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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.
#include <stddef.h>
#include <stdint.h>
#include <string>
#include <memory>
#include <vector>
#include <limits>
#include <unordered_map>
#include "rocksdb/advanced_options.h"
#include "rocksdb/comparator.h"
#include "rocksdb/env.h"
#include "rocksdb/listener.h"
#include "rocksdb/universal_compaction.h"
#include "rocksdb/version.h"
#include "rocksdb/write_buffer_manager.h"
#ifdef max
#undef max
namespace rocksdb {
class Cache;
class CompactionFilter;
class CompactionFilterFactory;
class Comparator;
class Env;
enum InfoLogLevel : unsigned char;
class SstFileManager;
class FilterPolicy;
class Logger;
class MergeOperator;
class Snapshot;
class MemTableRepFactory;
class RateLimiter;
class Slice;
class Statistics;
class InternalKeyComparator;
class WalFilter;
// DB contents are stored in a set of blocks, each of which holds a
// sequence of key,value pairs. Each block may be compressed before
// being stored in a file. The following enum describes which
// compression method (if any) is used to compress a block.
enum CompressionType : unsigned char {
// NOTE: do not change the values of existing entries, as these are
// part of the persistent format on disk.
kNoCompression = 0x0,
kSnappyCompression = 0x1,
kZlibCompression = 0x2,
kBZip2Compression = 0x3,
kLZ4Compression = 0x4,
kLZ4HCCompression = 0x5,
kXpressCompression = 0x6,
kZSTD = 0x7,
// Only use kZSTDNotFinalCompression if you have to use ZSTD lib older than
// 0.8.0 or consider a possibility of downgrading the service or copying
// the database files to another service running with an older version of
// RocksDB that doesn't have kZSTD. Otherwise, you should use kZSTD. We will
// eventually remove the option from the public API.
kZSTDNotFinalCompression = 0x40,
// kDisableCompressionOption is used to disable some compression options.
kDisableCompressionOption = 0xff,
struct Options;
struct DbPath;
struct ColumnFamilyOptions : public AdvancedColumnFamilyOptions {
// The function recovers options to a previous version. Only 4.6 or later
// versions are supported.
ColumnFamilyOptions* OldDefaults(int rocksdb_major_version = 4,
int rocksdb_minor_version = 6);
// Some functions that make it easier to optimize RocksDB
// Use this if your DB is very small (like under 1GB) and you don't want to
// spend lots of memory for memtables.
ColumnFamilyOptions* OptimizeForSmallDb();
// Use this if you don't need to keep the data sorted, i.e. you'll never use
// an iterator, only Put() and Get() API calls
// Not supported in ROCKSDB_LITE
ColumnFamilyOptions* OptimizeForPointLookup(
uint64_t block_cache_size_mb);
// Default values for some parameters in ColumnFamilyOptions are not
// optimized for heavy workloads and big datasets, which means you might
// observe write stalls under some conditions. As a starting point for tuning
// RocksDB options, use the following two functions:
// * OptimizeLevelStyleCompaction -- optimizes level style compaction
// * OptimizeUniversalStyleCompaction -- optimizes universal style compaction
// Universal style compaction is focused on reducing Write Amplification
// Factor for big data sets, but increases Space Amplification. You can learn
// more about the different styles here:
// Make sure to also call IncreaseParallelism(), which will provide the
// biggest performance gains.
// Note: we might use more memory than memtable_memory_budget during high
// write rate period
// OptimizeUniversalStyleCompaction is not supported in ROCKSDB_LITE
ColumnFamilyOptions* OptimizeLevelStyleCompaction(
uint64_t memtable_memory_budget = 512 * 1024 * 1024);
ColumnFamilyOptions* OptimizeUniversalStyleCompaction(
uint64_t memtable_memory_budget = 512 * 1024 * 1024);
// -------------------
// 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 = BytewiseComparator();
// REQUIRES: The client must provide a merge operator if Merge operation
// needs to be accessed. Calling Merge on a DB without a merge operator
// would result in Status::NotSupported. The client must ensure that the
// merge operator supplied here has the same name and *exactly* the same
// semantics as the merge operator provided to previous open calls on
// the same DB. The only exception is reserved for upgrade, where a DB
// previously without a merge operator is introduced to Merge operation
// for the first time. It's necessary to specify a merge operator when
// opening the DB in this case.
// Default: nullptr
std::shared_ptr<MergeOperator> merge_operator = nullptr;
// A single CompactionFilter instance to call into during compaction.
