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