BUG#3987 - if(int, aggregate(int))

mysql-test/r/func_if.result

@@ -58,3 +58,9 @@ select min(if(y -x > 5,y,NULL)), max(if(y - x > 5,y,NULL)) from t1;
 min(if(y -x > 5,y,NULL))	max(if(y - x > 5,y,NULL))
 6	56
 drop table t1;
+create table t1 (a int);
+insert t1 values (1),(2);
+select if(1>2,a,avg(a)) from t1;
+if(1>2,a,avg(a))
+1.5000
+drop table t1;

mysql-test/t/func_if.test

@@ -38,3 +38,12 @@ create table t1 (x int, y int);
 insert into t1 values (0,6),(10,16),(20,26),(30,10),(40,46),(50,56);
 select min(if(y -x > 5,y,NULL)), max(if(y - x > 5,y,NULL)) from t1;
 drop table t1;
+
+#
+# BUG#3987
+#
+create table t1 (a int);
+insert t1 values (1),(2);
+select if(1>2,a,avg(a)) from t1;
+drop table t1;
+

sql/item_cmpfunc.cc

@@ -535,8 +535,8 @@ Item_func_if::fix_length_and_dec()
   decimals=max(args[1]->decimals,args[2]->decimals);
   enum Item_result arg1_type=args[1]->result_type();
   enum Item_result arg2_type=args[2]->result_type();
-  bool null1=args[1]->null_value;
-  bool null2=args[2]->null_value;
+  bool null1=args[1]->const_item() && args[1]->null_value;
+  bool null2=args[2]->const_item() && args[2]->null_value;
 
   if (null1)
   {