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TokuDB Variables

Like all storage engines, TokuDB has variables to tune performance and control behavior. Fractal Tree algorithms are designed for near optimal performance and TokuDB’s default settings should work well in most situations, eliminating the need for complex and time consuming tuning in most cases.

TokuDB Server Variables

Name Cmd-Line Option File Var Scope Dynamic
tokudb_alter_print_error Yes Yes Session, Global Yes
tokudb_analyze_delete_fraction Yes Yes Session, Global Yes
tokudb_analyze_in_background Yes Yes Session, Global Yes
tokudb_analyze_mode Yes Yes Session, Global Yes
tokudb_analyze_throttle Yes Yes Session, Global Yes
tokudb_analyze_time Yes Yes Session, Global Yes
tokudb_auto_analyze Yes Yes Session, Global Yes
tokudb_backup_allowed_prefix No Yes Global No
tokudb_backup_dir No Yes Session No
tokudb_backup_exclude Yes Yes Session, Global Yes
tokudb_backup_last_error Yes Yes Session, Global Yes
tokudb_backup_last_error_string Yes Yes Session, Global Yes
tokudb_backup_plugin_version No No Global No
tokudb_backup_throttle Yes Yes Session, Global Yes
tokudb_backup_version No No Global No
tokudb_block_size Yes Yes Session, Global Yes
tokudb_bulk_fetch Yes Yes Session, Global Yes
tokudb_cachetable_pool_threads Yes Yes Global No
tokudb_cardinality_scale_percent Yes Yes Global Yes
tokudb_check_jemalloc Yes Yes Global No
tokudb_checkpoint_lock Yes Yes Global No
tokudb_checkpoint_on_flush_logs Yes Yes Global Yes
tokudb_checkpoint_pool_threads Yes Yes Global Yes
tokudb_checkpointing_period Yes Yes Global Yes
tokudb_cleaner_iterations Yes Yes Global Yes
tokudb_cleaner_period Yes Yes Global Yes
tokudb_client_pool_threads Yes Yes Global No
tokudb_commit_sync Yes Yes Session, Global Yes
tokudb_compress_buffers_before_eviction Yes Yes Global No
tokudb_create_index_online Yes Yes Session, Global Yes
tokudb_data_dir Yes Yes Global No
tokudb_debug Yes Yes Global Yes
tokudb_dir_per_db Yes Yes Global Yes
tokudb_directio Yes Yes Global No
tokudb_disable_hot_alter Yes Yes Session, Global Yes
tokudb_disable_prefetching Yes Yes Session, Global Yes
tokudb_disable_slow_alter Yes Yes Session, Global Yes
tokudb_empty_scan Yes Yes Session, Global Yes
tokudb_enable_fast_update Yes Yes Session, Global Yes
tokudb_enable_fast_upsert Yes Yes Session, Global Yes
tokudb_enable_partial_eviction Yes Yes Global No
tokudb_fanout Yes Yes Session, Global Yes
tokudb_fs_reserve_percent Yes Yes Global No
tokudb_fsync_log_period Yes Yes Global Yes
tokudb_hide_default_row_format Yes Yes Session, Global Yes
tokudb_killed_time Yes Yes Session, Global Yes
tokudb_last_lock_timeout Yes Yes Session, Global Yes
tokudb_load_save_space Yes Yes Session, Global Yes
tokudb_loader_memory_size Yes Yes Session, Global Yes
tokudb_lock_timeout Yes Yes Session, Global Yes
tokudb_lock_timeout_debug Yes Yes Session, Global Yes
tokudb_log_dir Yes Yes Global No
tokudb_max_lock_memory Yes Yes Global No
tokudb_optimize_index_fraction Yes Yes Session, Global Yes
tokudb_optimize_index_name Yes Yes Session, Global Yes
tokudb_optimize_throttle Yes Yes Session, Global Yes
tokudb_pk_insert_mode Yes Yes Session, Global Yes
tokudb_prelock_empty Yes Yes Session, Global Yes
tokudb_read_block_size Yes Yes Session, Global Yes
tokudb_read_buf_size Yes Yes Session, Global Yes
tokudb_read_status_frequency Yes Yes Global Yes
tokudb_row_format Yes Yes Session, Global Yes
tokudb_rpl_check_readonly Yes Yes Session, Global Yes
tokudb_rpl_lookup_rows Yes Yes Session, Global Yes
tokudb_rpl_lookup_rows_delay Yes Yes Session, Global Yes
tokudb_rpl_unique_checks Yes Yes Session, Global Yes
tokudb_rpl_unique_checks_delay Yes Yes Session, Global Yes
tokudb_strip_frm_data Yes Yes Global No
tokudb_support_xa Yes Yes Session, Global Yes
tokudb_tmp_dir Yes Yes Global No
tokudb_version No No Global No
tokudb_write_status_frequency Yes Yes Global Yes

