Struct rocksdb::Options

pub struct Options { /* private fields */ }

Database-wide options around performance and behavior.

Please read the official tuning guide and most importantly, measure performance under realistic workloads with realistic hardware.

Examples

use rocksdb::{Options, DB};
use rocksdb::DBCompactionStyle;

fn badly_tuned_for_somebody_elses_disk() -> DB {
   let path = "path/for/rocksdb/storageX";
   let mut opts = Options::default();
   opts.create_if_missing(true);
   opts.set_max_open_files(10000);
   opts.set_use_fsync(false);
   opts.set_bytes_per_sync(8388608);
   opts.optimize_for_point_lookup(1024);
   opts.set_table_cache_num_shard_bits(6);
   opts.set_max_write_buffer_number(32);
   opts.set_write_buffer_size(536870912);
   opts.set_target_file_size_base(1073741824);
   opts.set_min_write_buffer_number_to_merge(4);
   opts.set_level_zero_stop_writes_trigger(2000);
   opts.set_level_zero_slowdown_writes_trigger(0);
   opts.set_compaction_style(DBCompactionStyle::Universal);
   opts.set_disable_auto_compactions(true);

   DB::open(&opts, path).unwrap()
}

Implementations

impl Options

pub fn load_latest<P: AsRef<Path>>( path: P, env: Env, ignore_unknown_options: bool, cache: Cache, ) -> Result<(Options, Vec<ColumnFamilyDescriptor>), Error>

Constructs the DBOptions and ColumnFamilyDescriptors by loading the latest RocksDB options file stored in the specified rocksdb database.

pub fn increase_parallelism(&mut self, parallelism: i32)

By default, RocksDB uses only one background thread for flush and compaction. Calling this function will set it up such that total of total_threads is used. Good value for total_threads is the number of cores. You almost definitely want to call this function if your system is bottlenecked by RocksDB.

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.increase_parallelism(3);

pub fn optimize_level_style_compaction(&mut self, memtable_memory_budget: usize)

Optimize level style compaction.

Default values for some parameters in Options are not optimized for heavy workloads and big datasets, which means you might observe write stalls under some conditions.

This can be used as one of the starting points for tuning RocksDB options in such cases.

Internally, it sets write_buffer_size, min_write_buffer_number_to_merge, max_write_buffer_number, level0_file_num_compaction_trigger, target_file_size_base, max_bytes_for_level_base, so it can override if those parameters were set before.

It sets buffer sizes so that memory consumption would be constrained by memtable_memory_budget.

pub fn optimize_universal_style_compaction( &mut self, memtable_memory_budget: usize, )

Optimize universal style compaction.

Default values for some parameters in Options are not optimized for heavy workloads and big datasets, which means you might observe write stalls under some conditions.

This can be used as one of the starting points for tuning RocksDB options in such cases.

Internally, it sets write_buffer_size, min_write_buffer_number_to_merge, max_write_buffer_number, level0_file_num_compaction_trigger, target_file_size_base, max_bytes_for_level_base, so it can override if those parameters were set before.

It sets buffer sizes so that memory consumption would be constrained by memtable_memory_budget.

pub fn create_if_missing(&mut self, create_if_missing: bool)

If true, the database will be created if it is missing.

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.create_if_missing(true);

pub fn create_missing_column_families(&mut self, create_missing_cfs: bool)

If true, any column families that didn’t exist when opening the database will be created.

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.create_missing_column_families(true);

pub fn set_error_if_exists(&mut self, enabled: bool)

Specifies whether an error should be raised if the database already exists.

Default: false

pub fn set_paranoid_checks(&mut self, enabled: bool)

Enable/disable paranoid checks.

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. If any of the writes to the database fails (Put, Delete, Merge, Write), the database will switch to read-only mode and fail all other Write operations.

Default: false

pub fn set_db_paths(&mut self, paths: &[DBPath])

A list of paths where SST files can be put into, with its target size. Newer data is placed into paths specified earlier in the vector while older data gradually moves to paths specified later in the vector.

For example, you have a flash device with 10GB allocated for the DB, as well as a hard drive of 2TB, you should config it to be: [{“/flash_path”, 10GB}, {“/hard_drive”, 2TB}]

The system will try to guarantee data under each path is close to but not larger than the target size. But current and future file sizes used by determining where to place a file are based on best-effort estimation, which means there is a chance that the actual size under the directory is slightly more than target size under some workloads. User should give some buffer room for those cases.

If none of the paths has sufficient room to place a file, the file will be placed to the last path anyway, despite to the target size.

Placing newer data to earlier paths is also best-efforts. User should expect user files to be placed in higher levels in some extreme cases.

If left empty, only one path will be used, which is path passed when opening the DB.

Default: empty

pub fn set_env(&mut self, env: &Env)

Use the specified object to interact with the environment, e.g. to read/write files, schedule background work, etc. In the near future, support for doing storage operations such as read/write files through env will be deprecated in favor of file_system.

Default: Env::default()

pub fn set_compression_type(&mut self, t: DBCompressionType)

Sets the compression algorithm that will be used for compressing blocks.

Default: DBCompressionType::Snappy (DBCompressionType::None if snappy feature is not enabled).

Examples

use rocksdb::{Options, DBCompressionType};

let mut opts = Options::default();
opts.set_compression_type(DBCompressionType::Snappy);

pub fn set_bottommost_compression_type(&mut self, t: DBCompressionType)

Sets the bottom-most compression algorithm that will be used for compressing blocks at the bottom-most level.

