mirror of https://github.com/facebook/rocksdb.git
649 lines
20 KiB
C++
649 lines
20 KiB
C++
// 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 "table/plain_table_reader.h"
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#include <unordered_map>
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#include <map>
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#include "db/dbformat.h"
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#include "rocksdb/cache.h"
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#include "rocksdb/comparator.h"
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#include "rocksdb/env.h"
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#include "rocksdb/filter_policy.h"
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#include "rocksdb/options.h"
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#include "rocksdb/statistics.h"
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#include "rocksdb/plain_table_factory.h"
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#include "table/block.h"
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#include "table/filter_block.h"
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#include "table/format.h"
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#include "table/meta_blocks.h"
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#include "table/two_level_iterator.h"
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#include "util/coding.h"
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#include "util/dynamic_bloom.h"
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#include "util/hash.h"
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#include "util/histogram.h"
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#include "util/murmurhash.h"
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#include "util/perf_context_imp.h"
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#include "util/stop_watch.h"
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namespace rocksdb {
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extern const uint64_t kPlainTableMagicNumber;
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static uint32_t GetSliceHash(Slice const& s) {
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return Hash(s.data(), s.size(), 397) ;
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}
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static uint32_t getBucketIdFromHash(uint32_t hash, uint32_t num_buckets) {
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return hash % num_buckets;
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}
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PlainTableReader::PlainTableReader(const EnvOptions& storage_options,
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uint64_t file_size, int bloom_bits_per_key,
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double hash_table_ratio,
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const TableProperties& table_properties) :
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hash_table_size_(0), soptions_(storage_options), file_size_(file_size),
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hash_table_ratio_(hash_table_ratio),
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bloom_bits_per_key_(bloom_bits_per_key),
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table_properties_(table_properties), data_start_offset_(0),
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data_end_offset_(table_properties_.data_size),
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user_key_len_(table_properties.fixed_key_len) {
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hash_table_ = nullptr;
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bloom_ = nullptr;
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sub_index_ = nullptr;
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}
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PlainTableReader::~PlainTableReader() {
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delete[] hash_table_;
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delete[] sub_index_;
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delete bloom_;
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}
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Status PlainTableReader::Open(const Options& options,
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const EnvOptions& soptions,
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unique_ptr<RandomAccessFile> && file,
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uint64_t file_size,
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unique_ptr<TableReader>* table_reader,
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const int bloom_num_bits,
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double hash_table_ratio) {
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assert(options.allow_mmap_reads);
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if (file_size > 2147483646) {
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return Status::NotSupported("File is too large for PlainTableReader!");
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}
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TableProperties table_properties;
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auto s = ReadTableProperties(
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file.get(),
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file_size,
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kPlainTableMagicNumber,
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options.env,
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options.info_log.get(),
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&table_properties
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);
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if (!s.ok()) {
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return s;
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}
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std::unique_ptr<PlainTableReader> new_reader(new PlainTableReader(
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soptions,
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file_size,
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bloom_num_bits,
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hash_table_ratio,
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table_properties
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));
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new_reader->file_ = std::move(file);
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new_reader->options_ = options;
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// -- Populate Index
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s = new_reader->PopulateIndex();
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if (!s.ok()) {
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return s;
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}
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*table_reader = std::move(new_reader);
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return s;
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}
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void PlainTableReader::SetupForCompaction() {
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}
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bool PlainTableReader::PrefixMayMatch(const Slice& internal_prefix) {
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return true;
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}
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Iterator* PlainTableReader::NewIterator(const ReadOptions& options) {
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return new PlainTableIterator(this);
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}
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struct PlainTableReader::IndexRecord {
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uint32_t hash; // hash of the prefix
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uint32_t offset; // offset of a row
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IndexRecord* next;
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};
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// Helper class to track all the index records
