Merge from mysql-5.1 to mysql-5.5

sql/set_var.h

@@ -225,13 +225,23 @@ class set_var :public set_var_base
     if (value_arg && value_arg->type() == Item::FIELD_ITEM)
     {
       Item_field *item= (Item_field*) value_arg;
-      if (!(value=new Item_string(item->field_name,
-                                  (uint) strlen(item->field_name),
-                                  system_charset_info))) // names are utf8
-        value=value_arg;                        /* Give error message later */
+      if (item->field_name)
+      {
+        if (!(value= new Item_string(item->field_name,
+                                     (uint) strlen(item->field_name),
+                                     system_charset_info))) // names are utf8
+	  value= value_arg;			/* Give error message later */
+      }
+      else
+      {
+        /* Both Item_field and Item_insert_value will return the type as
+        Item::FIELD_ITEM. If the item->field_name is NULL, we assume the
+        object to be Item_insert_value. */
+        value= value_arg;
+      }
     }
     else
-      value=value_arg;
+      value= value_arg;
   }
   int check(THD *thd);
   int update(THD *thd);