Note that to actually unable bottom-most compression configuration after setting the compression type it needs to be enabled by calling set_bottommost_compression_options or set_bottommost_zstd_max_train_bytes method with enabled argument set to true.

Examples

use rocksdb::{Options, DBCompressionType};

let mut opts = Options::default();
opts.set_bottommost_compression_type(DBCompressionType::Zstd);
opts.set_bottommost_zstd_max_train_bytes(0, true);

pub fn set_compression_per_level(&mut self, level_types: &[DBCompressionType])

Different levels can have different compression policies. There are cases where most lower levels would like to use quick compression algorithms while the higher levels (which have more data) use compression algorithms that have better compression but could be slower. This array, if non-empty, should have an entry for each level of the database; these override the value specified in the previous field ‘compression’.

Examples

use rocksdb::{Options, DBCompressionType};

let mut opts = Options::default();
opts.set_compression_per_level(&[
    DBCompressionType::None,
    DBCompressionType::None,
    DBCompressionType::Snappy,
    DBCompressionType::Snappy,
    DBCompressionType::Snappy
]);

pub fn set_compression_options( &mut self, w_bits: c_int, level: c_int, strategy: c_int, max_dict_bytes: c_int, )

Maximum size of dictionaries used to prime the compression library. Enabling dictionary can improve compression ratios when there are repetitions across data blocks.

The dictionary is created by sampling the SST file data. If zstd_max_train_bytes is nonzero, the samples are passed through zstd’s dictionary generator. Otherwise, the random samples are used directly as the dictionary.

When compression dictionary is disabled, we compress and write each block before buffering data for the next one. When compression dictionary is enabled, we buffer all SST file data in-memory so we can sample it, as data can only be compressed and written after the dictionary has been finalized. So users of this feature may see increased memory usage.

Default: 0

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_compression_options(4, 5, 6, 7);

pub fn set_bottommost_compression_options( &mut self, w_bits: c_int, level: c_int, strategy: c_int, max_dict_bytes: c_int, enabled: bool, )

Sets compression options for blocks at the bottom-most level. Meaning of all settings is the same as in set_compression_options method but affect only the bottom-most compression which is set using set_bottommost_compression_type method.

Examples

use rocksdb::{Options, DBCompressionType};

let mut opts = Options::default();
opts.set_bottommost_compression_type(DBCompressionType::Zstd);
opts.set_bottommost_compression_options(4, 5, 6, 7, true);

pub fn set_zstd_max_train_bytes(&mut self, value: c_int)

Sets maximum size of training data passed to zstd’s dictionary trainer. Using zstd’s dictionary trainer can achieve even better compression ratio improvements than using max_dict_bytes alone.

The training data will be used to generate a dictionary of max_dict_bytes.

Default: 0.

pub fn set_bottommost_zstd_max_train_bytes( &mut self, value: c_int, enabled: bool, )

Sets maximum size of training data passed to zstd’s dictionary trainer when compressing the bottom-most level. Using zstd’s dictionary trainer can achieve even better compression ratio improvements than using max_dict_bytes alone.

The training data will be used to generate a dictionary of max_dict_bytes.

Default: 0.

pub fn set_compaction_readahead_size( &mut self, compaction_readahead_size: usize, )

If non-zero, we perform bigger reads when doing compaction. If you’re running RocksDB on spinning disks, you should set this to at least 2MB. That way RocksDB’s compaction is doing sequential instead of random reads.

When non-zero, we also force new_table_reader_for_compaction_inputs to true.

Default: 0

pub fn set_level_compaction_dynamic_level_bytes(&mut self, v: bool)

Allow RocksDB to pick dynamic base of bytes for levels. With this feature turned on, RocksDB will automatically adjust max bytes for each level. The goal of this feature is to have lower bound on size amplification.

Default: false.

pub fn set_merge_operator_associative<F: MergeFn + Clone>( &mut self, name: impl CStrLike, full_merge_fn: F, )

pub fn set_merge_operator<F: MergeFn, PF: MergeFn>( &mut self, name: impl CStrLike, full_merge_fn: F, partial_merge_fn: PF, )

pub fn add_merge_operator<F: MergeFn + Clone>( &mut self, name: &str, merge_fn: F, )

👎Deprecated since 0.5.0: add_merge_operator has been renamed to set_merge_operator

pub fn set_compaction_filter<F>(&mut self, name: impl CStrLike, filter_fn: F)

where F: CompactionFilterFn + Send + 'static,

Sets a compaction filter used to determine if entries should be kept, changed, or removed during compaction.

An example use case is to remove entries with an expired TTL.

If you take a snapshot of the database, only values written since the last snapshot will be passed through the compaction filter.

If multi-threaded compaction is used, filter_fn may be called multiple times simultaneously.

pub fn set_compaction_filter_factory<F>(&mut self, factory: F)

where F: CompactionFilterFactory + 'static,

This is a factory that provides compaction filter objects which allow an application to modify/delete a key-value during background compaction.

A new filter will be created on each compaction run. If multithreaded compaction is being used, each created CompactionFilter will only be used from a single thread and so does not need to be thread-safe.