tokudb_alter_print_error

Option Description
Command-line Yes
Config file Yes
Scope Global/Session
Dynamic Yes
Data type Boolean
Default OFF

When set to ON errors will be printed to the client during the ALTER TABLE operations on TokuDB tables.

tokudb_analyze_delete_fraction

Option Description
Command-line Yes
Config file Yes
Scope Global/Session
Dynamic Yes
Data type Numeric
Default 1.000000
Range 0.0 - 1.000000

This variables controls whether or not deleted rows in the fractal tree are reported to the client and to the MySQL error log during an ANALYZE TABLE operation on a TokuDB table. When set to 1, nothing is reported. When set to 0.1 and at least 10% of the rows scanned by ANALYZE were deleted rows that are not yet garbage collected, a report is returned to the client and the MySQL error log.

tokudb_backup_allowed_prefix

Option Description
Command-line No
Config file Yes
Scope Global
Dynamic No
Data type String
Default NULL

This system-level variable restricts the location of the destination directory where the backups can be located. Attempts to backup to a location outside of the directory this variable points to or its children will result in an error.

The default is NULL, backups have no restricted locations. This read only variable can be set in the my.cnf configuration file and displayed with the SHOW VARIABLES command when Percona TokuBackup plugin is loaded.

mysql> SHOW VARIABLES LIKE 'tokudb_backup_allowed_prefix';

The output could be:

+------------------------------+-----------+
| Variable_name                | Value     |
+------------------------------+-----------+
| tokudb_backup_allowed_prefix | /dumpdir  |
+------------------------------+-----------+

tokudb_backup_dir

Option Description
Command-line No
Config file No
Scope Session
Dynamic Yes
Data type String
Default NULL

When enabled, this session level variable serves two purposes, to point to the destination directory where the backups will be dumped and to kick off the backup as soon as it is set. For more information see Percona TokuBackup.

tokudb_backup_exclude

Option Description
Command-line No
Config file No
Scope Session
Dynamic Yes
Data type String
Default (mysqld_safe.pid)+

Use this variable to set a regular expression that defines source files excluded from backup. For example, to exclude all lost+found directories, use the following command:

mysqlset tokudb_backup_exclude='/lost\\+found(#|/)';

For more information see Percona TokuBackup.

tokudb_backup_last_error

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 0

This session variable will contain the error number from the last backup. 0 indicates success. For more information see Percona TokuBackup.

tokudb_backup_last_error_string

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type String
Default NULL

This session variable will contain the error string from the last backup. For more information see Percona TokuBackup.

tokudb_backup_plugin_version

Option Description
Command-line No
Config file No
Scope Global
Dynamic No
Data type String

This read-only server variable documents the version of the TokuBackup plugin. For more information see Percona TokuBackup.

tokudb_backup_throttle

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 18446744073709551615

This variable specifies the maximum number of bytes per second the copier of a hot backup process will consume. Lowering its value will cause the hot backup operation to take more time but consume less I/O on the server. The default value is 18446744073709551615 which means no throttling. For more information see Percona TokuBackup.

tokudb_backup_version

Option Description
Command-line No
Config file No
Scope Global
Dynamic No
Data type String

This read-only server variable documents the version of the hot backup library. For more information see Percona TokuBackup.

tokudb_block_size

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 4194304
Range 4096 - 4294967295

This variable controls the maximum size of node in memory before messages must be flushed or node must be split.

