id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	index_merge	index_block_id,index_placeholder_var,index_nav_item_page_id,index_prev_id,index_nipi_pv_pi_ih_si	index_nav_item_page_id,index_placeholder_var,index_prev_id	5,242,5	NULL	1	7.41	Using intersect(index_nav_item_page_id,index_placeholder_var,index_prev_id); Using where; Using filesort
1	SIMPLE	t2	NULL	eq_ref	PRIMARY	PRIMARY	4	jolliotpmntest.t1.block_id	1	100.00	NULL