Default: nullptr

pub fn set_comparator( &mut self, name: impl CStrLike, compare_fn: Box<dyn Fn(&[u8], &[u8]) -> Ordering>, )

Sets the comparator used to define the order of keys in the table. Default: a comparator that uses lexicographic byte-wise ordering

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.

pub fn set_prefix_extractor(&mut self, prefix_extractor: SliceTransform)

pub fn optimize_for_point_lookup(&mut self, cache_size: u64)

pub fn set_optimize_filters_for_hits(&mut self, optimize_for_hits: bool)

Sets the optimize_filters_for_hits flag

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_optimize_filters_for_hits(true);

pub fn set_delete_obsolete_files_period_micros(&mut self, micros: u64)

Sets the periodicity when obsolete files get deleted.

The files that get out of scope by compaction process will still get automatically delete on every compaction, regardless of this setting.

Default: 6 hours

pub fn prepare_for_bulk_load(&mut self)

Prepare the DB for bulk loading.

All data will be in level 0 without any automatic compaction. It’s recommended to manually call CompactRange(NULL, NULL) before reading from the database, because otherwise the read can be very slow.

pub fn set_max_open_files(&mut self, nfiles: c_int)

Sets the 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. Value -1 means files opened are always kept open. You can estimate number of files based on target_file_size_base and target_file_size_multiplier for level-based compaction. For universal-style compaction, you can usually set it to -1.

Default: -1

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_max_open_files(10);

pub fn set_max_file_opening_threads(&mut self, nthreads: c_int)

If max_open_files is -1, DB will open all files on DB::Open(). You can use this option to increase the number of threads used to open the files. Default: 16

pub fn set_use_fsync(&mut self, useit: bool)

By default, writes to stable storage use fdatasync (on platforms where this function is available). If this option is true, fsync is used instead.

fsync and fdatasync are equally safe for our purposes and fdatasync is faster, so it is rarely necessary to set this option. It is provided as a workaround for kernel/filesystem bugs, such as one that affected fdatasync with ext4 in kernel versions prior to 3.7.

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_use_fsync(true);

pub fn set_db_log_dir<P: AsRef<Path>>(&mut self, path: P)

Specifies the absolute info LOG dir.

If it is empty, the log files will be in the same dir as data. If it is non empty, the log files will be in the specified dir, and the db data dir’s absolute path will be used as the log file name’s prefix.

Default: empty

pub fn set_log_level(&mut self, level: LogLevel)

Specifies the log level. Consider the LogLevel enum for a list of possible levels.

Default: Info

Examples

use rocksdb::{Options, LogLevel};

let mut opts = Options::default();
opts.set_log_level(LogLevel::Warn);

pub fn set_bytes_per_sync(&mut self, nbytes: u64)

Allows OS to incrementally sync files to disk while they are being written, asynchronously, in the background. This operation can be used to smooth out write I/Os over time. Users shouldn’t rely on it for persistency guarantee. Issue one request for every bytes_per_sync written. 0 turns it off.

Default: 0

You may consider using rate_limiter to regulate write rate to device. When rate limiter is enabled, it automatically enables bytes_per_sync to 1MB.

This option applies to table files

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_bytes_per_sync(1024 * 1024);

pub fn set_wal_bytes_per_sync(&mut self, nbytes: u64)

Same as bytes_per_sync, but applies to WAL files.

Default: 0, turned off

Dynamically changeable through SetDBOptions() API.

pub fn set_writable_file_max_buffer_size(&mut self, nbytes: u64)

Sets the maximum buffer size that is used by WritableFileWriter.

On Windows, we need to maintain an aligned buffer for writes. We allow the buffer to grow until it’s size hits the limit in buffered IO and fix the buffer size when using direct IO to ensure alignment of write requests if the logical sector size is unusual

Default: 1024 * 1024 (1 MB)

Dynamically changeable through SetDBOptions() API.

pub fn set_allow_concurrent_memtable_write(&mut self, allow: bool)

If true, allow multi-writers to update mem tables in parallel. Only some memtable_factory-s support concurrent writes; currently it is implemented only for SkipListFactory. Concurrent memtable writes are not compatible with inplace_update_support or filter_deletes. It is strongly recommended to set enable_write_thread_adaptive_yield if you are going to use this feature.

Default: true

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_allow_concurrent_memtable_write(false);

pub fn set_enable_write_thread_adaptive_yield(&mut self, enabled: bool)

If true, threads synchronizing with the write batch group leader will wait for up to write_thread_max_yield_usec before blocking on a mutex. This can substantially improve throughput for concurrent workloads, regardless of whether allow_concurrent_memtable_write is enabled.

Default: true

pub fn set_max_sequential_skip_in_iterations(&mut self, num: u64)

Specifies whether an iteration->Next() sequentially skips over keys with the same user-key or not.

This number specifies the number of keys (with the same userkey) that will be sequentially skipped before a reseek is issued.

Default: 8

pub fn set_use_direct_reads(&mut self, enabled: bool)

Enable direct I/O mode for reading they may or may not improve performance depending on the use case

Files will be opened in “direct I/O” mode which means that data read from the disk will not be cached or buffered. The hardware buffer of the devices may however still be used. Memory mapped files are not impacted by these parameters.

