bad merge fixed for b4981.

f1	f2

1	1

drop table t1,t2;

CREATE TABLE t1(a int, b int, c int, KEY b(b), KEY c(c));

insert into t1 values (1,0,0),(2,0,0);

CREATE TABLE t2 (a int, b varchar(2), c varchar(2), PRIMARY KEY(a));

insert into t2 values (1,'',''), (2,'','');

CREATE TABLE t3 (a int, b int, PRIMARY KEY (a,b), KEY a (a), KEY b (b));

insert into t3 values (1,1),(1,2);

explain select straight_join DISTINCT t2.a,t2.b, t1.c from t1, t3, t2 

where (t1.c=t2.a or (t1.c=t3.a and t2.a=t3.b)) and t1.b=556476786 and 

t2.b like '%%' order by t2.b limit 0,1;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ref	b,c	b	5	const	1	Using where; Using temporary; Using filesort

1	SIMPLE	t3	index	PRIMARY,a,b	PRIMARY	8	NULL	2	Using index

1	SIMPLE	t2	ALL	PRIMARY	NULL	NULL	NULL	2	Range checked for each record (index map: 0x1)

DROP TABLE t1,t2,t3;

CREATE TABLE t1 ( city char(30) );

INSERT INTO t1 VALUES ('London');

INSERT INTO t1 VALUES ('Paris');

1	SIMPLE	t1	range	PRIMARY,b	b	5	NULL	3	Using where

1	SIMPLE	t2	ref	c	c	5	test.t1.a	2	Using where

DROP TABLE t1, t2;

CREATE TABLE t1(a int, b int, c int, KEY b(b), KEY c(c));

insert into t1 values (1,0,0),(2,0,0);

CREATE TABLE t2 (a int, b varchar(2), c varchar(2), PRIMARY KEY(a));

insert into t2 values (1,'',''), (2,'','');

CREATE TABLE t3 (a int, b int, PRIMARY KEY (a,b), KEY a (a), KEY b (b));

insert into t3 values (1,1),(1,2);

explain select straight_join DISTINCT t2.a,t2.b, t1.c from t1, t3, t2 

where (t1.c=t2.a or (t1.c=t3.a and t2.a=t3.b)) and t1.b=556476786 and 

t2.b like '%%' order by t2.b limit 0,1;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ref	b,c	b	5	const	1	Using where; Using temporary; Using filesort

1	SIMPLE	t3	index	PRIMARY,a,b	PRIMARY	8	NULL	2	Using index

1	SIMPLE	t2	ALL	PRIMARY	NULL	NULL	NULL	2	Range checked for each record (index map: 0x1)

DROP TABLE t1,t2,t3;