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f040e536e4
Summary: PlainTableReader to use a more customized hash table. This patch assumes the SST file is smaller than 2GB: (1) Every bucket uses 32-bit integer (2) no key is stored in bucket (3) use the first bit of the bucket value to distinguish it points to the file offset or a second level index. This index schema fits the use case that most of prefixes have very small number of keys Test Plan: plain_table_db_test Reviewers: haobo, kailiu, dhruba Reviewed By: haobo CC: nkg-, leveldb Differential Revision: https://reviews.facebook.net/D14343
81 lines
3.0 KiB
C++
81 lines
3.0 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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#pragma once
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#include <memory>
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#include <stdint.h>
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#include "rocksdb/options.h"
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#include "rocksdb/table.h"
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namespace rocksdb {
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struct Options;
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struct EnvOptions;
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using std::unique_ptr;
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class Status;
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class RandomAccessFile;
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class WritableFile;
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class Table;
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class TableBuilder;
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// IndexedTable requires fixed length key, configured as a constructor
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// parameter of the factory class. Output file format:
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// +-------------+
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// | version |
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// +-------------+------------------------------+ <= key1 offset
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// | key1 | value_size (4 bytes) | |
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// +----------------------------------------+ |
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// | value1 |
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// | |
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// +----------------------------------------+---+ <= key2 offset
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// | key2 | value_size (4 bytes) | |
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// +----------------------------------------+ |
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// | value2 |
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// | |
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// | ...... |
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// +-----------------+--------------------------+ <= index_block_offset
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// | key1 | key1 offset (8 bytes) |
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// +-----------------+--------------------------+
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// | key2 | key2 offset (8 bytes) |
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// +-----------------+--------------------------+
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// | key3 | key3 offset (8 bytes) |
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// +-----------------+--------------------------+
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// | ...... |
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// +-----------------+------------+-------------+
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class PlainTableFactory: public TableFactory {
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public:
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~PlainTableFactory() {
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}
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// user_key_size is the length of the user key. key_prefix_len is the
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// length of the prefix used for in-memory indexes. bloom_num_bits is
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// number of bits used for bloom filer per key. hash_table_ratio is
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// the desired ultilization of the hash table used for prefix hashing.
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// hash_table_ratio = number of prefixes / #buckets in the hash table
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PlainTableFactory(int user_key_size, int key_prefix_len,
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int bloom_num_bits = 0, double hash_table_ratio = 0.75) :
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user_key_size_(user_key_size), key_prefix_len_(key_prefix_len),
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bloom_num_bits_(bloom_num_bits), hash_table_ratio_(hash_table_ratio) {
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}
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const char* Name() const override {
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return "PlainTable";
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}
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Status GetTableReader(const Options& options, 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) const override;
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TableBuilder* GetTableBuilder(const Options& options, WritableFile* file,
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CompressionType compression_type) const
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override;
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private:
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int user_key_size_;
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int key_prefix_len_;
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int bloom_num_bits_;
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double hash_table_ratio_;
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};
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} // namespace rocksdb
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