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_use_direct_reads(true);

pub fn set_use_direct_io_for_flush_and_compaction(&mut self, enabled: bool)

Enable direct I/O mode for flush and compaction

Files will be opened in “direct I/O” mode which means that data written to the disk will not be cached or buffered. The hardware buffer of the devices may however still be used. Memory mapped files are not impacted by these parameters. they may or may not improve performance depending on the use case

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_use_direct_io_for_flush_and_compaction(true);

pub fn set_is_fd_close_on_exec(&mut self, enabled: bool)

Enable/dsiable child process inherit open files.

Default: true

pub fn set_allow_os_buffer(&mut self, is_allow: bool)

👎Deprecated since 0.7.0: replaced with set_use_direct_reads/set_use_direct_io_for_flush_and_compaction methods

Hints to the OS that it should not buffer disk I/O. Enabling this parameter may improve performance but increases pressure on the system cache.

The exact behavior of this parameter is platform dependent.

On POSIX systems, after RocksDB reads data from disk it will mark the pages as “unneeded”. The operating system may - or may not

• evict these pages from memory, reducing pressure on the system cache. If the disk block is requested again this can result in additional disk I/O.

On WINDOWS systems, files will be opened in “unbuffered I/O” mode which means that data read from the disk will not be cached or bufferized. The hardware buffer of the devices may however still be used. Memory mapped files are not impacted by this parameter.

Default: true

Examples

use rocksdb::Options;

let mut opts = Options::default();
#[allow(deprecated)]
opts.set_allow_os_buffer(false);

pub fn set_table_cache_num_shard_bits(&mut self, nbits: c_int)

Sets the number of shards used for table cache.

Default: 6

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_table_cache_num_shard_bits(4);

pub fn set_target_file_size_multiplier(&mut self, multiplier: i32)

By default target_file_size_multiplier is 1, which means by default files in different levels will have similar size.

Dynamically changeable through SetOptions() API

pub fn set_min_write_buffer_number(&mut self, nbuf: c_int)

Sets the minimum number of write buffers that will be merged together before writing to storage. If set to 1, then all write buffers are flushed to L0 as individual files and this increases read amplification because a get request has to check in all of these files. Also, an in-memory merge may result in writing lesser data to storage if there are duplicate records in each of these individual write buffers.

Default: 1

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_min_write_buffer_number(2);

pub fn set_max_write_buffer_number(&mut self, nbuf: c_int)

Sets the maximum number of write buffers that are built up in memory. The default and the minimum number is 2, so that when 1 write buffer is being flushed to storage, new writes can continue to the other write buffer. If max_write_buffer_number > 3, writing will be slowed down to options.delayed_write_rate if we are writing to the last write buffer allowed.

Default: 2

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_max_write_buffer_number(4);

pub fn set_write_buffer_size(&mut self, size: usize)

Sets the 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 max_write_buffer_number 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.

Note that write_buffer_size is enforced per column family. See db_write_buffer_size for sharing memory across column families.

Default: 0x4000000 (64MiB)

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_write_buffer_size(128 * 1024 * 1024);

pub fn set_db_write_buffer_size(&mut self, size: usize)

Amount of data to build up in memtables across all column families before writing to disk.

This is distinct from write_buffer_size, which enforces a limit for a single memtable.

This feature is disabled by default. Specify a non-zero value to enable it.

Default: 0 (disabled)

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_db_write_buffer_size(128 * 1024 * 1024);

pub fn set_max_bytes_for_level_base(&mut self, size: u64)

Control maximum total data size for a level. max_bytes_for_level_base is the max total for level-1. Maximum number of bytes for level L can be calculated as (max_bytes_for_level_base) * (max_bytes_for_level_multiplier ^ (L-1)) For example, if max_bytes_for_level_base is 200MB, and if max_bytes_for_level_multiplier is 10, total data size for level-1 will be 200MB, total file size for level-2 will be 2GB, and total file size for level-3 will be 20GB.

Default: 0x10000000 (256MiB).

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_max_bytes_for_level_base(512 * 1024 * 1024);

pub fn set_max_bytes_for_level_multiplier(&mut self, mul: f64)

Default: 10

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_max_bytes_for_level_multiplier(4.0);

pub fn set_max_manifest_file_size(&mut self, size: usize)

The manifest file is rolled over on reaching this limit. The older manifest file be deleted. The default value is MAX_INT so that roll-over does not take place.

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_max_manifest_file_size(20 * 1024 * 1024);

pub fn set_target_file_size_base(&mut self, size: u64)

Sets the target file size for compaction. target_file_size_base is per-file size for level-1. Target file size for level L can be calculated by target_file_size_base * (target_file_size_multiplier ^ (L-1)) For example, if target_file_size_base is 2MB and target_file_size_multiplier is 10, then each file on level-1 will be 2MB, and each file on level 2 will be 20MB, and each file on level-3 will be 200MB.

Default: 0x4000000 (64MiB)

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_target_file_size_base(128 * 1024 * 1024);

pub fn set_min_write_buffer_number_to_merge(&mut self, to_merge: c_int)

Sets the minimum number of write buffers that will be merged together before writing to storage. If set to 1, then all write buffers are flushed to L0 as individual files and this increases read amplification because a get request has to check in all of these files. Also, an in-memory merge may result in writing lesser data to storage if there are duplicate records in each of these individual write buffers.

Default: 1

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_min_write_buffer_number_to_merge(2);

pub fn set_level_zero_file_num_compaction_trigger(&mut self, n: c_int)

Sets the number of files to trigger level-0 compaction. A value < 0 means that level-0 compaction will not be triggered by number of files at all.

