# System Variable Differences Between MariaDB 5.5 and MySQL 5.5

The following is a comparison of variables that either appear only in [MariaDB 5.5](../../../../old-releases/release-notes-mariadb-5-5-series/changes-improvements-in-mariadb-5-5), or have different default settings in [MariaDB 5.5](https://app.gitbook.com/s/aEnK0ZXmUbJzqQrTjFyb/mariadb-community-server-release-notes/old-releases/release-notes-mariadb-5-5-series/changes-improvements-in-mariadb-5-5.md), and MySQL 5.5. MariaDB and MySQL 5.5.38, with only default plugins enabled, were used for the comparison.

The most notable differences are that MariaDB includes, by default, the [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria) storage engine, uses [Percona's XtraDB instead of Oracle's InnoDB](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/innodb), and has a different [thread pool implementation](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). For this reason, a default implementation of [MariaDB 5.5](../../../../old-releases/release-notes-mariadb-5-5-series/changes-improvements-in-mariadb-5-5) will use more memory than MySQL 5.5. This can be handled with the following rules of thumb:

* If you are not using [MyISAM](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine) and don't plan to use [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria):
  * Set [key\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_buffer_size) to something very low (16K) as it's not used.
  * Set [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) to what you think you need for handling internal tmp tables that didn't fit in memory.
  * Normally this is what before you had set for [key\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_buffer_size) (at least 1M).
* If you are using [MyISAM](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine) and not planning to use [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria):
  * Set [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) to what you think you need for handling internal tmp tables that didn't fit in memory.
* If you are planning to use [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria), you should set [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) to something that fits a big part of your normal data + overflow temporary tables.

The large number of differences between MySQL's and MariaDB's default innodb\* variables (based upon InnoDB/XtraDB differences) are not listed here. Details can be found on the [MariaDB versus MySQL - Compatibility](https://github.com/mariadb-corporation/docs-server/blob/test/release-notes/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference/README.md) page.

