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rocksdb/table/plain_table_reader.h

183 lines
5.8 KiB

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include <unordered_map>
#include <memory>
#include <stdint.h>
#include "rocksdb/env.h"
#include "rocksdb/iterator.h"
#include "rocksdb/table.h"
namespace rocksdb {
class Block;
class BlockHandle;
class Footer;
struct Options;
class RandomAccessFile;
struct ReadOptions;
class TableCache;
class TableReader;
using std::unique_ptr;
using std::unordered_map;
// Based on following output file format:
// +-------------+
// | version |
// +-------------+------------------------------+ <= key1_data_offset
// | key1 | value_size (4 bytes) | |
// +----------------------------------------+ |
// | value1 |
// | |
// +----------------------------------------+---+ <= key2_data_offset
// | key2 | value_size (4 bytes) | |
// +----------------------------------------+ |
// | value2 |
// | |
// | ...... |
// +-----------------+--------------------------+ <= index_block_offset
// | key1 | key1 offset (8 bytes) |
// +-----------------+--------------------------+ <= key2_index_offset
// | key2 | key2 offset (8 bytes) |
// +-----------------+--------------------------+ <= key3_index_offset
// | key3 | key3 offset (8 bytes) |
// +-----------------+--------------------------+ <= key4_index_offset
// | ...... |
// +-----------------+------------+-------------+
// When opening the output file, IndexedTableReader creates a hash table
// from key prefixes to offset of the output file. IndexedTable will decide
// whether it points to the data offset of the first key with the key prefix
// or the offset of it. If there are too many keys share this prefix, it will
// create a binary search-able index from the suffix to offset on disk.
//
// The implementation of IndexedTableReader requires output file is mmaped
class PlainTableReader: public TableReader {
public:
static Status Open(const Options& options, const EnvOptions& soptions,
unique_ptr<RandomAccessFile> && file, uint64_t file_size,
unique_ptr<TableReader>* table, const int user_key_size,
const int key_prefix_len, const int bloom_num_bits,
double hash_table_ratio);
bool PrefixMayMatch(const Slice& internal_prefix);
Iterator* NewIterator(const ReadOptions&);
Status Get(
const ReadOptions&, const Slice& key, void* arg,
bool (*handle_result)(void* arg, const Slice& k, const Slice& v, bool),
void (*mark_key_may_exist)(void*) = nullptr);
uint64_t ApproximateOffsetOf(const Slice& key);
bool TEST_KeyInCache(const ReadOptions& options, const Slice& key);
void SetupForCompaction();
TableProperties& GetTableProperties() {
return tbl_props;
}
PlainTableReader(const EnvOptions& storage_options, uint64_t file_size,
int user_key_size, int key_prefix_len, int bloom_num_bits,
double hash_table_ratio);
~PlainTableReader();
private:
uint32_t* hash_table_;
int hash_table_size_;
std::string sub_index_;
Options options_;
const EnvOptions& soptions_;
Status status_;
unique_ptr<RandomAccessFile> file_;
Slice file_data_;
uint32_t version_;
uint32_t file_size_;
uint32_t data_start_offset_;
uint32_t data_end_offset_;
const size_t user_key_size_;
const size_t key_prefix_len_;
const double hash_table_ratio_;
const FilterPolicy* filter_policy_;
std::string filter_str_;
Slice filter_slice_;
TableProperties tbl_props;
static const size_t kNumInternalBytes = 8;
static const uint32_t kSubIndexMask = 0x80000000;
static const size_t kOffsetLen = sizeof(uint32_t);
inline size_t GetInternalKeyLength() {
return user_key_size_ + kNumInternalBytes;
}
friend class TableCache;
friend class PlainTableIterator;
// Populate the internal indexes. It must be called before
// any query to the table.
// This query will populate the hash table hash_table_, the second
// level of indexes sub_index_ and bloom filter filter_slice_ if enabled.
Status PopulateIndex(uint64_t file_size);
// Check bloom filter to see whether it might contain this prefix
bool MayHavePrefix(const Slice& target_prefix);
// Read the key and value at offset to key and value.
// tmp_slice is a tmp slice.
// return next_offset as the offset for the next key.
Status Next(uint32_t offset, Slice* key, Slice* value, uint32_t& next_offset);
// Get file offset for key target.
// return value prefix_matched is set to true if the offset is confirmed
// for a key with the same prefix as target.
uint32_t GetOffset(const Slice& target, bool& prefix_matched);
// No copying allowed
explicit PlainTableReader(const TableReader&) = delete;
void operator=(const TableReader&) = delete;
};
// Iterator to iterate IndexedTable
class PlainTableIterator: public Iterator {
public:
explicit PlainTableIterator(PlainTableReader* table);
~PlainTableIterator();
bool Valid() const;
void SeekToFirst();
void SeekToLast();
void Seek(const Slice& target);
void Next();
void Prev();
Slice key() const;
Slice value() const;
Status status() const;
private:
PlainTableReader* table_;
uint32_t offset_;
uint32_t next_offset_;
Slice key_;
Slice value_;
Status status_;
// No copying allowed
PlainTableIterator(const PlainTableIterator&) = delete;
void operator=(const Iterator&) = delete;
};
} // namespace rocksdb