Changing the value of tokudb_block_size only affects subsequently created tables and indexes. The value of this variable cannot be changed for an existing table/index without a dump and reload.

tokudb_bulk_fetch

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

This variable determines if our bulk fetch algorithm is used for SELECT statements. SELECT statements include pure SELECT ... statements, as well as INSERT INTO table-name ... SELECT ..., CREATE TABLE table-name ... SELECT ..., REPLACE INTO table-name ... SELECT ..., INSERT IGNORE INTO table-name ... SELECT ..., and INSERT INTO table-name ... SELECT ... ON DUPLICATE KEY UPDATE.

tokudb_cache_size

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Numeric

This variable configures the size in bytes of the TokuDB cache table. The default cache table size is ½ of physical memory. Percona highly recommends using the default setting if using buffered I/O, if using direct I/O then consider setting this parameter to 80% of available memory.

Consider decreasing tokudb_cache_size if excessive swapping is causing performance problems. Swapping may occur when running multiple MySQL server instances or if other running applications use large amounts of physical memory.

tokudb_cachetable_pool_threads

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 0
Range 0 - 1024

This variable defines the number of threads for the cachetable worker thread pool. This pool is used to perform node prefetches, and to serialize, compress, and write nodes during cachetable eviction. The default value of 0 calculates the pool size to be num_cpu_threads * 2.

tokudb_check_jemalloc

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Boolean
Default ON

This variable enables/disables startup checking if jemalloc is linked and correct version and that transparent huge pages are disabled. Used for testing only.

tokudb_checkpoint_lock

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default OFF

Disables checkpointing when true. Session variable but acts like a global, any session disabling checkpointing disables it globally. If a session sets this lock and disconnects or terminates for any reason, the lock will not be released. Special purpose only, do not use this in your application.

tokudb_checkpoint_on_flush_logs

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Boolean
Default OFF

When enabled forces a checkpoint if we get a flush logs command from the server.

tokudb_checkpoint_pool_threads

Option Description
Command-line Yes
Config file Yes
Scope
Dynamic No
Data type Numeric
Default 0
Range 0 - 1024

This defines the number of threads for the checkpoint worker thread pool. This pool is used to serialize, compress and write nodes cloned during checkpoint. Default of 0 uses old algorithm to set pool size to num_cpu_threads/4.

tokudb_checkpointing_period

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 60
Range 0 - 4294967295

This variable specifies the time in seconds between the beginning of one checkpoint and the beginning of the next. The default time between TokuDB checkpoints is 60 seconds. We recommend leaving this variable unchanged.

tokudb_cleaner_iterations

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 5
Range 0 - 18446744073709551615

This variable specifies how many internal nodes get processed in each tokudb_cleaner_period period. The default value is 5. Setting this variable to 0 turns off cleaner threads.

tokudb_cleaner_period

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 1
Range 0 - 18446744073709551615

This variable specifies how often in seconds the cleaner thread runs. The default value is 1. Setting this variable to 0 turns off cleaner threads.

tokudb_client_pool_threads

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Numeric
Default 0
Range 0 - 1024

This variable defines the number of threads for the client operations thread pool. This pool is used to perform node maintenance on over/undersized nodes such as message flushing down the tree, node splits, and node merges. Default of 0 uses old algorithm to set pool size to 1 \* num_cpu_threads.

tokudb_commit_sync

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

Session variable tokudb_commit_sync controls whether or not the transaction log is flushed when a transaction commits. The default behavior is that the transaction log is flushed by the commit. Flushing the transaction log requires a disk write and may adversely affect the performance of your application.

To disable synchronous flushing of the transaction log, disable the tokudb_commit_sync session variable as follows:

SET tokudb_commit_sync=OFF;

Disabling this variable may make the system run faster. However, transactions committed since the last checkpoint are not guaranteed to survive a crash.

