fixed printing of sum(distinct ) & avg(distinct ) & cast(... as decimal) (BUG#7015, BUG#11387)

mysql-test/r/view.result:
  using sum(distinct ), cast(... as decimal) & avg(distinct ) in views
mysql-test/t/view.test:
  using sum(distinct ), cast(... as decimal) & avg(distinct ) in views
sql/item.h:
  Add a comment for Item::print
sql/item_func.cc:
  Use functype(), not func_name() for item equvalence detection
sql/item_func.h:
  Missed function typoes added
  Add a comment for Item_func::func_name()
  style fix
sql/item_strfunc.cc:
  Use functype(), not func_name() for item equvalence detection
sql/item_strfunc.h:
  Add missing func_name and func_type
sql/item_sum.cc:
  Item_sum func_name report beggining of function till first argument
sql/item_sum.h:
  Item_sum func_name report beggining of function till first argument
sql/item_timefunc.cc:
  Use functype(), not func_name() for item equvalence detection
sql/item_timefunc.h:
  Add missing func_name and func_type
sql/item_uniq.h:
  Add missing func_name

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/item.h b/sql/item.h
index 820624afd2b..7ab03bae506 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -468,6 +468,18 @@ public:
   */
   virtual bool const_during_execution() const 
   { return (used_tables() & ~PARAM_TABLE_BIT) == 0; }
+  /*
+    This is an essential method for correct functioning of VIEWS.
+    To save a view in an .frm file we need its unequivocal
+    definition in SQL that takes into account sql_mode and
+    environmental settings.  Currently such definition is restored
+    by traversing through the parsed tree of a view and
+    print()'ing SQL syntax of every node to a String buffer. This
+    method is used to print the SQL definition of an item. The
+    second use of this method is for EXPLAIN EXTENDED, to print
+    the SQL of a query after all optimizations of the parsed tree
+    have been done.
+  */
   virtual void print(String *str_arg) { str_arg->append(full_name()); }
   void print_item_w_name(String *);
   virtual void update_used_tables() {}