Default: 4

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_level_zero_file_num_compaction_trigger(8);

pub fn set_level_zero_slowdown_writes_trigger(&mut self, n: c_int)

Sets the soft limit on number of level-0 files. We start slowing down writes at this point. A value < 0 means that no writing slow down will be triggered by number of files in level-0.

Default: 20

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_level_zero_slowdown_writes_trigger(10);

pub fn set_level_zero_stop_writes_trigger(&mut self, n: c_int)

Sets the maximum number of level-0 files. We stop writes at this point.

Default: 24

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_level_zero_stop_writes_trigger(48);

pub fn set_compaction_style(&mut self, style: DBCompactionStyle)

Sets the compaction style.

Default: DBCompactionStyle::Level

Examples

use rocksdb::{Options, DBCompactionStyle};

let mut opts = Options::default();
opts.set_compaction_style(DBCompactionStyle::Universal);

pub fn set_universal_compaction_options( &mut self, uco: &UniversalCompactOptions, )

Sets the options needed to support Universal Style compactions.

pub fn set_fifo_compaction_options(&mut self, fco: &FifoCompactOptions)

Sets the options for FIFO compaction style.

pub fn set_unordered_write(&mut self, unordered: bool)

Sets unordered_write to true trades higher write throughput with relaxing the immutability guarantee of snapshots. This violates the repeatability one expects from ::Get from a snapshot, as well as ::MultiGet and Iterator’s consistent-point-in-time view property. If the application cannot tolerate the relaxed guarantees, it can implement its own mechanisms to work around that and yet benefit from the higher throughput. Using TransactionDB with WRITE_PREPARED write policy and two_write_queues=true is one way to achieve immutable snapshots despite unordered_write.

By default, i.e., when it is false, rocksdb does not advance the sequence number for new snapshots unless all the writes with lower sequence numbers are already finished. This provides the immutability that we except from snapshots. Moreover, since Iterator and MultiGet internally depend on snapshots, the snapshot immutability results into Iterator and MultiGet offering consistent-point-in-time view. If set to true, although Read-Your-Own-Write property is still provided, the snapshot immutability property is relaxed: the writes issued after the snapshot is obtained (with larger sequence numbers) will be still not visible to the reads from that snapshot, however, there still might be pending writes (with lower sequence number) that will change the state visible to the snapshot after they are landed to the memtable.

Default: false

pub fn set_max_subcompactions(&mut self, num: u32)

Sets maximum number of threads that will concurrently perform a compaction job by breaking it into multiple, smaller ones that are run simultaneously.

Default: 1 (i.e. no subcompactions)

pub fn set_max_background_jobs(&mut self, jobs: c_int)

Sets maximum number of concurrent background jobs (compactions and flushes).

Default: 2

Dynamically changeable through SetDBOptions() API.

pub fn set_max_background_compactions(&mut self, n: c_int)

👎Deprecated since 0.15.0: RocksDB automatically decides this based on the value of max_background_jobs

Sets the maximum number of concurrent background compaction jobs, submitted to the default LOW priority thread pool. We first try to schedule compactions based on base_background_compactions. If the compaction cannot catch up , we will increase number of compaction threads up to max_background_compactions.

If you’re increasing this, also consider increasing number of threads in LOW priority thread pool. For more information, see Env::SetBackgroundThreads

Default: 1

Examples

use rocksdb::Options;

let mut opts = Options::default();
#[allow(deprecated)]
opts.set_max_background_compactions(2);

pub fn set_max_background_flushes(&mut self, n: c_int)

👎Deprecated since 0.15.0: RocksDB automatically decides this based on the value of max_background_jobs

Sets the maximum number of concurrent background memtable flush jobs, submitted to the HIGH priority thread pool.

By default, all background jobs (major compaction and memtable flush) go to the LOW priority pool. If this option is set to a positive number, memtable flush jobs will be submitted to the HIGH priority pool. It is important when the same Env is shared by multiple db instances. Without a separate pool, long running major compaction jobs could potentially block memtable flush jobs of other db instances, leading to unnecessary Put stalls.

If you’re increasing this, also consider increasing number of threads in HIGH priority thread pool. For more information, see Env::SetBackgroundThreads

Default: 1

Examples

use rocksdb::Options;

let mut opts = Options::default();
#[allow(deprecated)]
opts.set_max_background_flushes(2);

pub fn set_disable_auto_compactions(&mut self, disable: bool)

Disables automatic compactions. Manual compactions can still be issued on this column family

Default: false

Dynamically changeable through SetOptions() API

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_disable_auto_compactions(true);

pub fn set_memtable_huge_page_size(&mut self, size: size_t)

SetMemtableHugePageSize sets the page size for huge page for arena used by the memtable. If <=0, it won’t allocate from huge page but from malloc. Users are responsible to reserve huge pages for it to be allocated. For example: sysctl -w vm.nr_hugepages=20 See linux doc Documentation/vm/hugetlbpage.txt If there isn’t enough free huge page available, it will fall back to malloc.

Dynamically changeable through SetOptions() API

pub fn set_max_successive_merges(&mut self, num: usize)

Sets the maximum number of successive merge operations on a key in the memtable.

When a merge operation is added to the memtable and the maximum number of successive merges is reached, the value of the key will be calculated and inserted into the memtable instead of the merge operation. This will ensure that there are never more than max_successive_merges merge operations in the memtable.

