Parallel hint in MARIADB

In MariaDB, the PARALLEL hint, similar to MySQL, isn't directly available. MariaDB also relies on its query optimizer to determine whether to execute a query in parallel based on various factors like system resources, table sizes, and query complexity.

However, MariaDB does provide some configuration options that can indirectly influence parallelism, particularly for certain types of operations like backups and restores.

One such option is myisam-recover-options, which can be used to specify the number of concurrent threads for repairing MyISAM tables. Increasing the value of this option can lead to parallel repair operations when dealing with multiple MyISAM tables.

Here's how you can configure myisam-recover-options to enable parallel repair operations in MariaDB:

SET GLOBAL myisam-recover-options='BACKUP,FORCE';

In this example:

- BACKUP specifies that the MyISAM storage engine should perform automatic crash recovery on startup to ensure table consistency.

- FORCE indicates that even if MariaDB detects a crashed table, it should attempt to repair it without asking for confirmation.

While this setting isn't a direct parallel execution hint for general queries, it can facilitate parallelism for specific maintenance operations involving MyISAM tables.

For more general-purpose parallelism, MariaDB also provides system variables like aria-page-cache-buffer-size, innodb-read-io-threads, and innodb-write-io-threads that can be adjusted to improve parallelism for certain types of I/O-bound operations.

Keep in mind that the effectiveness of parallelism in MariaDB, as in MySQL, heavily depends on factors such as workload characteristics and available system resources. Additionally, MariaDB's query optimizer decides whether to use parallel execution for queries based on its internal heuristics, and there's no direct query hint available for influencing this decision.