1 files changed, 35 insertions, 1 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index f1a2b11aaa8..e7bef18e629 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -239,6 +239,40 @@ public:
   Item *neg_transformer(THD *thd);
 };
 
+
+/*
+  The class Item_func_trig_cond is used for guarded predicates 
+  which are employed only for internal purposes.
+  A guarded predicates is an object consisting of an a regular or
+  a guarded predicate P and a pointer to a boolean guard variable g. 
+  A guarded predicate P/g is evaluated to true if the value of the
+  guard g is false, otherwise it is evaluated to the same value that
+  the predicate P: val(P/g)= g ? val(P):true.
+  Guarded predicates allow us to include predicates into a conjunction
+  conditionally. Currently they are utilized for pushed down predicates
+  in queries with outer join operations.
+
+  In the future, probably, it makes sense to extend this class to
+  the objects consisting of three elements: a predicate P, a pointer
+  to a variable g and a firing value s with following evaluation
+  rule: val(P/g,s)= g==s? val(P) : true. It will allow us to build only
+  one item for the objects of the form P/g1/g2... 
+
+  Objects of this class are built only for query execution after
+  the execution plan has been already selected. That's why this
+  class needs only val_int out of generic methods. 
+*/
+
+class Item_func_trig_cond: public Item_bool_func
+{
+  bool *trig_var;
+public:
+  Item_func_trig_cond(Item *a, bool *f) : Item_bool_func(a) { trig_var= f; }
+  longlong val_int() { return *trig_var ? args[0]->val_int() : 1; }
+  enum Functype functype() const { return TRIG_COND_FUNC; };
+  const char *func_name() const { return "trigcond"; };
+};
+
 class Item_func_not_all :public Item_func_not
 {
   bool abort_on_null;
@@ -824,7 +858,7 @@ public:
   }
   const char *func_name() const { return "isnotnull"; }
   optimize_type select_optimize() const { return OPTIMIZE_NULL; }
-  table_map not_null_tables() const { return 0; }
+  table_map not_null_tables() const { return used_tables(); }
   Item *neg_transformer(THD *thd);
   void print(String *str);
   CHARSET_INFO *compare_collation() { return args[0]->collation.collation; }