Default: 0 (disabled)

pub fn set_bloom_locality(&mut self, v: u32)

Control locality of bloom filter probes to improve cache miss rate. This option only applies to memtable prefix bloom and plaintable prefix bloom. It essentially limits the max number of cache lines each bloom filter check can touch.

This optimization is turned off when set to 0. The number should never be greater than number of probes. This option can boost performance for in-memory workload but should use with care since it can cause higher false positive rate.

Default: 0

pub fn set_inplace_update_support(&mut self, enabled: bool)

Enable/disable thread-safe inplace updates.

Requires updates if

• key exists in current memtable
• new sizeof(new_value) <= sizeof(old_value)
• old_value for that key is a put i.e. kTypeValue

Default: false.

pub fn set_inplace_update_locks(&mut self, num: usize)

Sets the number of locks used for inplace update.

Default: 10000 when inplace_update_support = true, otherwise 0.

pub fn set_max_bytes_for_level_multiplier_additional( &mut self, level_values: &[i32], )

Different max-size multipliers for different levels. These are multiplied by max_bytes_for_level_multiplier to arrive at the max-size of each level.

Default: 1

Dynamically changeable through SetOptions() API

pub fn set_skip_checking_sst_file_sizes_on_db_open(&mut self, value: bool)

If true, then DB::Open() will not fetch and check sizes of all sst files. This may significantly speed up startup if there are many sst files, especially when using non-default Env with expensive GetFileSize(). We’ll still check that all required sst files exist. If paranoid_checks is false, this option is ignored, and sst files are not checked at all.

Default: false

pub fn set_max_write_buffer_size_to_maintain(&mut self, size: i64)

The total maximum size(bytes) of write buffers to maintain in memory including copies of buffers that have already been flushed. This parameter only affects trimming of flushed buffers and does not affect flushing. This controls the maximum amount of write history that will be available in memory for conflict checking when Transactions are used. The actual size of write history (flushed Memtables) might be higher than this limit if further trimming will reduce write history total size below this limit. For example, if max_write_buffer_size_to_maintain is set to 64MB, and there are three flushed Memtables, with sizes of 32MB, 20MB, 20MB. Because trimming the next Memtable of size 20MB will reduce total memory usage to 52MB which is below the limit, RocksDB will stop trimming.

When using an OptimisticTransactionDB: If this value is too low, some transactions may fail at commit time due to not being able to determine whether there were any write conflicts.

When using a TransactionDB: If Transaction::SetSnapshot is used, TransactionDB will read either in-memory write buffers or SST files to do write-conflict checking. Increasing this value can reduce the number of reads to SST files done for conflict detection.

Setting this value to 0 will cause write buffers to be freed immediately after they are flushed. If this value is set to -1, ‘max_write_buffer_number * write_buffer_size’ will be used.

Default: If using a TransactionDB/OptimisticTransactionDB, the default value will be set to the value of ‘max_write_buffer_number * write_buffer_size’ if it is not explicitly set by the user. Otherwise, the default is 0.

pub fn set_enable_pipelined_write(&mut self, value: bool)

By default, a single write thread queue is maintained. The thread gets to the head of the queue becomes write batch group leader and responsible for writing to WAL and memtable for the batch group.

If enable_pipelined_write is true, separate write thread queue is maintained for WAL write and memtable write. A write thread first enter WAL writer queue and then memtable writer queue. Pending thread on the WAL writer queue thus only have to wait for previous writers to finish their WAL writing but not the memtable writing. Enabling the feature may improve write throughput and reduce latency of the prepare phase of two-phase commit.

Default: false

pub fn set_memtable_factory(&mut self, factory: MemtableFactory)

Defines the underlying memtable implementation. See official wiki for more information. Defaults to using a skiplist.

Examples

use rocksdb::{Options, MemtableFactory};
let mut opts = Options::default();
let factory = MemtableFactory::HashSkipList {
    bucket_count: 1_000_000,
    height: 4,
    branching_factor: 4,
};

opts.set_allow_concurrent_memtable_write(false);
opts.set_memtable_factory(factory);

pub fn set_block_based_table_factory(&mut self, factory: &BlockBasedOptions)

pub fn set_cuckoo_table_factory(&mut self, factory: &CuckooTableOptions)

Sets the table factory to a CuckooTableFactory (the default table factory is a block-based table factory that provides a default implementation of TableBuilder and TableReader with default BlockBasedTableOptions). See official wiki for more information on this table format.

Examples

use rocksdb::{Options, CuckooTableOptions};

let mut opts = Options::default();
let mut factory_opts = CuckooTableOptions::default();
factory_opts.set_hash_ratio(0.8);
factory_opts.set_max_search_depth(20);
factory_opts.set_cuckoo_block_size(10);
factory_opts.set_identity_as_first_hash(true);
factory_opts.set_use_module_hash(false);

opts.set_cuckoo_table_factory(&factory_opts);

pub fn set_plain_table_factory(&mut self, options: &PlainTableFactoryOptions)

Sets the factory as plain table. See official wiki for more information.

Examples

use rocksdb::{Options, PlainTableFactoryOptions};

let mut opts = Options::default();
let factory_opts = PlainTableFactoryOptions {
  user_key_length: 0,
  bloom_bits_per_key: 20,
  hash_table_ratio: 0.75,
  index_sparseness: 16,
};

opts.set_plain_table_factory(&factory_opts);

pub fn set_min_level_to_compress(&mut self, lvl: c_int)

Sets the start level to use compression.

pub fn set_report_bg_io_stats(&mut self, enable: bool)

Measure IO stats in compactions and flushes, if true.

