Fix of LP BUG#780386.

  
  ALL subquery should return TRUE if subquery rowa set is empty independently
  of left part.  The problem was that Item_func_(eq,ne,gt,ge,lt,le) do not
  call execution of second argument if first is NULL no in this case subquery
  will not be executed and when Item_func_not_all calls any_value() of the
  subquery or aggregation function which report that there was rows. So for
  NULL < ALL (SELECT...) result was FALSE instead of TRUE.
  
  Fix is just swapping of arguments of Item_func_(eq,ne,gt,ge,lt,le) (with
  changing the operation if it is needed) so that result will be the same
  (for examole a < b is equal to b > a). This fix exploit the fact that
  first argument will be executed in any case.

1 files changed, 5 insertions, 2 deletions

diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 415d81a5b58..6f0a38c1625 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -1076,8 +1076,11 @@ Item_in_subselect::single_value_transformer(JOIN *join,
       if (upper_item)
         upper_item->set_sub_test(item);
     }
-    /* fix fields is already called for  left expression */
-    substitution= func->create(left_expr, subs);
+    /*
+      The swap is needed for expressions of type 'f1 < ALL ( SELECT ....)'
+      where we want to evaluate the sub query even if f1 would be null.
+    */
+    substitution= func->create_swap(left_expr, subs);
     DBUG_RETURN(RES_OK);
   }