Fixed LP bug #884175.

If in the where clause of the a query some comparison conditions on the
field under a MIN/MAX aggregate function contained constants whose sizes
exceeded the size of the field then the query could return a wrong result
when the optimizer had chosen to apply the MIN/MAX optimization.
With such conditions the MIN/MAX optimization still could be applied, yet
it would require a more thorough analysis of the keys built to find
the value of MIN/MAX aggregate functions with index look-ups.   
The current patch just prohibits using the MIN/MAX optimization in this
situation.

2 files changed, 80 insertions, 0 deletions

diff --git a/mysql-test/r/func_group.result b/mysql-test/r/func_group.result
index 3608f587572..c07d16cb3f4 100644
--- a/mysql-test/r/func_group.result
+++ b/mysql-test/r/func_group.result
@@ -1828,4 +1828,51 @@ NULL
 NULL
 DROP TABLE t1,t2,t3;
 #
+# Bug #884175: MIN/MAX for short varchar = long const  
+#
+CREATE TABLE t1 (f1 varchar(1), f2 varchar(1), KEY (f2));
+INSERT INTO t1 VALUES ('b', 'b'), ('a','a');
+EXPLAIN 
+SELECT MAX(f1) FROM t1 WHERE f1 = 'abc';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT MAX(f1) FROM t1 WHERE f1 = 'abc';
+MAX(f1)
+NULL
+EXPLAIN
+SELECT MAX(f2) FROM t1 WHERE f2 = 'abc';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	f2	f2	4	const	1	Using where; Using index
+SELECT MAX(f2) FROM t1 WHERE f2 = 'abc';
+MAX(f2)
+NULL
+EXPLAIN
+SELECT MIN(f1) FROM t1 WHERE f1 >= 'abc';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT MIN(f1) FROM t1 WHERE f1 >= 'abc';
+MIN(f1)
+b
+EXPLAIN
+SELECT MIN(f2) FROM t1 WHERE f2 >= 'abc';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	f2	f2	4	NULL	2	Using where; Using index
+SELECT MIN(f2) FROM t1 WHERE f2 >= 'abc';
+MIN(f2)
+b
+EXPLAIN
+SELECT MIN(f1) FROM t1 WHERE f1 BETWEEN 'abc' AND 'b' ;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT MIN(f1) FROM t1 WHERE f1 BETWEEN 'abc' AND 'b' ;
+MIN(f1)
+b
+EXPLAIN
+SELECT MIN(f2) FROM t1 WHERE f2 BETWEEN 'abc' AND 'b' ;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	f2	f2	4	NULL	2	Using where; Using index
+SELECT MIN(f2) FROM t1 WHERE f2 BETWEEN 'abc' AND 'b' ;
+MIN(f2)
+b
+DROP TABLE t1;
 End of 5.2 tests
diff --git a/mysql-test/t/func_group.test b/mysql-test/t/func_group.test
index 3939d53cb31..927c4b084da 100644
--- a/mysql-test/t/func_group.test
+++ b/mysql-test/t/func_group.test
@@ -1194,4 +1194,37 @@ SELECT (SELECT MIN(t1.a) FROM t1,t2 WHERE t2.a = t3.b) FROM t3;
 DROP TABLE t1,t2,t3;
 
 --echo #
+--echo # Bug #884175: MIN/MAX for short varchar = long const  
+--echo #
+
+CREATE TABLE t1 (f1 varchar(1), f2 varchar(1), KEY (f2));
+INSERT INTO t1 VALUES ('b', 'b'), ('a','a');
+
+EXPLAIN 
+SELECT MAX(f1) FROM t1 WHERE f1 = 'abc';
+SELECT MAX(f1) FROM t1 WHERE f1 = 'abc';
+
+EXPLAIN
+SELECT MAX(f2) FROM t1 WHERE f2 = 'abc';
+SELECT MAX(f2) FROM t1 WHERE f2 = 'abc';
+
+EXPLAIN
+SELECT MIN(f1) FROM t1 WHERE f1 >= 'abc';
+SELECT MIN(f1) FROM t1 WHERE f1 >= 'abc';
+
+EXPLAIN
+SELECT MIN(f2) FROM t1 WHERE f2 >= 'abc';
+SELECT MIN(f2) FROM t1 WHERE f2 >= 'abc';
+
+EXPLAIN
+SELECT MIN(f1) FROM t1 WHERE f1 BETWEEN 'abc' AND 'b' ;
+SELECT MIN(f1) FROM t1 WHERE f1 BETWEEN 'abc' AND 'b' ;
+
+EXPLAIN
+SELECT MIN(f2) FROM t1 WHERE f2 BETWEEN 'abc' AND 'b' ;
+SELECT MIN(f2) FROM t1 WHERE f2 BETWEEN 'abc' AND 'b' ;
+
+DROP TABLE t1;
+
+
 --echo End of 5.2 tests