// Allows an application to modify/delete a key-value during background
// compaction.
// If the client requires a new compaction filter to be used for different
// compaction runs, it can specify compaction_filter_factory instead of this
// option. The client should specify only one of the two.
// compaction_filter takes precedence over compaction_filter_factory if
// client specifies both.
// If multithreaded compaction is being used, the supplied CompactionFilter
// instance may be used from different threads concurrently and so should be
// thread-safe.
// Default: nullptr
const CompactionFilter* compaction_filter = nullptr;
// 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
std::shared_ptr<CompactionFilterFactory> compaction_filter_factory = nullptr;
// -------------------
// 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 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: 64MB
// Dynamically changeable through SetOptions() API
size_t write_buffer_size = 64 << 20;
// Compress blocks using the specified compression algorithm. This
// parameter can be changed dynamically.
// Default: kSnappyCompression, if it's supported. If snappy is not linked
// with the library, the default is kNoCompression.
// 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.
// If you do not set `compression_opts.level`, or set it to
// `CompressionOptions::kDefaultCompressionLevel`, we will attempt to pick the
// default corresponding to `compression` as follows:
// - kZSTD: 3
// - kZlibCompression: Z_DEFAULT_COMPRESSION (currently -1)
// - kLZ4HCCompression: 0
// - For all others, we do not specify a compression level
CompressionType compression;
// Compression algorithm that will be used for the bottommost level that
// contain files.
// Default: kDisableCompressionOption (Disabled)
CompressionType bottommost_compression = kDisableCompressionOption;
// different options for compression algorithms used by bottommost_compression
// if it is enabled. To enable it, please see the definition of
// CompressionOptions.
CompressionOptions bottommost_compression_opts;
// different options for compression algorithms
CompressionOptions compression_opts;
// 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
int level0_file_num_compaction_trigger = 4;
// If non-nullptr, use the specified function to determine the
// prefixes for keys. These prefixes will be placed in the filter.
// Depending on the workload, this can reduce the number of read-IOP
// cost for scans when a prefix is passed via ReadOptions to
// db.NewIterator(). For prefix filtering to work properly,
// "prefix_extractor" and "comparator" must be such that the following
// properties hold:
// 1) key.starts_with(prefix(key))
// 2) Compare(prefix(key), key) <= 0.
// 3) If Compare(k1, k2) <= 0, then Compare(prefix(k1), prefix(k2)) <= 0
// 4) prefix(prefix(key)) == prefix(key)
// Default: nullptr
std::shared_ptr<const SliceTransform> prefix_extractor = nullptr;
// 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: 256MB.
// Dynamically changeable through SetOptions() API
uint64_t max_bytes_for_level_base = 256 * 1048576;
// Disable automatic compactions. Manual compactions can still
// be issued on this column family
// Dynamically changeable through SetOptions() API
bool disable_auto_compactions = false;
// This is a factory that provides TableFactory objects.
// Default: a block-based table factory that provides a default
// implementation of TableBuilder and TableReader with default
// BlockBasedTableOptions.
std::shared_ptr<TableFactory> table_factory;
// A list of paths where SST files for this column family
// can be put into, with its target size. Similar to db_paths,
// newer data is placed into paths specified earlier in the
// vector while older data gradually moves to paths specified
// later in the vector.
// Note that, if a path is supplied to multiple column
// families, it would have files and total size from all
// the column families combined. User should provision for the
// total size(from all the column families) in such cases.
// If left empty, db_paths will be used.
// Default: empty
std::vector<DbPath> cf_paths;
// Create ColumnFamilyOptions with default values for all fields
// Create ColumnFamilyOptions from Options
explicit ColumnFamilyOptions(const Options& options);
void Dump(Logger* log) const;
enum class WALRecoveryMode : char {
// Original levelDB recovery
// We tolerate incomplete record in trailing data on all logs
// Use case : This is legacy behavior
kTolerateCorruptedTailRecords = 0x00,
// Recover from clean shutdown
// We don't expect to find any corruption in the WAL
// Use case : This is ideal for unit tests and rare applications that
// can require high consistency guarantee
kAbsoluteConsistency = 0x01,
// Recover to point-in-time consistency (default)
// We stop the WAL playback on discovering WAL inconsistency
// Use case : Ideal for systems that have disk controller cache like
// hard disk, SSD without super capacitor that store related data
kPointInTimeRecovery = 0x02,
// Recovery after a disaster
// We ignore any corruption in the WAL and try to salvage as much data as
// possible
// Use case : Ideal for last ditch effort to recover data or systems that
// operate with low grade unrelated data
kSkipAnyCorruptedRecords = 0x03,
struct DbPath {
std::string path;
uint64_t target_size; // Target size of total files under the path, in byte.