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class PlainTableReader::IndexRecordList {
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public:
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explicit IndexRecordList(size_t num_records_per_group) :
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num_records_per_group_(num_records_per_group),
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current_group_(nullptr),
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num_records_in_current_group_(num_records_per_group) {
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}
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~IndexRecordList() {
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for (size_t i = 0; i < groups_.size(); i++) {
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delete[] groups_[i];
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}
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}
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void AddRecord(murmur_t hash, uint32_t offset) {
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if (num_records_in_current_group_ == num_records_per_group_) {
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current_group_ = AllocateNewGroup();
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num_records_in_current_group_ = 0;
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}
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auto& new_record = current_group_[num_records_in_current_group_];
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new_record.hash = hash;
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new_record.offset = offset;
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new_record.next = nullptr;
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num_records_in_current_group_++;
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}
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size_t GetNumRecords() {
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return (groups_.size() - 1) * num_records_per_group_
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+ num_records_in_current_group_;
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}
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IndexRecord* At(size_t index) {
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return &(groups_[index / num_records_per_group_]
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[index % num_records_per_group_]);
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}
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IndexRecord* AllocateNewGroup() {
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IndexRecord* result = new IndexRecord[num_records_per_group_];
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groups_.push_back(result);
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return result;
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}
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private:
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const size_t num_records_per_group_;
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IndexRecord* current_group_;
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// List of arrays allocated
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std::vector<IndexRecord*> groups_;
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size_t num_records_in_current_group_;
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};
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int PlainTableReader::PopulateIndexRecordList(
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IndexRecordList& record_list) {
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Slice key_slice;
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Slice key_prefix_slice;
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Slice key_suffix_slice;
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Slice value_slice;
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Slice prev_key_prefix_slice;
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uint32_t prev_key_prefix_hash = 0;
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uint32_t pos = data_start_offset_;
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int key_index_within_prefix = 0;
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bool first = true;
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std::string prefix_sub_index;
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HistogramImpl keys_per_prefix_hist;
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// Need map to be ordered to make sure sub indexes generated
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// are in order.
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int num_prefixes = 0;
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while (pos < data_end_offset_) {
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uint32_t key_offset = pos;
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status_ = Next(pos, &key_slice, &value_slice, pos);
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key_prefix_slice = GetPrefix(key_slice);
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if (first || prev_key_prefix_slice != key_prefix_slice) {
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num_prefixes++;
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if (!first) {
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keys_per_prefix_hist.Add(key_index_within_prefix);
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}
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key_index_within_prefix = 0;
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prev_key_prefix_slice = key_prefix_slice;
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prev_key_prefix_hash = GetSliceHash(key_prefix_slice);
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}
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if (key_index_within_prefix++ % 16 == 0) {
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// Add an index key for every 16 keys
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record_list.AddRecord(prev_key_prefix_hash, key_offset);
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}
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first = false;
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}
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keys_per_prefix_hist.Add(key_index_within_prefix);
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Log(options_.info_log, "Number of Keys per prefix Histogram: %s",
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keys_per_prefix_hist.ToString().c_str());
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return num_prefixes;
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}
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void PlainTableReader::Allocate(int num_prefixes) {
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if (hash_table_ != nullptr) {
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delete[] hash_table_;
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}
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if (bloom_bits_per_key_ > 0) {
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bloom_ = new DynamicBloom(num_prefixes * bloom_bits_per_key_);
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}
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double hash_table_size_multipier =
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(hash_table_ratio_ > 1.0) ? 1.0 : 1.0 / hash_table_ratio_;
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hash_table_size_ = num_prefixes * hash_table_size_multipier + 1;
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hash_table_ = new uint32_t[hash_table_size_];
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}
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size_t PlainTableReader::BucketizeIndexesAndFillBloom(
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IndexRecordList& record_list, int num_prefixes,
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std::vector<IndexRecord*>& hash2offsets,
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std::vector<uint32_t>& bucket_count) {
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size_t sub_index_size_needed = 0;
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bool first = true;
