The optimizer thinks subquery is correlated while it is not

#

# LP BUG#680038 bool close_thread_table(THD*, TABLE**):

#               Assertion `table->key_read == 0' failed in EXPLAIN

#

CREATE TABLE t1 (f1 int,f3 int,f4 int) ;

INSERT IGNORE INTO t1 VALUES (NULL,1,0);

CREATE TABLE t2 (f2 int,f4 int,f5 int) ;

INSERT IGNORE INTO t2 VALUES (8,0,0),(5,0,0);

CREATE TABLE t3 (f4 int,KEY (f4)) ;

INSERT IGNORE INTO t3 VALUES (0),(0);

set @@optimizer_switch='semijoin=off';

EXPLAIN

SELECT * FROM t1 WHERE

(SELECT f2 FROM t2

WHERE f4 <= ALL

(SELECT max(SQ1_t1.f4)

FROM t3 AS SQ1_t1 JOIN t3 AS SQ1_t3 ON SQ1_t3.f4

GROUP BY SQ1_t1.f4));

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	

2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where

3	SUBQUERY	SQ1_t1	index	NULL	f4	5	NULL	2	Using index; Using temporary

3	SUBQUERY	SQ1_t3	index	f4	f4	5	NULL	2	Using where; Using index; Using join buffer (flat, BNL join)