fixed fix_fields() parameters for GROUP_CONCAT() ORDER BY clause

(BUG#1537)


mysql-test/r/func_gconcat.result:
  test of BUG#1537
mysql-test/t/func_gconcat.test:
  test of BUG#1537
sql/item_sum.cc:
  passing correct address of pointer to item to fix_dields(), using that addres to get access to item after fix_fields

mysql-test/r/func_gconcat.result

@@ -196,3 +196,14 @@ insert into t1 values('test'),('test2');
 select * from t1 having group_concat(bar)='';
 bar
 drop table t1;
+create table t1 (a int, a1 varchar(10));
+create table t2 (a0 int);
+insert into t1 values (0,"a"),(0,"b"),(1,"c");
+insert into t2 values (1),(2),(3);
+select  group_concat(a1 order by (t1.a IN (select a0 from t2))) from t1;
+group_concat(a1 order by (t1.a IN (select a0 from t2)))
+b,a,c
+select  group_concat(a1 order by (t1.a)) from t1;
+group_concat(a1 order by (t1.a))
+b,a,c
+drop table t1, t2;

mysql-test/t/func_gconcat.test

@@ -119,4 +119,11 @@ insert into t1 values('test'),('test2');
 select * from t1 having group_concat(bar)='';
 drop table t1;
 
-
+# ORDER BY fix_fields()
+create table t1 (a int, a1 varchar(10));
+create table t2 (a0 int);
+insert into t1 values (0,"a"),(0,"b"),(1,"c");
+insert into t2 values (1),(2),(3);
+select  group_concat(a1 order by (t1.a IN (select a0 from t2))) from t1;
+select  group_concat(a1 order by (t1.a)) from t1;
+drop table t1, t2;
\ No newline at end of file

sql/item_sum.cc

@@ -1773,8 +1773,8 @@ Item_func_group_concat::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   for (i= 0 ; i < arg_count_order ; i++)
   {
     ORDER *order_item= order[i];
-    Item *item=*order_item->item;
-    if (item->fix_fields(thd, tables, &item) || item->check_cols(1))
+    if ((*order_item->item)->fix_fields(thd, tables, order_item->item) ||
+	(*order_item->item)->check_cols(1))
       return 1;
   }
   result_field= 0;