id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	b	NULL	ALL	PRIMARY,idx-auth_item-type	NULL	NULL	NULL	162	95.68	Using where
1	SIMPLE	a	NULL	eq_ref	PRIMARY	PRIMARY	388	portal.b.name,const	1	100.00	Using index