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uint32_t prev_hash = 0;
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size_t num_records = record_list.GetNumRecords();
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for (size_t i = 0; i < num_records; i++) {
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IndexRecord* index_record = record_list.At(i);
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uint32_t cur_hash = index_record->hash;
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if (first || prev_hash != cur_hash) {
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prev_hash = cur_hash;
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first = false;
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if (bloom_) {
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bloom_->AddHash(cur_hash);
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}
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}
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uint32_t bucket = getBucketIdFromHash(cur_hash, hash_table_size_);
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IndexRecord* prev_bucket_head = hash2offsets[bucket];
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index_record->next = prev_bucket_head;
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hash2offsets[bucket] = index_record;
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if (bucket_count[bucket] > 0) {
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if (bucket_count[bucket] == 1) {
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sub_index_size_needed += kOffsetLen + 1;
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}
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if (bucket_count[bucket] == 127) {
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// Need more than one byte for length
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sub_index_size_needed++;
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}
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sub_index_size_needed += kOffsetLen;
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}
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bucket_count[bucket]++;
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}
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return sub_index_size_needed;
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}
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void PlainTableReader::FillIndexes(size_t sub_index_size_needed,
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std::vector<IndexRecord*>& hash2offsets,
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std::vector<uint32_t>& bucket_count) {
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Log(options_.info_log, "Reserving %zu bytes for sub index",
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sub_index_size_needed);
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// 4 bytes buffer for variable length size
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size_t buffer_size = 64;
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size_t buffer_used = 0;
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sub_index_size_needed += buffer_size;
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sub_index_ = new char[sub_index_size_needed];
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size_t sub_index_offset = 0;
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char* prev_ptr;
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char* cur_ptr;
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uint32_t* sub_index_ptr;
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IndexRecord* record;
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for (int i = 0; i < hash_table_size_; i++) {
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uint32_t num_keys_for_bucket = bucket_count[i];
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switch (num_keys_for_bucket) {
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case 0:
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// No key for bucket
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hash_table_[i] = data_end_offset_;
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break;
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case 1:
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// point directly to the file offset
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hash_table_[i] = hash2offsets[i]->offset;
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break;
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default:
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// point to second level indexes.
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hash_table_[i] = sub_index_offset | kSubIndexMask;
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prev_ptr = sub_index_ + sub_index_offset;
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cur_ptr = EncodeVarint32(prev_ptr, num_keys_for_bucket);
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sub_index_offset += cur_ptr - prev_ptr;
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if (cur_ptr - prev_ptr > 2
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|| (cur_ptr - prev_ptr == 2 && num_keys_for_bucket <= 127)) {
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// Need to resize sub_index. Exponentially grow buffer.
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buffer_used += cur_ptr - prev_ptr - 1;
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if (buffer_used + 4 > buffer_size) {
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Log(options_.info_log, "Recalculate suffix_map length to %zu",
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sub_index_size_needed);
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sub_index_size_needed += buffer_size;
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buffer_size *= 2;
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char* new_sub_index = new char[sub_index_size_needed];
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memcpy(new_sub_index, sub_index_, sub_index_offset);
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delete[] sub_index_;
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sub_index_ = new_sub_index;
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}
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}
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sub_index_ptr = (uint32_t*) (sub_index_ + sub_index_offset);
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record = hash2offsets[i];
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int j;
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for (j = num_keys_for_bucket - 1;
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j >= 0 && record; j--, record = record->next) {
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sub_index_ptr[j] = record->offset;
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}
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assert(j == -1 && record == nullptr);
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sub_index_offset += kOffsetLen * num_keys_for_bucket;
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break;
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}
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}
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Log(options_.info_log, "hash table size: %d, suffix_map length %zu",
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hash_table_size_, sub_index_size_needed);
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}
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// PopulateIndex() builds index of keys.
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// hash_table_ contains buckets size of hash_table_size_, each is a 32-bit
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// integer. The lower 31 bits contain an offset value (explained below) and
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// the first bit of the integer indicates type of the offset:
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//
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// 0 indicates that the bucket contains only one prefix (no conflict when
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// hashing this prefix), whose first row starts from this offset of the file.