Warning

By disabling this variable and/or setting the tokudb_fsync_log_period to non-zero value you have effectively downgraded the durability of the storage engine. If you were to have a crash in this same window, you would lose data. The same issue would also appear if you were using some kind of volume snapshot for backups.

tokudb_compress_buffers_before_eviction

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Boolean
Default ON

When this variable is enabled it allows the evictor to compress unused internal node partitions in order to reduce memory requirements as a first step of partial eviction before fully evicting the partition and eventually the entire node.

tokudb_create_index_online

This variable controls whether indexes created with the CREATE INDEX command are hot (if enabled), or offline (if disabled). Hot index creation means that the table is available for inserts and queries while the index is being created. Offline index creation means that the table is not available for inserts and queries while the index is being created.

Note

Hot index creation is slower than offline index creation.

tokudb_data_dir

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type String
Default NULL

This variable configures the directory name where the TokuDB tables are stored. The default value is NULL which uses the location of the MySQL data directory. For more information check TokuDB files and file types and TokuDB file management.

tokudb_debug

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 0
Range 0 - 18446744073709551615

This variable enables mysqld debug printing to STDERR for TokuDB. Produces tremendous amounts of output that is nearly useless to anyone but a TokuDB developer, not recommended for any production use at all. It is a mask value ULONG:

#define TOKUDB_DEBUG_INIT                   (1<<0)
#define TOKUDB_DEBUG_OPEN                   (1<<1)
#define TOKUDB_DEBUG_ENTER                  (1<<2)
#define TOKUDB_DEBUG_RETURN                 (1<<3)
#define TOKUDB_DEBUG_ERROR                  (1<<4)
#define TOKUDB_DEBUG_TXN                    (1<<5)
#define TOKUDB_DEBUG_AUTO_INCREMENT         (1<<6)
#define TOKUDB_DEBUG_INDEX_KEY              (1<<7)
#define TOKUDB_DEBUG_LOCK                   (1<<8)
#define TOKUDB_DEBUG_CHECK_KEY              (1<<9)
#define TOKUDB_DEBUG_HIDE_DDL_LOCK_ERRORS   (1<<10)
#define TOKUDB_DEBUG_ALTER_TABLE            (1<<11)
#define TOKUDB_DEBUG_UPSERT                 (1<<12)
#define TOKUDB_DEBUG_CHECK                  (1<<13)
#define TOKUDB_DEBUG_ANALYZE                (1<<14)
#define TOKUDB_DEBUG_XA                     (1<<15)
#define TOKUDB_DEBUG_SHARE                  (1<<16)

tokudb_dir_per_db

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Boolean
Default ON

The variable has been implemented in Percona Server for MySQL 5.7.15-9. When this variable is set to ON all new tables and indices will be placed within their corresponding database directory within the tokudb_data_dir or system source/glossary.rst`datadir`. Existing table files will not be automatically relocated to their corresponding database directory. If you rename a table, while this variable is enabled, the mapping in the Percona FT directory file will be updated and the files will be renamed on disk to reflect the new table name. For more information check TokuDB files and file types and TokuDB file management.

tokudb_directio

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Boolean
Default OFF

When enabled, TokuDB employs Direct I/O rather than Buffered I/O for writes. When using Direct I/O, consider increasing tokudb_cache_size from its default of ½ physical memory.

tokudb_disable_hot_alter

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default OFF

This variable is used specifically for testing or to disable hot alter in case there are bugs. Not for use in production.

tokudb_disable_prefetching

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default OFF

TokuDB attempts to aggressively prefetch additional blocks of rows, which is helpful for most range queries but may create unnecessary I/O for range queries with LIMIT clauses. Prefetching is ON by default, with a value of 0, it can be disabled by setting this variable to 1.

tokudb_disable_slow_alter

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default OFF

This variable is used specifically for testing or to disable hot alter in case there are bugs. Not for use in production. It controls whether slow alter tables are allowed. For example, the following command is slow because HCADER does not allow a mixture of column additions, deletions, or expansions:

ALTER TABLE table
ADD COLUMN column_a INT,
DROP COLUMN column_b;

By default, tokudb_disable_slow_alter is disabled, and the engine reports back to MySQL that this is unsupported resulting in the following output:

ERROR 1112 (42000): Table 'test_slow' uses an extension that doesn't exist in this MySQL version

tokudb_empty_scan

Defines direction to be used to perform table scan to check for empty tables for bulk loader.

tokudb_enable_fast_update

Option Description
Command-line Yes
Config file Yes
Scope Global/Session
Dynamic Yes
Data type Boolean
Default OFF

Toggles the fast updates feature ON/OFF for the UPDATE statement. Fast update involves queries optimization to avoid random reads during their execution.

tokudb_enable_fast_upsert

Option Description
Command-line Yes
Config file Yes
Scope Global/Session
Dynamic Yes
Data type Boolean
Default OFF

Toggles the fast updates feature ON/OFF for the INSERT statement. Fast update involves queries optimization to avoid random reads during their execution.

tokudb_enable_partial_eviction

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Boolean
Default ON

This variable is used to control if partial eviction of nodes is enabled or disabled.

tokudb_fanout

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 16
Range 2-16384

This variable controls the Fractal Tree fanout. The fanout defines the number of pivate keys or child nodes for each internal tree node. Changing the value of tokudb_fanout only affects subsequently created tables and indexes. The value of this variable cannot be changed for an existing table/index without a dump and reload.

tokudb_fs_reserve_percent

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Numeric
Default 5
Range 0-100

This variable controls the percentage of the file system that must be available for inserts to be allowed. By default, this is set to 5. We recommend that this reserve be at least half the size of your physical memory. See Full Disks for more information.

tokudb_fsync_log_period

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 0
Range 0-4294967295

This variable controls the frequency, in milliseconds, for fsync() operations. If set to 0 then the fsync() behavior is only controlled by the tokudb_commit_sync, which can be ON or OFF.

tokudb_hide_default_row_format

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

This variable is used to hide the ROW_FORMAT in SHOW CREATE TABLE. If zlib compression is used, row format will show as DEFAULT.

tokudb_killed_time

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 4000
Range 0-18446744073709551615

This variable is used to specify frequency in milliseconds for lock wait to check to see if the lock was killed.

tokudb_last_lock_timeout

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type String
Default NULL

This variable contains a JSON document that describes the last lock conflict seen by the current MySQL client. It gets set when a blocked lock request times out or a lock deadlock is detected.

The tokudb_lock_timeout_debug session variable must have bit 0 set for this behavior, otherwise this session variable will be empty.

tokudb_load_save_space

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

This session variable changes the behavior of the bulk loader. When it is disabled the bulk loader stores intermediate data using uncompressed files (which consumes additional CPU), whereas ON compresses the intermediate files.

Note

The location of the temporary disk space used by the bulk loader may be specified with the tokudb_tmp_dir server variable.

If a LOAD DATA INFILE statement fails with the error message ERROR 1030 (HY000): Got error 1 from storage engine, then there may not be enough disk space for the optimized loader, so disable tokudb_prelock_empty and try again. More information is available in Known Issues.

tokudb_loader_memory_size

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 100000000
Range 0-18446744073709551615

This variable limits the amount of memory (in bytes) that the TokuDB bulk loader will use for each loader instance. Increasing this value may provide a performance benefit when loading extremely large tables with several secondary indexes.

Note

Memory allocated to a loader is taken from the TokuDB cache, defined in tokudb_cache_size, and may impact the running workload’s performance as existing cached data must be ejected for the loader to begin.

tokudb_lock_timeout

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 4000
Range 0-18446744073709551615

This variable controls the amount of time that a transaction will wait for a lock held by another transaction to be released. If the conflicting transaction does not release the lock within the lock timeout, the transaction that was waiting for the lock will get a lock timeout error. The units are milliseconds. A value of 0 disables lock waits. The default value is 4000 (four seconds).

If your application gets a lock wait timeout error (-30994), then you may find that increasing the tokudb_lock_timeout may help. If your application gets a deadlock found error (-30995), then you need to abort the current transaction and retry it.

tokudb_lock_timeout_debug

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 1
Range 0-3

The following values are available:

  • 0: No lock timeouts or lock deadlocks are reported.