DbPath() : target_size(0) {}
DbPath(const std::string& p, uint64_t t) : path(p), target_size(t) {}
struct DBOptions {
// The function recovers options to the option as in version 4.6.
DBOptions* OldDefaults(int rocksdb_major_version = 4,
int rocksdb_minor_version = 6);
// Some functions that make it easier to optimize RocksDB
// Use this if your DB is very small (like under 1GB) and you don't want to
// spend lots of memory for memtables.
DBOptions* OptimizeForSmallDb();
// 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.
DBOptions* IncreaseParallelism(int total_threads = 16);
#endif // ROCKSDB_LITE
// If true, the database will be created if it is missing.
// Default: false
bool create_if_missing = false;
// If true, missing column families will be automatically created.
// Default: false
bool create_missing_column_families = false;
// If true, an error is raised if the database already exists.
// Default: false
bool error_if_exists = false;
// If true, RocksDB will aggressively check consistency of the data.
// Also, 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.
// In most cases you want this to be set to true.
// Default: true
bool paranoid_checks = true;
// Use the specified object to interact with the environment,
// e.g. to read/write files, schedule background work, etc.
// Default: Env::Default()
Env* env = Env::Default();
// Use to control write rate of flush and compaction. Flush has higher
// priority than compaction. Rate limiting is disabled if nullptr.
// If rate limiter is enabled, bytes_per_sync is set to 1MB by default.
// Default: nullptr
std::shared_ptr<RateLimiter> rate_limiter = nullptr;
// Use to track SST files and control their file deletion rate.
// Features:
// - Throttle the deletion rate of the SST files.
// - Keep track the total size of all SST files.
// - Set a maximum allowed space limit for SST files that when reached
// the DB wont do any further flushes or compactions and will set the
// background error.
// - Can be shared between multiple dbs.
// Limitations:
// - Only track and throttle deletes of SST files in
// first db_path (db_name if db_paths is empty).
// Default: nullptr
std::shared_ptr<SstFileManager> sst_file_manager = nullptr;
// Any internal progress/error information generated by the db will
// be written to info_log if it is non-nullptr, or to a file stored
// in the same directory as the DB contents if info_log is nullptr.
// Default: nullptr
std::shared_ptr<Logger> info_log = nullptr;
#ifdef NDEBUG
InfoLogLevel info_log_level = INFO_LEVEL;
InfoLogLevel info_log_level = DEBUG_LEVEL;
#endif // NDEBUG
// 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
int max_open_files = -1;
// 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
int max_file_opening_threads = 16;
// 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). If set to 0
// (default), we will dynamically choose the WAL size limit to be
// [sum of all write_buffer_size * max_write_buffer_number] * 4
// Default: 0
uint64_t max_total_wal_size = 0;
// If non-null, then we should collect metrics about database operations
std::shared_ptr<Statistics> statistics = nullptr;
// 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.
bool use_fsync = false;
// 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 db_name passed when
// opening the DB.
// Default: empty
std::vector<DbPath> db_paths;
// This specifies the 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.
std::string db_log_dir = "";
// This specifies the absolute dir path for write-ahead logs (WAL).
// If it is empty, the log files will be in the same dir as data,
// dbname is used as the data dir by default
// If it is non empty, the log files will be in kept the specified dir.
// When destroying the db,
// all log files in wal_dir and the dir itself is deleted
std::string wal_dir = "";
// The periodicity when obsolete files get deleted. The default
// value is 6 hours. The files that get out of scope by compaction
// process will still get automatically delete on every compaction,
// regardless of this setting
uint64_t delete_obsolete_files_period_micros = 6ULL * 60 * 60 * 1000000;
// Maximum number of concurrent background jobs (compactions and flushes).
int max_background_jobs = 2;
// NOT SUPPORTED ANYMORE: RocksDB automatically decides this based on the
// value of max_background_jobs. This option is ignored.
int base_background_compactions = -1;
// NOT SUPPORTED ANYMORE: RocksDB automatically decides this based on the
// value of max_background_jobs. For backwards compatibility we will set
// `max_background_jobs = max_background_compactions + max_background_flushes`
// in the case where user sets at least one of `max_background_compactions` or
// `max_background_flushes` (we replace -1 by 1 in case one option is unset).