| Variable                                                                                                                                                                                            | [MariaDB 5.5](../../../../old-releases/release-notes-mariadb-5-5-series/changes-improvements-in-mariadb-5-5)                                 | MySQL 5.5                                            | Notes                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [aria\_block\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_block_size)                                                         | 8192                                                                                                                                         | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_checkpoint\_interval](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_checkpoint_interval)                                       | 30                                                                                                                                           | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_checkpoint\_log\_activity](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_checkpoint_log_activity)                              | 1048576                                                                                                                                      | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_force\_start\_after\_recovery\_failures](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_force_start_after_recovery_failures)    | 0                                                                                                                                            | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_group\_commit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_group_commit)                                                     | none                                                                                                                                         | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_group\_commit\_interval](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_group_commit_interval)                                  | 0                                                                                                                                            | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_log\_file\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_log_file_size)                                                  | 1073741824                                                                                                                                   | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_log\_purge\_type](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_log_purge_type)                                                | immediate                                                                                                                                    | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_max\_sort\_file\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_max_sort_file_size)                                       | 9223372036853727232                                                                                                                          | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_page\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_page_checksum)                                                   | ON                                                                                                                                           | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_pagecache\_age\_threshold](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_age_threshold)                              | 300                                                                                                                                          | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size)                                  | 134217720                                                                                                                                    | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_pagecache\_division\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_division_limit)                            | 100                                                                                                                                          | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_recover](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_recover)                                                                | NORMAL                                                                                                                                       | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_repair\_threads](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_repair_threads)                                                 | 1                                                                                                                                            | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_sort\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_sort_buffer_size)                                            | 134217728                                                                                                                                    | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_stats\_method](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_stats_method)                                                     | nulls-unequal                                                                                                                                | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_sync\_log\_dir](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_sync_log_dir)                                                    | NEWFILE                                                                                                                                      | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [aria\_used\_for\_temp\_tables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_used_for_temp_tables)                                   | ON                                                                                                                                           | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [binlog-annotate-row-events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/clients-and-utilities/logging-tools/mariadb-binlog/annotate_rows_log_event#master-option-binlog-annotate-row-events)    | OFF                                                                                                                                          | -                                                    | Introduced in [MariaDB 5.3](../../../../old-releases/release-notes-mariadb-5-3-series/changes-improvements-in-mariadb-5-3) for [replicating](https://github.com/mariadb-corporation/docs-server/blob/test/release-notes/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference/README.md) between [MariaDB 5.3](../../../../old-releases/release-notes-mariadb-5-3-series/changes-improvements-in-mariadb-5-3) and MySQL/[MariaDB 5.1](../../../../old-releases/release-notes-mariadb-5-1-series/changes-improvements-in-mariadb-5-1). |
| [binlog\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                              | NONE                                                                                                                                         | -                                                    | Specifies the type of BINLOG\_CHECKSUM\_ALG for log events in the [binary log](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/binary-log).                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| [binlog\_optimize\_thread\_scheduling](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                          | ON                                                                                                                                           | -                                                    | For optimized kernel thread scheduling.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| [deadlock\_search\_depth\_long](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_search_depth_long)                                  | 15                                                                                                                                           | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [deadlock\_search\_depth\_short](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_search_depth_short)                                | 4                                                                                                                                            | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [deadlock\_timeout\_long](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_timeout_long)                                             | 50000000                                                                                                                                     | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [deadlock\_timeout\_short](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_timeout_short)                                           | 10000                                                                                                                                        | -                                                    | The Aria storage engine is only available in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [debug\_no\_thread\_alarm](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#debug_no_thread_alarm)                                      | OFF                                                                                                                                          | -                                                    | Disable system thread alarm calls, for debugging or testing                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| [engine\_condition\_pushdown](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#engine_condition_pushdown)                               | OFF                                                                                                                                          | ON                                                   | Controlled by [optimizer\_switch](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#optimizer_switch)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [expensive\_subquery\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#expensive_subquery_limit)                                 | 100                                                                                                                                          | -                                                    | Used for determining expensive queries for optimization.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| [extra\_max\_connections](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables)     | 1                                                                                                                                            | -                                                    | Introduced in the [MariaDB 5.1 threadpool](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb-51-53).                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| [extra\_port](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables)                 | 0                                                                                                                                            | -                                                    | Introduced in the [MariaDB 5.1 threadpool](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb-51-53).                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| [ignore\_db\_dirs](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#ignore_db_dirs)                                                     |                                                                                                                                              | -                                                    | Comma-delimited list of directories in the data directory that are not considered as database directories. Only introduced in MySQL 5.6                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| [in\_transaction](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#in_transaction)                                                      | 0                                                                                                                                            | -                                                    | Set to 1 if you are in a transaction, and 0 if not.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| [join\_buffer\_space\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#join_buffer_space_limit)                                  | 2097152                                                                                                                                      | -                                                    | Maximum size in bytes of the query buffer. See [block-based join algorithms](https://app.gitbook.com/s/WCInJQ9cmGjq1lsTG91E/development-articles/mariadb-internals/mariadb-internals-documentation-query-optimizer/block-based-join-algorithms).                                                                                                                                                                                                                                                                                                                                                                                                               |
| [join\_cache\_level](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#join_cache_level)                                                 | 2                                                                                                                                            | -                                                    | For determining the join algorithms. See [block-based join algorithms](https://app.gitbook.com/s/WCInJQ9cmGjq1lsTG91E/development-articles/mariadb-internals/mariadb-internals-documentation-query-optimizer/block-based-join-algorithms).                                                                                                                                                                                                                                                                                                                                                                                                                     |
| [key\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_buffer_size)                                      | 134217728                                                                                                                                    | 8388608                                              | Size of the buffer for the index blocks used by MyISAM tables and shared for all threads.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| [key\_cache\_segments](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_cache_segments)                                | 0                                                                                                                                            | -                                                    | The number of segments in a key cache. See [Segmented Key Cache](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/system-variables/segmented-key-cache).                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| [log\_slow\_filter](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#log_slow_filter)                                                   | admin, filesort, filesort\_on\_disk, full\_join, full\_scan, query\_cache, query\_cache\_miss, tmp\_table, tmp\_table\_on\_disk              | -                                                    | For slow query log filtering.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| [log\_slow\_rate\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#log_slow_rate_limit)                                          | 1                                                                                                                                            | -                                                    | Limits the number of queries logged to the [slow query log](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/slow-query-log).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [log\_slow\_verbosity](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#log_slow_verbosity)                                             | ''                                                                                                                                           | -                                                    | Controls information to be added to the [slow query log](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/slow-query-log). See also [Slow Query Log Extended Statistics](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/query-optimizations/statistics-for-optimizing-queries/slow-query-log-extended-statistics).                                                                                                                                                                                                                                                           |