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// 1 indicates that the bucket contains more than one prefixes, or there
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// are too many rows for one prefix so we need a binary search for it. In
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// this case, the offset indicates the offset of sub_index_ holding the
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// binary search indexes of keys for those rows. Those binary search indexes
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// are organized in this way:
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//
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// The first 4 bytes, indicates how many indexes (N) are stored after it. After
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// it, there are N 32-bit integers, each points of an offset of the file, which
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// points to starting of a row. Those offsets need to be guaranteed to be in
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// ascending order so the keys they are pointing to are also in ascending order
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// to make sure we can use them to do binary searches.
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Status PlainTableReader::PopulateIndex() {
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// Get mmapped memory to file_data_.
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Status s = file_->Read(0, file_size_, &file_data_, nullptr);
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if (!s.ok()) {
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return s;
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}
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IndexRecordList record_list(256);
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// First, read the whole file, for every 16 rows for a prefix (starting from
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// the first one), generate a record of (hash, offset) and append it to
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// IndexRecordList, which is a data structure created to store them.
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int num_prefixes = PopulateIndexRecordList(record_list);
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// Calculated hash table and bloom filter size and allocate memory for indexes
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// and bloom filter based on the number of prefixes.
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Allocate(num_prefixes);
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// Bucketize all the index records to a temp data structure, in which for
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// each bucket, we generate a linked list of IndexRecord, in reversed order.
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std::vector<IndexRecord*> hash2offsets(hash_table_size_, nullptr);
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std::vector<uint32_t> bucket_count(hash_table_size_, 0);
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size_t sub_index_size_needed = BucketizeIndexesAndFillBloom(record_list,
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num_prefixes,
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hash2offsets,
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bucket_count);
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// From the temp data structure, populate indexes.
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FillIndexes(sub_index_size_needed, hash2offsets, bucket_count);
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return Status::OK();
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}
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Status PlainTableReader::GetOffset(const Slice& target, const Slice& prefix,
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uint32_t prefix_hash, bool& prefix_matched,
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uint32_t& ret_offset) {
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prefix_matched = false;
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int bucket = getBucketIdFromHash(prefix_hash, hash_table_size_);
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uint32_t bucket_value = hash_table_[bucket];
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if (bucket_value == data_end_offset_) {
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ret_offset = data_end_offset_;
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return Status::OK();
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} else if ((bucket_value & kSubIndexMask) == 0) {
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// point directly to the file
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ret_offset = bucket_value;
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return Status::OK();
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}
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// point to sub-index, need to do a binary search
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uint32_t low = 0;
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uint64_t prefix_index_offset = bucket_value ^ kSubIndexMask;
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const char* index_ptr = sub_index_ + prefix_index_offset;
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uint32_t upper_bound;
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const uint32_t* base_ptr = (const uint32_t*) GetVarint32Ptr(index_ptr,
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index_ptr + 4,
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&upper_bound);
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uint32_t high = upper_bound;
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Slice mid_key;
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// The key is between [low, high). Do a binary search between it.
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while (high - low > 1) {
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uint32_t mid = (high + low) / 2;
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uint32_t file_offset = base_ptr[mid];
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size_t tmp;
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Status s = ReadKey(file_data_.data() + file_offset, &mid_key, tmp);
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if (!s.ok()) {
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return s;
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}
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int cmp_result = options_.comparator->Compare(target, mid_key);
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if (cmp_result > 0) {
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low = mid;
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} else {
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if (cmp_result == 0) {
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// Happen to have found the exact key or target is smaller than the
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// first key after base_offset.
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prefix_matched = true;
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ret_offset = file_offset;
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return Status::OK();
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} else {
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high = mid;
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}
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}
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}
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// Both of the key at the position low or low+1 could share the same
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// prefix as target. We need to rule out one of them to avoid to go
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// to the wrong prefix.