// Maximum number of concurrent background compaction jobs, submitted to
// the default LOW priority thread pool.
// If you're increasing this, also consider increasing number of threads in
// LOW priority thread pool. For more information, see
// Env::SetBackgroundThreads
// Default: -1
int max_background_compactions = -1;
// This value represents the 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)
uint32_t max_subcompactions = 1;
// NOT SUPPORTED ANYMORE: RocksDB automatically decides this based on the
// value of max_background_jobs. For backwards compatibility we will set
// `max_background_jobs = max_background_compactions + max_background_flushes`
// in the case where user sets at least one of `max_background_compactions` or
// `max_background_flushes`.
// Maximum number of concurrent background memtable flush jobs, submitted by
// default to the HIGH priority thread pool. If the HIGH priority thread pool
// is configured to have zero threads, flush jobs will share the LOW priority
// thread pool with compaction jobs.
// It is important to use both thread pools when the same Env is shared by
// multiple db instances. Without a separate pool, long running 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
int max_background_flushes = -1;
// Specify 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 == 0, all logs will be written to one
// log file.
size_t max_log_file_size = 0;
// 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)
// Not supported in ROCKSDB_LITE mode!
size_t log_file_time_to_roll = 0;
// Maximal info log files to be kept.
// Default: 1000
size_t keep_log_file_num = 1000;
// Recycle log files.
// If non-zero, we will reuse previously written log files 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
size_t recycle_log_file_num = 0;
// manifest file is rolled over on reaching this limit.
// The older manifest file be deleted.
// The default value is 1GB so that the manifest file can grow, but not
// reach the limit of storage capacity.
uint64_t max_manifest_file_size = 1024 * 1024 * 1024;
// Number of shards used for table cache.
int table_cache_numshardbits = 6;
// int table_cache_remove_scan_count_limit;
// The following two fields 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 WAL_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.
uint64_t WAL_ttl_seconds = 0;
uint64_t WAL_size_limit_MB = 0;
// 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).
size_t manifest_preallocation_size = 4 * 1024 * 1024;
// Allow the OS to mmap file for reading sst tables. Default: false
bool allow_mmap_reads = false;
// Allow the OS to mmap file for writing.
// DB::SyncWAL() only works if this is set to false.
// Default: false
bool allow_mmap_writes = false;
// Enable direct I/O mode for read/write
// 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 r/w 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.
// Use O_DIRECT for user and compaction reads.
// When true, we also force new_table_reader_for_compaction_inputs to true.
// Default: false
// Not supported in ROCKSDB_LITE mode!
bool use_direct_reads = false;
// Use O_DIRECT for writes in background flush and compactions.
// Default: false
// Not supported in ROCKSDB_LITE mode!
bool use_direct_io_for_flush_and_compaction = false;
// If false, fallocate() calls are bypassed
bool allow_fallocate = true;
// Disable child process inherit open files. Default: true
bool is_fd_close_on_exec = true;
// NOT SUPPORTED ANYMORE -- this options is no longer used
bool skip_log_error_on_recovery = false;
// if not zero, dump rocksdb.stats to LOG every stats_dump_period_sec
// Default: 600 (10 min)
unsigned int stats_dump_period_sec = 600;
// If set true, will hint the underlying file system that the file
// access pattern is random, when a sst file is opened.
// Default: true
bool advise_random_on_open = true;
// 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)
size_t db_write_buffer_size = 0;
// The memory usage of memtable will report to this object. The same object
// can be passed into multiple DBs and it will track the sum of size of all
// the DBs. If the total size of all live memtables of all the DBs exceeds
// a limit, a flush will be triggered in the next DB to which the next write
// is issued.
// If the object is only passed to on DB, the behavior is the same as
// db_write_buffer_size. When write_buffer_manager is set, the value set will
// override db_write_buffer_size.
// This feature is disabled by default. Specify a non-zero value
// to enable it.
// Default: null
std::shared_ptr<WriteBufferManager> write_buffer_manager = nullptr;
// Specify the file access pattern once a compaction is started.
// It will be applied to all input files of a compaction.
// Default: NORMAL
enum AccessHint {
AccessHint access_hint_on_compaction_start = NORMAL;
// If true, always create a new file descriptor and new table reader
// for compaction inputs. Turn this parameter on may introduce extra
// memory usage in the table reader, if it allocates extra memory
// for indexes. This will allow file descriptor prefetch options
// to be set for compaction input files and not to impact file
// descriptors for the same file used by user queries.
