145 lines
5.1 KiB
C++
145 lines
5.1 KiB
C++
// Copyright (c) 2014, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// 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 <stddef.h>
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namespace rocksdb {
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class Cache;
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class Comparator;
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class Env;
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class FilterPolicy;
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class Logger;
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struct Options;
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class Snapshot;
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enum CompressionType : char;
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// Options to control the behavior of a database (passed to
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// DB::Open). A LevelDBOptions object can be initialized as though
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// it were a LevelDB Options object, and then it can be converted into
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// a RocksDB Options object.
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struct LevelDBOptions {
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// -------------------
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// Parameters that affect behavior
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// Comparator used to define the order of keys in the table.
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// Default: a comparator that uses lexicographic byte-wise ordering
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//
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// REQUIRES: The client must ensure that the comparator supplied
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// here has the same name and orders keys *exactly* the same as the
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// comparator provided to previous open calls on the same DB.
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const Comparator* comparator;
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// If true, the database will be created if it is missing.
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// Default: false
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bool create_if_missing;
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// If true, an error is raised if the database already exists.
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// Default: false
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bool error_if_exists;
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// If true, the implementation will do aggressive checking of the
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// data it is processing and will stop early if it detects any
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// errors. This may have unforeseen ramifications: for example, a
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// corruption of one DB entry may cause a large number of entries to
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// become unreadable or for the entire DB to become unopenable.
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// Default: false
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bool paranoid_checks;
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// Use the specified object to interact with the environment,
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// e.g. to read/write files, schedule background work, etc.
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// Default: Env::Default()
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Env* env;
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// Any internal progress/error information generated by the db will
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// be written to info_log if it is non-NULL, or to a file stored
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// in the same directory as the DB contents if info_log is NULL.
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// Default: NULL
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Logger* info_log;
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// -------------------
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// Parameters that affect performance
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// Amount of data to build up in memory (backed by an unsorted log
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// on disk) before converting to a sorted on-disk file.
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//
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// Larger values increase performance, especially during bulk loads.
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// Up to two write buffers may be held in memory at the same time,
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// so you may wish to adjust this parameter to control memory usage.
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// Also, a larger write buffer will result in a longer recovery time
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// the next time the database is opened.
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//
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// Default: 4MB
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size_t write_buffer_size;
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// Number of open files that can be used by the DB. You may need to
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// increase this if your database has a large working set (budget
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// one open file per 2MB of working set).
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//
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// Default: 1000
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int max_open_files;
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// Control over blocks (user data is stored in a set of blocks, and
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// a block is the unit of reading from disk).
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// If non-NULL, use the specified cache for blocks.
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// If NULL, leveldb will automatically create and use an 8MB internal cache.
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// Default: NULL
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Cache* block_cache;
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// Approximate size of user data packed per block. Note that the
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// block size specified here corresponds to uncompressed data. The
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// actual size of the unit read from disk may be smaller if
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// compression is enabled. This parameter can be changed dynamically.
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//
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// Default: 4K
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size_t block_size;
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// Number of keys between restart points for delta encoding of keys.
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// This parameter can be changed dynamically. Most clients should
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// leave this parameter alone.
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//
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// Default: 16
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int block_restart_interval;
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// Compress blocks using the specified compression algorithm. This
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// parameter can be changed dynamically.
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//
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// Default: kSnappyCompression, which gives lightweight but fast
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// compression.
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//
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// Typical speeds of kSnappyCompression on an Intel(R) Core(TM)2 2.4GHz:
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// ~200-500MB/s compression
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// ~400-800MB/s decompression
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// Note that these speeds are significantly faster than most
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// persistent storage speeds, and therefore it is typically never
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// worth switching to kNoCompression. Even if the input data is
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// incompressible, the kSnappyCompression implementation will
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// efficiently detect that and will switch to uncompressed mode.
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CompressionType compression;
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// If non-NULL, use the specified filter policy to reduce disk reads.
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// Many applications will benefit from passing the result of
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// NewBloomFilterPolicy() here.
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//
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// Default: NULL
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const FilterPolicy* filter_policy;
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// Create a LevelDBOptions object with default values for all fields.
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LevelDBOptions();
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};
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// Converts a LevelDBOptions object into a RocksDB Options object.
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Options ConvertOptions(const LevelDBOptions& leveldb_options);
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} // namespace rocksdb
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