MariaDB 5.3 optimizer_switch
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@@optimizer_switch is a server variable that one can use to enable/disable specific optimizations. For generic syntax, see Switchable Optimizations in MySQL Manual.
Below is a list of all @@optimizer_switch flags available in MariaDB 5.3:
| Flag and default setting | Controlled feature | Introduced in |
|---|---|---|
derived_merge=off | MariaDB 5.3 | |
derived_with_keys=off | MariaDB 5.3 | |
index_condition_pushdown=off | Index Condition Pushdown | MariaDB 5.3 |
index_merge=on | All index_merge optimizations | MySQL 5.1.x |
index_merge_union=on | index_merge union | MySQL 5.1.x |
index_merge_sort_union=on | index_merge sort-intersection | MySQL 5.1.x |
index_merge_intersection=on | index_merge intersection | MySQL 5.1.x |
index_merge_sort_intersection=off | MariaDB 5.3 | |
mrr=off | ||
mrr_cost_based=off | ||
mrr_sort_keys=off | ||
materialization=off | ||
subquery_cache=off | ||
semijoin=off | ||
firstmatch=off | ||
loosescan=off | ||
in_to_exists=on | ||
partial_match_rowid_merge=on | ||
partial_match_table_scan=on | ||
join_cache_bka=on | ||
join_cache_hashed=on | ||
join_cache_incremental=on | ||
outer_join_with_cache=off | ||
semijoin_with_cache=off | ||
optimize_join_buffer_size=off | ||
table_elimination=on |
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