Extended SET VAR Optimizer Hint

Extended SET VAR Optimizer Hint

Percona Server for MySQL 8.0 extends the SET_VAR introduced in MySQL 8.0 effectively replacing the SET STATEMENT ... FOR statement. SET_VAR is an optimizer hint that can be applied to session variables.

Percona Server for MySQL 8.0 extends the SET_VAR hint to support the following:

  • The OPTIMIZE TABLE statement
  • MyISAM session variables
  • Plugin or Storage Engine variables
  • InnoDB Session variables
  • The ALTER TABLE statement
  • CALL stored_proc() statement
  • The ANALYZE TABLE statement
  • The CHECK TABLE statement
  • The LOAD INDEX statement (used for MyISAM)
  • The CREATE TABLE statement

Percona Server for MySQL 8.0 also supports setting the following variables by using SET_VAR:

  • innodb_lock_wait_timeout
  • innodb_tmpdir
  • innodb_ft_user_stopword_table
  • block_encryption_mode
  • histogram_generation_max_mem_size
  • myisam_sort_buffer_size
  • myisam_repair_threads
  • myisam_stats_method
  • preload_buffer_size (used by MyISAM only)

See also

MySQL Documentation: Variable-setting hint syntax
https://dev.mysql.com/doc/refman/8.0/en/optimizer-hints.html#optimizer-hints-set-var
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