Fixed bugs mdev-5927 and mdev-6116.

Both bugs are caused by the same problem: the function optimize_cond() should
update the value of *cond_equal rather than the value of join->cond_equal,
because it is called not only for the WHERE condition, but for the HAVING
condition as well.

mysql-test/r/having.result

@@ -635,3 +635,32 @@ Note	1003	select min(`test`.`t1`.`f10`) AS `field1` from `test`.`t1` join `test`
 set optimizer_switch=@save_optimizer_switch;
 drop table t1,t2,t3;
 End of 5.2 tests
+#
+# Bug mdev-6116: an equality in the conjunction of HAVING
+#                and IN subquery in WHERE
+# (The bug is caused by the same problem as bug mdev-5927)
+#
+CREATE TABLE t1 (f_key varchar(1), f_nokey varchar(1), INDEX(f_key));
+INSERT INTO t1 VALUES ('v','v'),('s','s');
+CREATE TABLE t2 (f_int int, f_key varchar(1), INDEX(f_key));
+INSERT INTO t2 VALUES 
+(4,'j'),(6,'v'),(3,'c'),(5,'m'),(3,'d'),(2,'d'),(2,'y'),
+(9,'t'),(3,'d'),(8,'s'),(1,'r'),(8,'m'),(8,'b'),(5,'x');
+SELECT t2.f_int FROM t1 INNER JOIN t2 ON (t2.f_key = t1.f_nokey) 
+WHERE t1.f_nokey IN ( 
+SELECT t1.f_key FROM t1, t2 WHERE t1.f_key = t2.f_key 
+) HAVING t2.f_int >= 0 AND t2.f_int != 0;
+f_int
+6
+8
+DROP TABLE t1,t2;
+#
+# Bug mdev-5927: an equality in the conjunction of HAVING
+#                and an equality in WHERE
+#
+CREATE TABLE t1 (pk int PRIMARY KEY, f int NOT NULL, INDEX(f));
+INSERT INTO t1 VALUES (1,0), (2,8);
+SELECT * FROM t1 WHERE f = 2 HAVING ( pk IN ( SELECT 9 ) AND f != 0 );
+pk	f
+DROP TABLE t1;
+End of 5.3 tests

mysql-test/t/having.test

@@ -657,3 +657,39 @@ set optimizer_switch=@save_optimizer_switch;
 drop table t1,t2,t3;
 
 --echo End of 5.2 tests
+
+--echo #
+--echo # Bug mdev-6116: an equality in the conjunction of HAVING
+--echo #                and IN subquery in WHERE
+--echo # (The bug is caused by the same problem as bug mdev-5927)
+--echo #
+
+CREATE TABLE t1 (f_key varchar(1), f_nokey varchar(1), INDEX(f_key));
+INSERT INTO t1 VALUES ('v','v'),('s','s');
+
+CREATE TABLE t2 (f_int int, f_key varchar(1), INDEX(f_key));
+INSERT INTO t2 VALUES 
+(4,'j'),(6,'v'),(3,'c'),(5,'m'),(3,'d'),(2,'d'),(2,'y'),
+(9,'t'),(3,'d'),(8,'s'),(1,'r'),(8,'m'),(8,'b'),(5,'x');
+
+SELECT t2.f_int FROM t1 INNER JOIN t2 ON (t2.f_key = t1.f_nokey) 
+WHERE t1.f_nokey IN ( 
+  SELECT t1.f_key FROM t1, t2 WHERE t1.f_key = t2.f_key 
+) HAVING t2.f_int >= 0 AND t2.f_int != 0;
+
+DROP TABLE t1,t2;
+
+--echo #
+--echo # Bug mdev-5927: an equality in the conjunction of HAVING
+--echo #                and an equality in WHERE
+--echo #
+
+CREATE TABLE t1 (pk int PRIMARY KEY, f int NOT NULL, INDEX(f));
+INSERT INTO t1 VALUES (1,0), (2,8);
+
+SELECT * FROM t1 WHERE f = 2 HAVING ( pk IN ( SELECT 9 ) AND f != 0 );
+
+DROP TABLE t1;
+
+--echo End of 5.3 tests
+

sql/sql_select.cc

@@ -13234,7 +13234,7 @@ optimize_cond(JOIN *join, COND *conds,
     conds= remove_eq_conds(thd, conds, cond_value);
     if (conds && conds->type() == Item::COND_ITEM &&
         ((Item_cond*) conds)->functype() == Item_func::COND_AND_FUNC)
-      join->cond_equal= &((Item_cond_and*) conds)->cond_equal;
+      *cond_equal= &((Item_cond_and*) conds)->cond_equal;
     DBUG_EXECUTE("info",print_where(conds,"after remove", QT_ORDINARY););
   }
   DBUG_RETURN(conds);