// Suggest to enable BlockBasedTableOptions.cache_index_and_filter_blocks
// for this mode if using block-based table.
// Default: false
bool new_table_reader_for_compaction_inputs = false;
// 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
size_t compaction_readahead_size = 0;
// This is a maximum buffer size that is used by WinMmapReadableFile in
// unbuffered disk I/O mode. We need to maintain an aligned buffer for
// reads. We allow the buffer to grow until the specified value and then
// for bigger requests allocate one shot buffers. In unbuffered mode we
// always bypass read-ahead buffer at ReadaheadRandomAccessFile
// When read-ahead is required we then make use of compaction_readahead_size
// value and always try to read ahead. With read-ahead we always
// pre-allocate buffer to the size instead of growing it up to a limit.
// This option is currently honored only on Windows
// Default: 1 Mb
// Special value: 0 - means do not maintain per instance buffer. Allocate
// per request buffer and avoid locking.
size_t random_access_max_buffer_size = 1024 * 1024;
// This is 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)
size_t writable_file_max_buffer_size = 1024 * 1024;
// Use 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
bool use_adaptive_mutex = false;
// Create DBOptions with default values for all fields
// Create DBOptions from Options
explicit DBOptions(const Options& options);
void Dump(Logger* log) const;
// 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
uint64_t bytes_per_sync = 0;
// Same as bytes_per_sync, but applies to WAL files
// Default: 0, turned off
uint64_t wal_bytes_per_sync = 0;
// A vector of EventListeners which callback functions will be called
// when specific RocksDB event happens.
std::vector<std::shared_ptr<EventListener>> listeners;
// If true, then the status of the threads involved in this DB will
// be tracked and available via GetThreadList() API.
// Default: false
bool enable_thread_tracking = false;
// The limited write rate to DB if soft_pending_compaction_bytes_limit or
// level0_slowdown_writes_trigger is triggered, or we are writing to the
// last mem table allowed and we allow more than 3 mem tables. It is
// calculated using size of user write requests before compression.
// RocksDB may decide to slow down more if the compaction still
// gets behind further.
// If the value is 0, we will infer a value from `rater_limiter` value
// if it is not empty, or 16MB if `rater_limiter` is empty. Note that
// if users change the rate in `rate_limiter` after DB is opened,
// `delayed_write_rate` won't be adjusted.
// Unit: byte per second.
// Default: 0
uint64_t delayed_write_rate = 0;
// 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
bool enable_pipelined_write = false;
// 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
bool allow_concurrent_memtable_write = true;
// 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
bool enable_write_thread_adaptive_yield = true;
// The maximum number of microseconds that a write operation will use
// a yielding spin loop to coordinate with other write threads before
// blocking on a mutex. (Assuming write_thread_slow_yield_usec is
// set properly) increasing this value is likely to increase RocksDB
// throughput at the expense of increased CPU usage.
// Default: 100
uint64_t write_thread_max_yield_usec = 100;
// The latency in microseconds after which a std::this_thread::yield
// call (sched_yield on Linux) is considered to be a signal that
// other processes or threads would like to use the current core.
// Increasing this makes writer threads more likely to take CPU
// by spinning, which will show up as an increase in the number of
// involuntary context switches.
// Default: 3
uint64_t write_thread_slow_yield_usec = 3;
// 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
bool skip_stats_update_on_db_open = false;
// Recovery mode to control the consistency while replaying WAL
// Default: kPointInTimeRecovery
WALRecoveryMode wal_recovery_mode = WALRecoveryMode::kPointInTimeRecovery;
// if set to false then recovery will fail when a prepared
// transaction is encountered in the WAL
bool allow_2pc = false;
// A global cache for table-level rows.
// Default: nullptr (disabled)
// Not supported in ROCKSDB_LITE mode!
std::shared_ptr<Cache> row_cache = nullptr;
// A filter object supplied to be invoked while processing write-ahead-logs
// (WALs) during recovery. The filter provides a way to inspect log
// records, ignoring a particular record or skipping replay.
// The filter is invoked at startup and is invoked from a single-thread
// currently.
WalFilter* wal_filter = nullptr;
#endif // ROCKSDB_LITE
// If true, then DB::Open / CreateColumnFamily / DropColumnFamily
// / SetOptions will fail if options file is not detected or properly
// persisted.