Default: false

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_report_bg_io_stats(true);

pub fn set_max_total_wal_size(&mut self, size: u64)

Once write-ahead logs exceed this size, we will start forcing the flush of column families whose memtables are backed by the oldest live WAL file (i.e. the ones that are causing all the space amplification).

Default: 0

Examples

use rocksdb::Options;

let mut opts = Options::default();
// Set max total wal size to 1G.
opts.set_max_total_wal_size(1 << 30);

pub fn set_wal_recovery_mode(&mut self, mode: DBRecoveryMode)

Recovery mode to control the consistency while replaying WAL.

Default: DBRecoveryMode::PointInTime

Examples

use rocksdb::{Options, DBRecoveryMode};

let mut opts = Options::default();
opts.set_wal_recovery_mode(DBRecoveryMode::AbsoluteConsistency);

pub fn enable_statistics(&mut self)

pub fn get_statistics(&self) -> Option<String>

pub fn set_stats_dump_period_sec(&mut self, period: c_uint)

If not zero, dump rocksdb.stats to LOG every stats_dump_period_sec.

Default: 600 (10 mins)

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_stats_dump_period_sec(300);

pub fn set_stats_persist_period_sec(&mut self, period: c_uint)

If not zero, dump rocksdb.stats to RocksDB to LOG every stats_persist_period_sec.

Default: 600 (10 mins)

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_stats_persist_period_sec(5);

pub fn set_advise_random_on_open(&mut self, advise: bool)

When set to true, reading SST files will opt out of the filesystem’s readahead. Setting this to false may improve sequential iteration performance.

Default: true

pub fn set_access_hint_on_compaction_start(&mut self, pattern: AccessHint)

Specifies the file access pattern once a compaction is started.

It will be applied to all input files of a compaction.

Default: Normal

pub fn set_use_adaptive_mutex(&mut self, enabled: bool)

Enable/disable adaptive mutex, which spins in the user space before resorting to kernel.

This could reduce context switch when the mutex is not heavily contended. However, if the mutex is hot, we could end up wasting spin time.

Default: false

pub fn set_num_levels(&mut self, n: c_int)

Sets the number of levels for this database.

pub fn set_memtable_prefix_bloom_ratio(&mut self, ratio: f64)

When a prefix_extractor is defined through opts.set_prefix_extractor this creates a prefix bloom filter for each memtable with the size of write_buffer_size * memtable_prefix_bloom_ratio (capped at 0.25).

Default: 0

Examples

use rocksdb::{Options, SliceTransform};

let mut opts = Options::default();
let transform = SliceTransform::create_fixed_prefix(10);
opts.set_prefix_extractor(transform);
opts.set_memtable_prefix_bloom_ratio(0.2);

pub fn set_max_compaction_bytes(&mut self, nbytes: u64)

Sets the maximum number of bytes in all compacted files. We try to limit number of bytes in one compaction to be lower than this threshold. But it’s not guaranteed.

Value 0 will be sanitized.

Default: target_file_size_base * 25

pub fn set_wal_dir<P: AsRef<Path>>(&mut self, path: P)

Specifies the absolute path of the directory the write-ahead log (WAL) should be written to.

Default: same directory as the database

Examples

use rocksdb::Options;

let mut opts = Options::default();
opts.set_wal_dir("/path/to/dir");

pub fn set_wal_ttl_seconds(&mut self, secs: u64)

Sets the WAL ttl in seconds.

The following two options affect how archived logs will be deleted.

1. If both set to 0, logs will be deleted asap and will not get into the archive.
2. If wal_ttl_seconds is 0 and wal_size_limit_mb is not 0, WAL files will be checked every 10 min and if total size is greater then wal_size_limit_mb, they will be deleted starting with the earliest until size_limit is met. All empty files will be deleted.
3. If wal_ttl_seconds is not 0 and wall_size_limit_mb is 0, then WAL files will be checked every wal_ttl_seconds / 2 and those that are older than wal_ttl_seconds will be deleted.
4. If both are not 0, WAL files will be checked every 10 min and both checks will be performed with ttl being first.

Default: 0

pub fn set_wal_size_limit_mb(&mut self, size: u64)

Sets the WAL size limit in MB.

If total size of WAL files is greater then wal_size_limit_mb, they will be deleted starting with the earliest until size_limit is met.

Default: 0

pub fn set_manifest_preallocation_size(&mut self, size: usize)

Sets the number of bytes to preallocate (via fallocate) the manifest files.

Default is 4MB, which is reasonable to reduce random IO as well as prevent overallocation for mounts that preallocate large amounts of data (such as xfs’s allocsize option).

pub fn set_skip_stats_update_on_db_open(&mut self, skip: bool)

If true, then DB::Open() will not update the statistics used to optimize compaction decision by loading table properties from many files. Turning off this feature will improve DBOpen time especially in disk environment.

Default: false

pub fn set_keep_log_file_num(&mut self, nfiles: usize)

Specify the maximal number of info log files to be kept.

Default: 1000

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_keep_log_file_num(100);

pub fn set_allow_mmap_writes(&mut self, is_enabled: bool)

Allow the OS to mmap file for writing.

