@@optimizer_switch
index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,subquery_materialization_cost_based=on,use_index_extensions=on
col1	col2	col3
1	2	2013-03-08 16:47:39
1	2	2013-03-08 16:50:27
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	table1	index_merge	PRIMARY,col1,col2	col1,col2	8,8	NULL	2	Using intersect(col1,col2); Using where; Using index; Using filesort
@@optimizer_switch
index_merge=off,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,subquery_materialization_cost_based=on,use_index_extensions=on
col1	col2	col3
1	2	2013-03-08 16:47:39
1	2	2013-03-08 16:50:27
1	2	2013-03-11 16:33:04
1	2	2013-03-11 16:33:24
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	table1	ref	PRIMARY,col1,col2	col1	8	const	4	Using where; Using filesort