revision of fix_fields() calls (BUG2838)

mysql-test/r/subselect.result:
  test suite for BUG#2838
mysql-test/t/subselect.test:
  test suite for BUG#2838
sql/item.cc:
  revision of fix_fields() calls
  removed unnecessary variabl, and used correct last parameter of fix_fields()
sql/item_cmpfunc.cc:
  revision of fix_fields() calls (BUG#2838)
sql/item_func.cc:
  revision of fix_fields() calls
sql/item_row.cc:
  changed for efficience (and to be similar for Item_func::fix_fields)
sql/item_subselect.cc:
  fixed last arguments for fix_fields call
sql/item_sum.cc:
  layout fixed
  revision of fix_fields() calls
sql/log_event.cc:
  revision of fix_fields() calls
sql/set_var.cc:
  revision of fix_fields() calls
sql/sql_base.cc:
  revision of fix_fields() calls
sql/sql_class.cc:
  revision of fix_fields() calls
sql/sql_handler.cc:
  revision of fix_fields() calls

1 files changed, 7 insertions, 3 deletions

diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 10b50fa5b3b..762c2df6cf7 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -191,17 +191,21 @@ Item_sum_num::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 bool
 Item_sum_hybrid::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 {
-  Item *item=args[0];
+  Item *item= args[0];
   if (!thd->allow_sum_func)
   {
     my_error(ER_INVALID_GROUP_FUNC_USE,MYF(0));
     return 1;
   }
   thd->allow_sum_func=0;			// No included group funcs
+
+  // 'item' can be changed during fix_fields
   if (!item->fixed &&
-      item->fix_fields(thd, tables, args) || item->check_cols(1))
+      item->fix_fields(thd, tables, args) ||
+      (item= args[0])->check_cols(1))
     return 1;
-  hybrid_type=item->result_type();
+
+  hybrid_type= item->result_type();
   if (hybrid_type == INT_RESULT)
   {
     cmp_charset= &my_charset_bin;