// DEFAULT: false
bool fail_if_options_file_error = false;
// If true, then print malloc stats together with rocksdb.stats
// when printing to LOG.
// DEFAULT: false
bool dump_malloc_stats = false;
// By default RocksDB replay WAL logs and flush them on DB open, which may
// create very small SST files. If this option is enabled, RocksDB will try
// to avoid (but not guarantee not to) flush during recovery. Also, existing
// WAL logs will be kept, so that if crash happened before flush, we still
// have logs to recover from.
// DEFAULT: false
bool avoid_flush_during_recovery = false;
// By default RocksDB will flush all memtables on DB close if there are
// unpersisted data (i.e. with WAL disabled) The flush can be skip to speedup
// DB close. Unpersisted data WILL BE LOST.
// DEFAULT: false
// Dynamically changeable through SetDBOptions() API.
bool avoid_flush_during_shutdown = false;
// Set this option to true during creation of database if you want
// to be able to ingest behind (call IngestExternalFile() skipping keys
// that already exist, rather than overwriting matching keys).
// Setting this option to true will affect 2 things:
// 1) Disable some internal optimizations around SST file compression
// 2) Reserve bottom-most level for ingested files only.
// 3) Note that num_levels should be >= 3 if this option is turned on.
// DEFAULT: false
// Immutable.
bool allow_ingest_behind = false;
// Needed to support differential snapshots.
// If set to true then DB will only process deletes with sequence number
// less than what was set by SetPreserveDeletesSequenceNumber(uint64_t ts).
// Clients are responsible to periodically call this method to advance
// the cutoff time. If this method is never called and preserve_deletes
// is set to true NO deletes will ever be processed.
// At the moment this only keeps normal deletes, SingleDeletes will
// not be preserved.
// DEFAULT: false
// Immutable (TODO: make it dynamically changeable)
bool preserve_deletes = false;
// If enabled it uses two queues for writes, one for the ones with
// disable_memtable and one for the ones that also write to memtable. This
// allows the memtable writes not to lag behind other writes. It can be used
// to optimize MySQL 2PC in which only the commits, which are serial, write to
// memtable.
bool two_write_queues = false;
// If true WAL is not flushed automatically after each write. Instead it
// relies on manual invocation of FlushWAL to write the WAL buffer to its
// file.
bool manual_wal_flush = false;
// Options to control the behavior of a database (passed to DB::Open)
struct Options : public DBOptions, public ColumnFamilyOptions {
// Create an Options object with default values for all fields.
Options() : DBOptions(), ColumnFamilyOptions() {}
Options(const DBOptions& db_options,
const ColumnFamilyOptions& column_family_options)
: DBOptions(db_options), ColumnFamilyOptions(column_family_options) {}
// The function recovers options to the option as in version 4.6.
Options* OldDefaults(int rocksdb_major_version = 4,
int rocksdb_minor_version = 6);
void Dump(Logger* log) const;
void DumpCFOptions(Logger* log) const;
// Some functions that make it easier to optimize RocksDB
// Set appropriate parameters for bulk loading.
// The reason that this is a function that returns "this" instead of a
// constructor is to enable chaining of multiple similar calls in the future.
// 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.
Options* PrepareForBulkLoad();
// Use this if your DB is very small (like under 1GB) and you don't want to
// spend lots of memory for memtables.
Options* OptimizeForSmallDb();
// An application can issue a read request (via Get/Iterators) and specify
// if that read should process data that ALREADY resides on a specified cache
// level. For example, if an application specifies kBlockCacheTier then the
// Get call will process data that is already processed in the memtable or
// the block cache. It will not page in data from the OS cache or data that
// resides in storage.
enum ReadTier {
kReadAllTier = 0x0, // data in memtable, block cache, OS cache or storage
kBlockCacheTier = 0x1, // data in memtable or block cache
kPersistedTier = 0x2, // persisted data. When WAL is disabled, this option
// will skip data in memtable.
// Note that this ReadTier currently only supports
// Get and MultiGet and does not support iterators.
kMemtableTier = 0x3 // data in memtable. used for memtable-only iterators.
// Options that control read operations
struct ReadOptions {
// If "snapshot" is non-nullptr, read as of the supplied snapshot
// (which must belong to the DB that is being read and which must
// not have been released). If "snapshot" is nullptr, use an implicit
// snapshot of the state at the beginning of this read operation.
