Syntax

optimizer_switch_on()
optimizer_switch_off()
optimizer_switch_choice("on" | "off")

Description

The above procedures can be used to check which optimizer_switch options are on or off. The result set is sorted according to optimizer_switch option name.

Example

select @@optimizer_switch\G
*************************** 1. row ***************************
index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,
index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,
derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,
in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,
subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,
semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,
optimize_join_buffer_size=on,table_elimination=on,extended_keys=on,exists_to_in=on,
orderby_uses_equalities=on,condition_pushdown_for_derived=on,split_materialized=on,
condition_pushdown_for_subquery=on,rowid_filter=on,condition_pushdown_from_having=on,
not_null_range_scan=off

call sys.optimizer_switch_on();
+---------------------------------+------+
| option                          | opt  |
+---------------------------------+------+
| condition_pushdown_for_derived  | on   |
| condition_pushdown_for_subquery | on   |
| condition_pushdown_from_having  | on   |
| derived_merge                   | on   |
| derived_with_keys               | on   |
| exists_to_in                    | on   |
| extended_keys                   | on   |
| firstmatch                      | on   |
| index_condition_pushdown        | on   |
| index_merge                     | on   |
| index_merge_intersection        | on   |
| index_merge_sort_union          | on   |
| index_merge_union               | on   |
| in_to_exists                    | on   |
| join_cache_bka                  | on   |
| join_cache_hashed               | on   |
| join_cache_incremental          | on   |
| loosescan                       | on   |
| materialization                 | on   |
| optimize_join_buffer_size       | on   |
| orderby_uses_equalities         | on   |
| outer_join_with_cache           | on   |
| partial_match_rowid_merge       | on   |
| partial_match_table_scan        | on   |
| rowid_filter                    | on   |
| semijoin                        | on   |
| semijoin_with_cache             | on   |
| split_materialized              | on   |
| subquery_cache                  | on   |
| table_elimination               | on   |
+---------------------------------+------+


call sys.optimizer_switch_off();
+-------------------------------+------+
| option                        | opt  |
+-------------------------------+------+
| engine_condition_pushdown     | off  |
| index_merge_sort_intersection | off  |
| mrr                           | off  |
| mrr_cost_based                | off  |
| mrr_sort_keys                 | off  |
| not_null_range_scan           | off  |
+-------------------------------+------+

Notes

sys.optimizer_switch_on() is a shortcut for sys.optimizer_switch_choice("on"); sys.optimizer_switch_off() is a shortcut for sys.optimizer_switch_choice("off");

See Also

• optimizer-switch Documentation for optimizer_switch