i1	i2	c2
1	8	c
1	6	c

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=off,table_elimination=on,extended_keys=off,exists_to_in=off,expensive_pred_static_pushdown=off

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	100.00	
1	PRIMARY	t2	index	NULL	c2	7	NULL	2	100.00	Using where; Subqueries: 3; Using index; Using join buffer (flat, BNL join)
2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Subqueries: 3
2	MATERIALIZED	t2	ref	c2	c2	2	test.t3.c3	1	100.00	Using index
3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
4	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
NULL	UNION RESULT	<union3,4>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
Warnings:
Note	1003	select `test`.`t1`.`i1` AS `i1`,`test`.`t2`.`i2` AS `i2`,`test`.`t2`.`c2` AS `c2` from `test`.`t1` semi join (`test`.`t3` join `test`.`t2`) join `test`.`t2` where ((`test`.`t2`.`c2` = `test`.`t3`.`c3`) and <not>(<in_optimizer>(`test`.`t3`.`i3`,(<min>(select 4 union select 8) <= <cache>(`test`.`t3`.`i3`)))))