sql_select.cc, sql_class.h:

  Reversed the changes to fix bug #12095 after review
  done by SergeyG. Applied a fix suggested by him.

sql/sql_class.h

@@ -1325,12 +1325,10 @@ public:
   bool  using_indirect_summary_function;
   /* If >0 convert all blob fields to varchar(convert_blob_length) */
   uint  convert_blob_length; 
-  bool need_const; /* <=> const items are saved in tmp table */
 
   TMP_TABLE_PARAM()
     :copy_field(0), group_parts(0),
-    group_length(0), group_null_parts(0), convert_blob_length(0),
-    need_const(0) 
+    group_length(0), group_null_parts(0), convert_blob_length(0)
   {}
   ~TMP_TABLE_PARAM()
   {

sql/sql_select.cc

@@ -5201,8 +5201,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
 	param->using_indirect_summary_function=1;
 	continue;
       }
-      if (item->const_item() && (int) hidden_field_count <= 0 &&
-          !param->need_const)
+      if (item->const_item() && (int) hidden_field_count <= 0)
         continue; // We don't have to store this
     }
     if (type == Item::SUM_FUNC_ITEM && !group && !save_sum_fields)