Fixed bug #24420.

Objects of the classes Item_func_is_not_null_test and Item_func_trig_cond
must be transparent for the method Item::split_sum_func2 as these classes
are pure helpers. It means that the method Item::split_sum_func2 should
look at those objects as at pure wrappers.

mysql-test/r/subselect3.result

@@ -629,3 +629,19 @@ cc	NULL	NULL
 aa	1	1
 bb	NULL	NULL
 drop table t1,t2;
+create table t1 (a int, b int);
+insert into t1 values (0,0), (2,2), (3,3);
+create table t2 (a int, b int);
+insert into t2 values (1,1), (3,3);
+select a, b, (a,b) in (select a, min(b) from t2 group by a) Z from t1;
+a	b	Z
+0	0	0
+2	2	0
+3	3	1
+insert into t2 values (NULL,4);
+select a, b, (a,b) in (select a, min(b) from t2 group by a) Z from t1;
+a	b	Z
+0	0	0
+2	2	0
+3	3	1
+drop table t1,t2;

mysql-test/t/subselect3.test

@@ -472,3 +472,20 @@ select oref, a, a in (select min(ie) from t1 where oref=t2.oref group by grp) Z
 
 drop table t1,t2;
 
+#
+# BUG#24420: row-based IN suqueries with aggregation when the left operand
+#            of the subquery predicate may contain NULL values
+#
+
+create table t1 (a int, b int);
+insert into t1 values (0,0), (2,2), (3,3);
+create table t2 (a int, b int);
+insert into t2 values (1,1), (3,3);
+
+select a, b, (a,b) in (select a, min(b) from t2 group by a) Z from t1;
+
+insert into t2 values (NULL,4);
+select a, b, (a,b) in (select a, min(b) from t2 group by a) Z from t1;
+
+drop table t1,t2;
+

sql/item.cc

@@ -1242,7 +1242,10 @@ void Item::split_sum_func2(THD *thd, Item **ref_pointer_array,
   if (type() == SUM_FUNC_ITEM && skip_registered && 
       ((Item_sum *) this)->ref_by)
     return;                                                 
-  if (type() != SUM_FUNC_ITEM && with_sum_func)
+  if ((type() != SUM_FUNC_ITEM && with_sum_func) ||
+      (type() == FUNC_ITEM &&
+       (((Item_func *) this)->functype() == Item_func::ISNOTNULLTEST_FUNC ||
+        ((Item_func *) this)->functype() == Item_func::TRIG_COND_FUNC)))
   {
     /* Will split complicated items and ignore simple ones */
     split_sum_func(thd, ref_pointer_array, fields);