MDEV-17606: Query returns wrong results (while using CHARACTER SET utf8)

The issue here was that the left expr and right expr of the ANY subquery
had different character sets, so we were converting the left expr to utf8 character set.
So when this conversion was happening we were actually converting the item inside the cache,
it looked like <cache>(convert(t1.l1 using utf8)), which is incorrect.
To fix this problem we are going to store the reference of the left expr and convert that
to utf8 character set, it would look like convert(<cache>(`test`.`t1`.`l1`) using utf8)

mysql-test/r/subselect4.result

@@ -2566,3 +2566,21 @@ SELECT sum(a), t2.a, t2.b FROM t2 HAVING t2.a IN (SELECT t2.b FROM t1);
 sum(a)	a	b
 6	1	1
 DROP TABLE t1,t2;
+#
+# MDEV-17606: Query returns wrong results (while using CHARACTER SET utf8)
+#
+CREATE TABLE t1(l1 varchar(10), i2 int);
+INSERT INTO t1 VALUES ('e',2),('o',6),('x',4);
+CREATE TABLE t2 (v1 varchar(10) CHARACTER SET utf8, KEY v1 (v1(3)));
+INSERT INTO t2 VALUES  ('k'),('rid'),('f'),('x');
+EXPLAIN EXTENDED SELECT * FROM t1 where  ( t1.l1 < ANY (SELECT MAX(t2.v1) FROM t2));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	4	100.00	
+Warnings:
+Note	1003	select `test`.`t1`.`l1` AS `l1`,`test`.`t1`.`i2` AS `i2` from `test`.`t1` where <nop>(<in_optimizer>(`test`.`t1`.`l1`,(<max>(select max(`test`.`t2`.`v1`) from `test`.`t2`) > convert(<cache>(`test`.`t1`.`l1`) using utf8))))
+SELECT * FROM t1 where  ( t1.l1 < ANY (SELECT MAX(t2.v1) FROM t2));
+l1	i2
+e	2
+o	6
+DROP TABLE t1, t2;

mysql-test/t/subselect4.test

@@ -2099,3 +2099,16 @@ SET @@sql_select_limit= @save_sql_select_limit;
 eval EXPLAIN EXTENDED $query;
 eval $query;
 DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-17606: Query returns wrong results (while using CHARACTER SET utf8)
+--echo #
+
+CREATE TABLE t1(l1 varchar(10), i2 int);
+INSERT INTO t1 VALUES ('e',2),('o',6),('x',4);
+CREATE TABLE t2 (v1 varchar(10) CHARACTER SET utf8, KEY v1 (v1(3)));
+INSERT INTO t2 VALUES  ('k'),('rid'),('f'),('x');
+
+EXPLAIN EXTENDED SELECT * FROM t1 where  ( t1.l1 < ANY (SELECT MAX(t2.v1) FROM t2));
+SELECT * FROM t1 where  ( t1.l1 < ANY (SELECT MAX(t2.v1) FROM t2));
+DROP TABLE t1, t2;

sql/item_subselect.cc

@@ -2015,7 +2015,7 @@ bool Item_allany_subselect::transform_into_max_min(JOIN *join)
     The swap is needed for expressions of type 'f1 < ALL ( SELECT ....)'
     where we want to evaluate the sub query even if f1 would be null.
   */
-  subs= func->create_swap(thd, *(optimizer->get_cache()), subs);
+  subs= func->create_swap(thd, expr, subs);
   thd->change_item_tree(place, subs);
   if (subs->fix_fields(thd, &subs))
     DBUG_RETURN(true);