3 files changed, 26 insertions, 3 deletions

diff --git a/sql/item.h b/sql/item.h
index f66892a76cc..4bee370642e 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -556,10 +556,17 @@ public:
   Field *make_string_field(TABLE *table);
   virtual bool fix_fields(THD *, Item **);
   /*
-    should be used in case where we are sure that we do not need
+    This method should be used in case where we are sure that we do not need
     complete fix_fields() procedure.
-  */
-  inline void quick_fix_field() { fixed= 1; }
+    Usually this method is used by the optimizer when it has to create a new
+    item out of other already fixed items. For example, if the optimizer has
+    to create a new Item_func for an inferred equality whose left and right
+    parts are already fixed items. In some cases the optimizer cannot use
+    directly fixed items as the arguments of the created functional item, 
+    but rather uses intermediate type conversion items. Then the method is
+    supposed to be applied recursively.  
+  */
+  virtual inline void quick_fix_field() { fixed= 1; }
   /* Function returns 1 on overflow and -1 on fatal errors */
   int save_in_field_no_warnings(Field *field, bool no_conversions);
   virtual int save_in_field(Field *field, bool no_conversions);
diff --git a/sql/item_func.cc b/sql/item_func.cc
index c35db7ad1cb..ab84303101c 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -202,6 +202,21 @@ Item_func::fix_fields(THD *thd, Item **ref)
   return FALSE;
 }
 
+void
+Item_func::quick_fix_field()
+{
+  Item **arg,**arg_end;
+  if (arg_count)
+  {
+    for (arg=args, arg_end=args+arg_count; arg != arg_end ; arg++)
+    {
+      if (!(*arg)->fixed)
+        (*arg)->quick_fix_field();
+    }
+  }
+  fixed= 1;
+}
+
 
 bool Item_func::walk(Item_processor processor, bool walk_subquery,
                      uchar *argument)
diff --git a/sql/item_func.h b/sql/item_func.h
index e45638472e4..3d2cb709ce3 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -117,6 +117,7 @@ public:
   // Constructor used for Item_cond_and/or (see Item comment)
   Item_func(THD *thd, Item_func *item);
   bool fix_fields(THD *, Item **ref);
+  void quick_fix_field();
   table_map used_tables() const;
   table_map not_null_tables() const;
   void update_used_tables();