Default: false

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_allow_mmap_writes(true);

pub fn set_allow_mmap_reads(&mut self, is_enabled: bool)

Allow the OS to mmap file for reading sst tables.

Default: false

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_allow_mmap_reads(true);

pub fn set_manual_wal_flush(&mut self, is_enabled: bool)

If enabled, WAL is not flushed automatically after each write. Instead it relies on manual invocation of DB::flush_wal() to write the WAL buffer to its file.

Default: false

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_manual_wal_flush(true);

pub fn set_atomic_flush(&mut self, atomic_flush: bool)

Guarantee that all column families are flushed together atomically. This option applies to both manual flushes (db.flush()) and automatic background flushes caused when memtables are filled.

Note that this is only useful when the WAL is disabled. When using the WAL, writes are always consistent across column families.

Default: false

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_atomic_flush(true);

pub fn set_row_cache(&mut self, cache: &Cache)

Sets global cache for table-level rows. Cache must outlive DB instance which uses it.

Default: null (disabled) Not supported in ROCKSDB_LITE mode!

pub fn set_ratelimiter( &mut self, rate_bytes_per_sec: i64, refill_period_us: i64, fairness: i32, )

Use to control write rate of flush and compaction. Flush has higher priority than compaction. If rate limiter is enabled, bytes_per_sync is set to 1MB by default.

Default: disable

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_ratelimiter(1024 * 1024, 100 * 1000, 10);

pub fn set_max_log_file_size(&mut self, size: usize)

Sets the maximal size of the info log file.

If the log file is larger than max_log_file_size, a new info log file will be created. If max_log_file_size is equal to zero, all logs will be written to one log file.

Default: 0

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_max_log_file_size(0);

pub fn set_log_file_time_to_roll(&mut self, secs: usize)

Sets the time for the info log file to roll (in seconds).

If specified with non-zero value, log file will be rolled if it has been active longer than log_file_time_to_roll. Default: 0 (disabled)

pub fn set_recycle_log_file_num(&mut self, num: usize)

Controls the recycling of log files.

If non-zero, previously written log files will be reused for new logs, overwriting the old data. The value indicates how many such files we will keep around at any point in time for later use. This is more efficient because the blocks are already allocated and fdatasync does not need to update the inode after each write.

Default: 0

Examples

use rocksdb::Options;

let mut options = Options::default();
options.set_recycle_log_file_num(5);

pub fn set_soft_pending_compaction_bytes_limit(&mut self, limit: usize)

Sets the threshold at which all writes will be slowed down to at least delayed_write_rate if estimated bytes needed to be compaction exceed this threshold.

Default: 64GB

pub fn set_hard_pending_compaction_bytes_limit(&mut self, limit: usize)

Sets the bytes threshold at which all writes are stopped if estimated bytes needed to be compaction exceed this threshold.

Default: 256GB

pub fn set_arena_block_size(&mut self, size: usize)

Sets the size of one block in arena memory allocation.

If <= 0, a proper value is automatically calculated (usually 1/10 of writer_buffer_size).

Default: 0

pub fn set_dump_malloc_stats(&mut self, enabled: bool)

If true, then print malloc stats together with rocksdb.stats when printing to LOG.

Default: false

pub fn set_memtable_whole_key_filtering(&mut self, whole_key_filter: bool)

Enable whole key bloom filter in memtable. Note this will only take effect if memtable_prefix_bloom_size_ratio is not 0. Enabling whole key filtering can potentially reduce CPU usage for point-look-ups.

Default: false (disable)

Dynamically changeable through SetOptions() API

pub fn set_enable_blob_files(&mut self, val: bool)

Enable the use of key-value separation.

More details can be found here: Integrated BlobDB.

Default: false (disable)

Dynamically changeable through SetOptions() API

pub fn set_min_blob_size(&mut self, val: u64)

Sets the minimum threshold value at or above which will be written to blob files during flush or compaction.

Dynamically changeable through SetOptions() API

pub fn set_blob_file_size(&mut self, val: u64)

Sets the size limit for blob files.

Dynamically changeable through SetOptions() API

pub fn set_blob_compression_type(&mut self, val: DBCompressionType)

Sets the blob compression type. All blob files use the same compression type.

Dynamically changeable through SetOptions() API

pub fn set_enable_blob_gc(&mut self, val: bool)

If this is set to true RocksDB will actively relocate valid blobs from the oldest blob files as they are encountered during compaction.

Dynamically changeable through SetOptions() API

pub fn set_blob_gc_age_cutoff(&mut self, val: c_double)

Sets the threshold that the GC logic uses to determine which blob files should be considered “old.”

For example, the default value of 0.25 signals to RocksDB that blobs residing in the oldest 25% of blob files should be relocated by GC. This parameter can be tuned to adjust the trade-off between write amplification and space amplification.

Dynamically changeable through SetOptions() API

pub fn set_blob_gc_force_threshold(&mut self, val: c_double)

Sets the blob GC force threshold.

Dynamically changeable through SetOptions() API

pub fn set_blob_compaction_readahead_size(&mut self, val: u64)

Sets the blob compaction read ahead size.

Dynamically changeable through SetOptions() API

Trait Implementations

impl Clone for Options

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Default for Options

fn default() -> Self

Returns the “default value” for a type.

impl Drop for Options

fn drop(&mut self)

Executes the destructor for this type.

impl Send for Options

impl Sync for Options