  • 1: A JSON document that describes the lock conflict is stored in the tokudb_last_lock_timeout session variable

  • 2: A JSON document that describes the lock conflict is printed to the MySQL error log.

In addition to the JSON document describing the lock conflict, the following lines are printed to the MySQL error log:

* A line containing the blocked thread id and blocked SQL

* A line containing the blocking thread id and the blocking SQL.

* `3`: A JSON document that describes the lock conflict is stored in the

tokudb_last_lock_timeout session variable and is printed to the MySQL error log.

In addition to the JSON document describing the lock conflict, the following lines are printed to the MySQL error log:

* A line containing the blocked thread id and blocked SQL


* A line containing the blocking thread id and the blocking SQL.

tokudb_log_dir

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type String
Default NULL

This variable specifies the directory where the TokuDB log files are stored. The default value is NULL which uses the location of the MySQL data directory. Configuring a separate log directory is somewhat involved. Please contact Percona support for more details. For more information check TokuDB files and file types and TokuDB file management.

Warning

After changing TokuDB log directory path, the old TokuDB recovery log file should be moved to new directory prior to start of MySQL server and log file’s owner must be the mysql user. Otherwise server will fail to initialize the TokuDB store engine restart.

tokudb_max_lock_memory

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type Numeric
Default 65560320
Range 0-18446744073709551615

This variable specifies the maximum amount of memory for the PerconaFT lock table.

tokudb_optimize_index_fraction

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 1.000000
Range 0.000000 - 1.000000

For patterns where the left side of the tree has many deletions (a common pattern with increasing id or date values), it may be useful to delete a percentage of the tree. In this case, it’s possible to optimize a subset of a fractal tree starting at the left side. The tokudb_optimize_index_fraction session variable controls the size of the sub tree. Valid values are in the range [0.0,1.0] with default 1.0 (optimize the whole tree).

tokudb_optimize_index_name

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type String
Default NULL

This variable can be used to optimize a single index in a table, it can be set to select the index by name.

tokudb_optimize_throttle

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 0
Range 0-18446744073709551615

By default, table optimization will run with all available resources. To limit the amount of resources, it is possible to limit the speed of table optimization. This determines an upper bound on how many fractal tree leaf nodes per second are optimized. The default 0 imposes no limit.

tokudb_pk_insert_mode

Removed in Percona Server for MySQL 5.7.12-5.

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 1
Range 0-3

Note

The tokudb_pk_insert_mode session variable has been removed in Percona Server for MySQL Percona Server for MySQL 5.7.12-5 and the behavior is now that of the former tokudb_pk_insert_mode set to 1. The optimization will be used where safe and not used where not safe.

tokudb_prelock_empty

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

By default TokuDB preemptively grabs an entire table lock on empty tables. If one transaction is doing the loading, such as when the user is doing a table load into an empty table, this default provides a considerable speedup.

However, if multiple transactions try to do concurrent operations on an empty table, all but one transaction will be locked out. Disabling tokudb_prelock_empty optimizes for this multi-transaction case by turning off preemptive pre-locking.

Note

If this variable is set to OFF, fast bulk loading is turned off as well.

tokudb_read_block_size

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 65536 (64KB)
Range 4096 - 4294967295

Fractal tree leaves are subdivided into read blocks, in order to speed up point queries. This variable controls the target uncompressed size of the read blocks. The units are bytes and the default is 65,536 (64 KB). A smaller value favors read performance for point and small range scans over large range scans and higher compression. The minimum value of this variable is 4096.

Changing the value of tokudb_read_block_size only affects subsequently created tables. The value of this variable cannot be changed for an existing table without a dump and reload.

tokudb_read_buf_size

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 131072 (128KB)
Range 0 - 1048576

This variable controls the size of the buffer used to store values that are bulk fetched as part of a large range query. Its unit is bytes and its default value is 131,072 (128 KB).

A value of 0 turns off bulk fetching. Each client keeps a thread of this size, so it should be lowered if situations where there are a large number of clients simultaneously querying a table.

tokudb_read_status_frequency

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 10000
Range 0 - 4294967295

This variable controls in how many reads the progress is measured to display SHOW PROCESSLIST. Reads are defined as SELECT queries.