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Slice low_key;
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size_t tmp;
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uint32_t low_key_offset = base_ptr[low];
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Status s = ReadKey(file_data_.data() + low_key_offset, &low_key, tmp);
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if (GetPrefix(low_key) == prefix) {
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prefix_matched = true;
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ret_offset = low_key_offset;
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} else if (low + 1 < upper_bound) {
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// There is possible a next prefix, return it
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prefix_matched = false;
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ret_offset = base_ptr[low + 1];
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} else {
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// target is larger than a key of the last prefix in this bucket
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// but with a different prefix. Key does not exist.
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ret_offset = data_end_offset_;
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}
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return Status::OK();
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}
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bool PlainTableReader::MayHavePrefix(uint32_t hash) {
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return bloom_ == nullptr || bloom_->MayContainHash(hash);
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}
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Status PlainTableReader::ReadKey(const char* row_ptr, Slice* key,
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size_t& bytes_read) {
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const char* key_ptr;
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bytes_read = 0;
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size_t internal_key_size;
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if (IsFixedLength()) {
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internal_key_size = GetFixedInternalKeyLength();
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key_ptr = row_ptr;
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} else {
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uint32_t key_size;
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key_ptr = GetVarint32Ptr(row_ptr, file_data_.data() + data_end_offset_,
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&key_size);
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internal_key_size = (size_t) key_size;
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bytes_read = key_ptr - row_ptr;
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}
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if (row_ptr + internal_key_size >= file_data_.data() + data_end_offset_) {
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return Status::Corruption("Unable to read the next key");
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}
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*key = Slice(key_ptr, internal_key_size);
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bytes_read += internal_key_size;
|
|
return Status::OK();
|
|
}
|
|
|
|
Status PlainTableReader::Next(uint32_t offset, Slice* key, Slice* value,
|
|
uint32_t& next_offset) {
|
|
if (offset == data_end_offset_) {
|
|
next_offset = data_end_offset_;
|
|
return Status::OK();
|
|
}
|
|
|
|
if (offset > data_end_offset_) {
|
|
return Status::Corruption("Offset is out of file size");
|
|
}
|
|
|
|
const char* row_ptr = file_data_.data() + offset;
|
|
size_t bytes_for_key;
|
|
Status s = ReadKey(row_ptr, key, bytes_for_key);
|
|
uint32_t value_size;
|
|
const char* value_ptr = GetVarint32Ptr(row_ptr + bytes_for_key,
|
|
file_data_.data() + data_end_offset_,
|
|
&value_size);
|
|
if (value_ptr == nullptr) {
|
|
return Status::Corruption("Error reading value length.");
|
|
}
|
|
next_offset = offset + (value_ptr - row_ptr) + value_size;
|
|
if (next_offset > data_end_offset_) {
|
|
return Status::Corruption("Reach end of file when reading value");
|
|
}
|
|
*value = Slice(value_ptr, value_size);
|
|
|
|
return Status::OK();
|
|
}
|
|
|
|
Status PlainTableReader::Get(
|
|
const ReadOptions& ro, const Slice& target, void* arg,
|
|
bool (*saver)(void*, const Slice&, const Slice&, bool),
|
|
void (*mark_key_may_exist)(void*)) {
|
|
// Check bloom filter first.
|
|
Slice prefix_slice = GetPrefix(target);
|
|
uint32_t prefix_hash = GetSliceHash(prefix_slice);
|
|
if (!MayHavePrefix(prefix_hash)) {
|
|
return Status::OK();
|
|
}
|
|
uint32_t offset;
|
|
bool prefix_match;
|
|
Status s = GetOffset(target, prefix_slice, prefix_hash, prefix_match, offset);
|
|
if (!s.ok()) {
|
|
return s;
|
|
}
|
|
Slice found_key;
|
|
Slice found_value;
|
|
while (offset < data_end_offset_) {
|
|
Status s = Next(offset, &found_key, &found_value, offset);
|
|
if (!s.ok()) {
|
|
return s;
|
|
}
|
|
if (!prefix_match) {
|
|
// Need to verify prefix for the first key found if it is not yet
|
|
// checked.
