Bug #20730220 : BACKPORT BUG#19880368 TO 5.1

Backport from mysql-5.5 to mysql-5.1 Bug#19880368 : GROUP_CONCAT CRASHES AFTER DUMP_LEAF_KEY Problem: find_order_by_list does not update the address of order_item correctly after resolving. Solution: Change the ref_by address for a order_by field if its SUM_FUNC_ITEM to the address of the field present in all_fields.

Author: Chaithra Gopalareddy

sql/sql_select.cc

@@ -14937,6 +14937,17 @@ find_order_in_list(THD *thd, Item **ref_pointer_array, TABLE_LIST *tables,
  uint el= all_fields.elements;
  all_fields.push_front(order_item); /* Add new field to field list. */
  ref_pointer_array[el]= order_item;
+ /*
+ If the order_item is a SUM_FUNC_ITEM, when fix_fields is called
+ ref_by is set to order->item which is the address of order_item.
+ But this needs to be address of order_item in the all_fields list.
+ As a result, when it gets replaced with Item_aggregate_ref
+ object in Item::split_sum_func2, we will be able to retrieve the
+ newly created object.
+ */
+ if (order_item->type() == Item::SUM_FUNC_ITEM)
+ ((Item_sum *)order_item)->ref_by= all_fields.head_ref();
+
  order->item= ref_pointer_array + el;
  return FALSE;
 }