fixed column number fetchinmg for subqueries. (BUG#8020)

fixed cols() method call (it have to be called only after fix_fields())


mysql-test/r/subselect.result:
  Comparison subquery with * and row
mysql-test/t/subselect.test:
  Comparison subquery with * and row
sql/item_cmpfunc.h:
  initialization allowed_arg_cols for autodetection
sql/item_func.cc:
  support of allowed_arg_cols autodetection by first argument
sql/item_func.h:
  commant
sql/item_subselect.cc:
  correct column number fetching for subqueries
sql/sql_lex.h:
  method to check that UNION is prepared

1 files changed, 4 insertions, 2 deletions

diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 8516ea76a7e..2597427253c 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -1421,13 +1421,15 @@ int subselect_indexsubquery_engine::exec()
 
 uint subselect_single_select_engine::cols()
 {
-  return select_lex->item_list.elements;
+  DBUG_ASSERT(select_lex->join); // should be called after fix_fields()
+  return select_lex->join->fields_list.elements;
 }
 
 
 uint subselect_union_engine::cols()
 {
-  return unit->first_select()->item_list.elements;
+  DBUG_ASSERT(unit->is_prepared());  // should be called after fix_fields()
+  return unit->types.elements;
 }