|
|
if (GetPrefix(found_key) != prefix_slice) {
|
|
return Status::OK();
|
|
}
|
|
prefix_match = true;
|
|
}
|
|
if (options_.comparator->Compare(found_key, target) >= 0
|
|
&& !(*saver)(arg, found_key, found_value, true)) {
|
|
break;
|
|
}
|
|
}
|
|
return Status::OK();
|
|
}
|
|
|
|
bool PlainTableReader::TEST_KeyInCache(const ReadOptions& options,
|
|
const Slice& key) {
|
|
return false;
|
|
}
|
|
|
|
uint64_t PlainTableReader::ApproximateOffsetOf(const Slice& key) {
|
|
return 0;
|
|
}
|
|
|
|
PlainTableIterator::PlainTableIterator(PlainTableReader* table) :
|
|
table_(table) {
|
|
next_offset_ = offset_ = table_->data_end_offset_;
|
|
}
|
|
|
|
PlainTableIterator::~PlainTableIterator() {
|
|
}
|
|
|
|
bool PlainTableIterator::Valid() const {
|
|
return offset_ < table_->data_end_offset_
|
|
&& offset_ >= table_->data_start_offset_;
|
|
}
|
|
|
|
void PlainTableIterator::SeekToFirst() {
|
|
next_offset_ = table_->data_start_offset_;
|
|
if (next_offset_ >= table_->data_end_offset_) {
|
|
next_offset_ = offset_ = table_->data_end_offset_;
|
|
} else {
|
|
Next();
|
|
}
|
|
}
|
|
|
|
void PlainTableIterator::SeekToLast() {
|
|
assert(false);
|
|
}
|
|
|
|
void PlainTableIterator::Seek(const Slice& target) {
|
|
Slice prefix_slice = table_->GetPrefix(target);
|
|
uint32_t prefix_hash = GetSliceHash(prefix_slice);
|
|
if (!table_->MayHavePrefix(prefix_hash)) {
|
|
offset_ = next_offset_ = table_->data_end_offset_;
|
|
return;
|
|
}
|
|
bool prefix_match;
|
|
status_ = table_->GetOffset(target, prefix_slice, prefix_hash, prefix_match,
|
|
next_offset_);
|
|
if (!status_.ok()) {
|
|
offset_ = next_offset_ = table_->data_end_offset_;
|
|
return;
|
|
}
|
|
|
|
if (next_offset_ < table_-> data_end_offset_) {
|
|
for (Next(); status_.ok() && Valid(); Next()) {
|
|
if (!prefix_match) {
|
|
// Need to verify the first key's prefix
|
|
if (table_->GetPrefix(key()) != prefix_slice) {
|
|
offset_ = next_offset_ = table_->data_end_offset_;
|
|
break;
|
|
}
|
|
prefix_match = true;
|
|
}
|
|
if (table_->options_.comparator->Compare(key(), target) >= 0) {
|
|
break;
|
|
}
|
|
}
|
|
} else {
|
|
offset_ = table_->data_end_offset_;
|
|
}
|
|
}
|
|
|
|
void PlainTableIterator::Next() {
|
|
offset_ = next_offset_;
|
|
Slice tmp_slice;
|
|
status_ = table_->Next(next_offset_, &key_, &value_, next_offset_);
|
|
}
|
|
|
|
void PlainTableIterator::Prev() {
|
|
assert(false);
|
|
}
|
|
|
|
Slice PlainTableIterator::key() const {
|
|
return key_;
|
|
}
|
|
|
|
Slice PlainTableIterator::value() const {
|
|
return value_;
|
|
}
|
|
|
|
Status PlainTableIterator::status() const {
|
|
return status_;
|
|
}
|
|
|
|
} // namespace rocksdb
|