// Default: nullptr
const Snapshot* snapshot;
// `iterate_lower_bound` defines the smallest key at which the backward
// iterator can return an entry. Once the bound is passed, Valid() will be
// false. `iterate_lower_bound` is inclusive ie the bound value is a valid
// entry.
// If prefix_extractor is not null, the Seek target and `iterate_lower_bound`
// need to have the same prefix. This is because ordering is not guaranteed
// outside of prefix domain.
// Default: nullptr
const Slice* iterate_lower_bound;
// "iterate_upper_bound" defines the extent upto which the forward iterator
// can returns entries. Once the bound is reached, Valid() will be false.
// "iterate_upper_bound" is exclusive ie the bound value is
// not a valid entry. If iterator_extractor is not null, the Seek target
// and iterate_upper_bound need to have the same prefix.
// This is because ordering is not guaranteed outside of prefix domain.
// Default: nullptr
const Slice* iterate_upper_bound;
// If non-zero, NewIterator will create a new table reader which
// performs reads of the given size. Using a large size (> 2MB) can
// improve the performance of forward iteration on spinning disks.
// Default: 0
size_t readahead_size;
// A threshold for the number of keys that can be skipped before failing an
// iterator seek as incomplete. The default value of 0 should be used to
// never fail a request as incomplete, even on skipping too many keys.
// Default: 0
uint64_t max_skippable_internal_keys;
// Specify if this read request should process data that ALREADY
// resides on a particular cache. If the required data is not
// found at the specified cache, then Status::Incomplete is returned.
// Default: kReadAllTier
ReadTier read_tier;
// If true, all data read from underlying storage will be
// verified against corresponding checksums.
// Default: true
bool verify_checksums;
// Should the "data block"/"index block"" read for this iteration be placed in
// block cache?
// Callers may wish to set this field to false for bulk scans.
// This would help not to the change eviction order of existing items in the
// block cache. Default: true
bool fill_cache;
// Specify to create a tailing iterator -- a special iterator that has a
// view of the complete database (i.e. it can also be used to read newly
// added data) and is optimized for sequential reads. It will return records
// that were inserted into the database after the creation of the iterator.
// Default: false
// Not supported in ROCKSDB_LITE mode!
bool tailing;
// Specify to create a managed iterator -- a special iterator that
// uses less resources by having the ability to free its underlying
// resources on request.
// Default: false
// Not supported in ROCKSDB_LITE mode!
bool managed;
// Enable a total order seek regardless of index format (e.g. hash index)
// used in the table. Some table format (e.g. plain table) may not support
// this option.
// If true when calling Get(), we also skip prefix bloom when reading from
// block based table. It provides a way to read existing data after
// changing implementation of prefix extractor.
bool total_order_seek;
// Enforce that the iterator only iterates over the same prefix as the seek.
// This option is effective only for prefix seeks, i.e. prefix_extractor is
// non-null for the column family and total_order_seek is false. Unlike
// iterate_upper_bound, prefix_same_as_start only works within a prefix
// but in both directions.
// Default: false
bool prefix_same_as_start;
// Keep the blocks loaded by the iterator pinned in memory as long as the
// iterator is not deleted, If used when reading from tables created with
// BlockBasedTableOptions::use_delta_encoding = false,
// Iterator's property "" is guaranteed to
// return 1.
// Default: false
bool pin_data;
// If true, when PurgeObsoleteFile is called in CleanupIteratorState, we
// schedule a background job in the flush job queue and delete obsolete files
// in background.
// Default: false
bool background_purge_on_iterator_cleanup;
// If true, keys deleted using the DeleteRange() API will be visible to
// readers until they are naturally deleted during compaction. This improves
// read performance in DBs with many range deletions.
// Default: false
bool ignore_range_deletions;
// A callback to determine whether relevant keys for this scan exist in a
// given table based on the table's properties. The callback is passed the
// properties of each table during iteration. If the callback returns false,
// the table will not be scanned. This option only affects Iterators and has
// no impact on point lookups.
// Default: empty (every table will be scanned)
std::function<bool(const TableProperties&)> table_filter;
// Needed to support differential snapshots. Has 2 effects:
// 1) Iterator will skip all internal keys with seqnum < iter_start_seqnum
// 2) if this param > 0 iterator will return INTERNAL keys instead of
// user keys; e.g. return tombstones as well.
// Default: 0 (don't filter by seqnum, return user keys)
SequenceNumber iter_start_seqnum;
ReadOptions(bool cksum, bool cache);
// Options that control write operations
struct WriteOptions {
// If true, the write will be flushed from the operating system
// buffer cache (by calling WritableFile::Sync()) before the write
// is considered complete. If this flag is true, writes will be
// slower.