| [master\_verify\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                      | OFF                                                                                                                                          | -                                                    | Verify binlog checksums when reading events from the binlog on the master.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| [max\_seeks\_for\_key](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#max_seeks_for_key)                                              | 4294967295                                                                                                                                   | 4294967295 (32-bit) or 18446744073709547520 (64-bit) | The most key seeks required when searching with an index, regardless of the actual index cardinality. If this value is set lower than its default and maximum, indexes will tend to be preferred over table scans.                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| [max\_write\_lock\_count](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#max_write_lock_count)                                        | 4294967295                                                                                                                                   | 4294967295 (32-bit) or 18446744073709547520 (64-bit) | Read lock requests will be permitted for processing after this many write locks.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [mrr\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#mrr_buffer_size)                                                   | 262144                                                                                                                                       | -                                                    | Size of buffer to use when using multi-range read with range access. See [Multi Range Read optimization](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/mariadb-internal-optimizations/multi-range-read-optimization#range-access).                                                                                                                                                                                                                                                                                                                                                                                 |
| [myisam\_block\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#myisam_block_size)                                  | 1024                                                                                                                                         | -                                                    | Block size used for [MyISAM](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine) index pages.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| [myisam\_recover\_options](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#myisam_recover_options)                        | DEFAULT                                                                                                                                      | OFF                                                  | MyISAM recovery mode.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| new                                                                                                                                                                                                 | -                                                                                                                                            | OFF                                                  | Used for backward-compatibility with MySQL 4.1, not present in MariaDB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| [old\_mode](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#old_mode)                                                                  | Empty string                                                                                                                                 | -                                                    | Used for getting MariaDB to emulate behavior from an old version of MySQL or MariaDB. See [OLD Mode](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/old-mode).                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [optimizer\_switch](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#optimizer_switch)                                                  | [See details](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#optimizer_switch) |                                                      | A series of flags for controlling the query optimizer. MariaDB has introduced a number of new settings.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| [plugin\_maturity](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#plugin_maturity)                                                    | unknown                                                                                                                                      | -                                                    | Minimum acceptable plugin maturity.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| [progress\_report\_time](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#progress_report_time)                                         | 5                                                                                                                                            | -                                                    | See [Progress reporting](https://github.com/mariadb-corporation/docs-server/blob/test/release-notes/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference/README.md).                                                                                                                                                                                                                                                                                                                                                                 |
| [query\_cache\_strip\_comments](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#query_cache_strip_comments)                            | OFF                                                                                                                                          | -                                                    | Whether to strip any comments from the query before searching to see if it exists in the [query cache](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/query-cache).                                                                                                                                                                                                                                                                                                                                                                                                                      |
| [replicate\_annotate\_row\_events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                              | OFF                                                                                                                                          | -                                                    | Tells the slave to reproduce annotate\_rows\_events received from the master in its own binary log.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| [replicate\_do\_db](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                             | empty string                                                                                                                                 | -                                                    | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [replicate\_do\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                          | empty string                                                                                                                                 | -                                                    | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [replicate\_events\_marked\_for\_skip](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                          | replicate                                                                                                                                    | -                                                    | See [Selectively skipping replication of binlog events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/selectively-skipping-replication-of-binlog-events).                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| [replicate\_ignore\_db](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                         | empty string                                                                                                                                 | -                                                    | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [replicate\_ignore\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                      | empty string                                                                                                                                 | -                                                    | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [replicate\_wild\_do\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                    | empty string                                                                                                                                 | -                                                    | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [replicate\_wild\_ignore\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                | empty string                                                                                                                                 | -                                                    | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| [rowid\_merge\_buff\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#rowid_merge_buff_size)                                      | 8388608                                                                                                                                      | -                                                    | See [Non-semi-join subquery optimizations](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/query-optimizations/subquery-optimizations/non-semi-join-subquery-optimizations).                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| [skip\_replication](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                             | OFF                                                                                                                                          | -                                                    | See [Selectively skipping replication of binlog events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/selectively-skipping-replication-of-binlog-events).                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| [slave\_sql\_verify\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables)                                  | ON                                                                                                                                           | -                                                    | Verify binlog checksums when the slave SQL thread reads events from the relay log.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| [thread\_pool\_idle\_timeout](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 60                                                                                                                                           | -                                                    | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb).                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [thread\_pool\_max\_threads](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables)  | 60                                                                                                                                           | -                                                    | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb).                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [thread\_pool\_min\_threads](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables)  | 60                                                                                                                                           | -                                                    | Windows-only. See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb).                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| [thread\_pool\_oversubscribe](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 3                                                                                                                                            | -                                                    | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb).                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [thread\_pool\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables)          | Number of processors                                                                                                                         | 16\*                                                 | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). \*Only available in MySQL with a commercial plugin.                                                                                                                                                                                                                                                                                                                                                                                                       |
| [thread\_pool\_stall\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables)  | 500                                                                                                                                          | 6\*                                                  | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). \*Only available in MySQL with a commercial plugin.                                                                                                                                                                                                                                                                                                                                                                                                       |
| [thread\_stack](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#thread_stack)                                                          | 294912                                                                                                                                       | 196608 or 262144                                     | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb).                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| [userstat](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#userstat)                                                                   | OFF                                                                                                                                          | -                                                    | Whether to activate MariaDB's [User Statistics](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/query-optimizations/statistics-for-optimizing-queries/user-statistics) implementation, not available in MySQL.                                                                                                                                                                                                                                                                                                                                                                                                       |
| Variable                                                                                                                                                                                            | [MariaDB 5.5](../../../../old-releases/release-notes-mariadb-5-5-series/changes-improvements-in-mariadb-5-5)                                 | MySQL 5.5                                            | Notes                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |

## See Also

* [System Variable Differences Between MariaDB 10.1 and MySQL 5.7](system-variable-differences-between-mariadb-10-1-and-mysql-5-7)
* [System Variable Differences Between MariaDB 10.1 and MySQL 5.6](system-variable-differences-between-mariadb-10-1-and-mysql-5-6)
* [System Variable Differences Between MariaDB 10.0 and MySQL 5.6](system-variable-differences-between-mariadb-100-and-mysql-56)

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