For slow queries, it can be helpful to set this variable and tokudb_write_status_frequency to 1, and then run SHOW PROCESSLIST several times to understand what progress is being made.

tokudb_row_format

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type ENUM
Default TOKUDB_ZLIB
Range TOKUDB_DEFAULT, TOKUDB_FAST, TOKUDB_SMALL, TOKUDB_ZLIB, TOKUDB_QUICKLZ, TOKUDB_LZMA, TOKUDB_SNAPPY, TOKUDB_UNCOMPRESSED

This controls the default compression algorithm used to compress data when no row format is specified in the CREATE TABLE command. For more information on compression algorithms see Compression Details.

tokudb_rpl_check_readonly

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

The TokuDB replication code will run row events from the binary log with Read Free Replication when the replica is in read-only mode. This variable is used to disable the replica read only check in the TokuDB replication code.

This allows Read-Free-Replication to run when the replica is NOT read-only. By default, tokudb_rpl_check_readonly is enabled (check that replica is read-only). Do NOT change this value unless you completely understand the implications!

tokudb_rpl_lookup_rows

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

When disabled, TokuDB replication replicas skip row lookups for delete row log events and update row log events, which eliminates all associated read I/O for these operations.

Warning

TokuDB Read Free Replication will not propagate UPDATE and DELETE events reliably if TokuDB table is missing the primary key which will eventually lead to data inconsistency on the replica.

Note

Optimization is only enabled when read_only is set to 1 and binlog_format is ROW.

tokudb_rpl_lookup_rows_delay

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 0
Range 0 - 18446744073709551615

This variable allows for simulation of long disk reads by sleeping for the given number of microseconds prior to the row lookup query, it should only be set to a non-zero value for testing.

tokudb_rpl_unique_checks

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

When disabled, TokuDB replication replicas skip uniqueness checks on inserts and updates, which eliminates all associated read I/O for these operations.

Note

Optimization is only enabled when read_only is set to 1 and binlog_format is ROW.

tokudb_rpl_unique_checks_delay

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Numeric
Default 0
Range 0 - 18446744073709551615

This variable allows for simulation of long disk reads by sleeping for the given number of microseconds prior to the row lookup query, it should only be set to a non-zero value for testing.

tokudb_strip_frm_data

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Boolean
Default OFF

When this variable is set to ON during the startup server will check all the status files and remove the embedded .frm metadata. This variable can be used to assist in TokuDB data recovery.

Warning

Use this variable only if you know what you’re doing otherwise it could lead to data loss.

tokudb_support_xa

Option Description
Command-line Yes
Config file Yes
Scope Session, Global
Dynamic Yes
Data type Boolean
Default ON

This variable defines whether or not the prepare phase of an XA transaction performs an fsync().

tokudb_tmp_dir

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic No
Data type String

This variable specifies the directory where the TokuDB bulk loader stores temporary files. The bulk loader can create large temporary files while it is loading a table, so putting these temporary files on a disk separate from the data directory can be useful.

tokudb_load_save_space determines whether the data is compressed or not. The error message ERROR 1030 (HY000): Got error 1 from storage engine could indicate that the disk has run out of space.

For example, it can make sense to use a high-performance disk for the data directory and a very inexpensive disk for the temporary directory. The default location for temporary files is the MySQL data directory.

For more information check TokuDB files and file types and TokuDB file management.

tokudb_version

Option Description
Command-line No
Config file No
Scope Global
Dynamic No
Data type String

This read-only variable documents the version of the TokuDB storage engine.

tokudb_write_status_frequency

Option Description
Command-line Yes
Config file Yes
Scope Global
Dynamic Yes
Data type Numeric
Default 1000
Range 0 - 4294967295

This variable controls in how many writes the progress is measured to display SHOW PROCESSLIST. Writes are defined as INSERT, UPDATE and DELETE queries.

For slow queries, it can be helpful to set this variable and tokudb_read_status_frequency to 1, and then run SHOW PROCESSLIST several times to understand what progress is being made.