// If this flag is false, and the machine crashes, some recent
// writes may be lost. Note that if it is just the process that
// crashes (i.e., the machine does not reboot), no writes will be
// lost even if sync==false.
// In other words, a DB write with sync==false has similar
// crash semantics as the "write()" system call. A DB write
// with sync==true has similar crash semantics to a "write()"
// system call followed by "fdatasync()".
// Default: false
bool sync;
// If true, writes will not first go to the write ahead log,
// and the write may got lost after a crash.
// Default: false
bool disableWAL;
// If true and if user is trying to write to column families that don't exist
// (they were dropped), ignore the write (don't return an error). If there
// are multiple writes in a WriteBatch, other writes will succeed.
// Default: false
bool ignore_missing_column_families;
// If true and we need to wait or sleep for the write request, fails
// immediately with Status::Incomplete().
// Default: false
bool no_slowdown;
// If true, this write request is of lower priority if compaction is
// behind. In this case, no_slowdown = true, the request will be cancelled
// immediately with Status::Incomplete() returned. Otherwise, it will be
// slowed down. The slowdown value is determined by RocksDB to guarantee
// it introduces minimum impacts to high priority writes.
// Default: false
bool low_pri;
: sync(false),
low_pri(false) {}
// Options that control flush operations
struct FlushOptions {
// If true, the flush will wait until the flush is done.
// Default: true
bool wait;
FlushOptions() : wait(true) {}
// Create a Logger from provided DBOptions
extern Status CreateLoggerFromOptions(const std::string& dbname,
const DBOptions& options,
std::shared_ptr<Logger>* logger);
// CompactionOptions are used in CompactFiles() call.
struct CompactionOptions {
// Compaction output compression type
// Default: snappy
CompressionType compression;
// Compaction will create files of size `output_file_size_limit`.
// Default: MAX, which means that compaction will create a single file
uint64_t output_file_size_limit;
// If > 0, it will replace the option in the DBOptions for this compaction.
uint32_t max_subcompactions;
: compression(kSnappyCompression),
max_subcompactions(0) {}
// For level based compaction, we can configure if we want to skip/force
// bottommost level compaction.
enum class BottommostLevelCompaction {
// Skip bottommost level compaction
// Only compact bottommost level if there is a compaction filter
// This is the default option
// Always compact bottommost level
// CompactRangeOptions is used by CompactRange() call.
struct CompactRangeOptions {
// If true, no other compaction will run at the same time as this
// manual compaction
bool exclusive_manual_compaction = true;
// If true, compacted files will be moved to the minimum level capable
// of holding the data or given level (specified non-negative target_level).
bool change_level = false;
// If change_level is true and target_level have non-negative value, compacted
// files will be moved to target_level.
int target_level = -1;
// Compaction outputs will be placed in options.db_paths[target_path_id].
// Behavior is undefined if target_path_id is out of range.
uint32_t target_path_id = 0;
// By default level based compaction will only compact the bottommost level
// if there is a compaction filter
BottommostLevelCompaction bottommost_level_compaction =
// If true, will execute immediately even if doing so would cause the DB to
// enter write stall mode. Otherwise, it'll sleep until load is low enough.
bool allow_write_stall = false;
// If > 0, it will replace the option in the DBOptions for this compaction.
uint32_t max_subcompactions = 0;
// IngestExternalFileOptions is used by IngestExternalFile()
struct IngestExternalFileOptions {
// Can be set to true to move the files instead of copying them.
bool move_files = false;
// If set to false, an ingested file keys could appear in existing snapshots
// that where created before the file was ingested.
bool snapshot_consistency = true;
// If set to false, IngestExternalFile() will fail if the file key range
// overlaps with existing keys or tombstones in the DB.
bool allow_global_seqno = true;
// If set to false and the file key range overlaps with the memtable key range
// (memtable flush required), IngestExternalFile will fail.
bool allow_blocking_flush = true;
// Set to true if you would like duplicate keys in the file being ingested
// to be skipped rather than overwriting existing data under that key.
// Usecase: back-fill of some historical data in the database without
// over-writing existing newer version of data.
// This option could only be used if the DB has been running
// with allow_ingest_behind=true since the dawn of time.
// All files will be ingested at the bottommost level with seqno=0.
bool ingest_behind = false;
} // namespace rocksdb