur_ptr - prev_ptr);
char* sub_index_pos = &sub_index[sub_index_offset];
IndexRecord* record = hash_to_offsets[i];
int j;
for (j = num_keys_for_bucket - 1; j >= 0 && record;
j--, record = record->next) {
EncodeFixed32(sub_index_pos + j * sizeof(uint32_t), record->offset);
}
assert(j == -1 && record == nullptr);
sub_index_offset += PlainTableIndex::kOffsetLen * num_keys_for_bucket;
assert(sub_index_offset <= sub_index_size_);
break;
}
}
assert(sub_index_offset == sub_index_size_);
ROCKS_LOG_DEBUG(ioptions_.logger,
"hash table size: %" PRIu32 ", suffix_map length %" PRIu32,
index_size_, sub_index_size_);
return Slice(allocated, GetTotalSize());
}
const std::string PlainTableIndexBuilder::kPlainTableIndexBlock =
"PlainTableIndexBlock";
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE
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