Fix for Bug #9913 "udf_deinit is not called after execution of PS"

(aka "deinit is not called when calling udf from trigger").

We should call udf_deinit() function during cleanup phase after prepared
(or ordinary) statement execution instead of calling it from Item's
desctructor.

No test case is provided since it is hard to test UDF's from our test
suite.


sql/item_func.cc:
  udf_handler:
   Moved all functionality from udf_handler::~udf_handler() to 
   udf_handler::cleanup() method which will be called after
   each PS execution, thus allowing udf_deinit() to be executed
   symetrically with udf_init() (which is executed for each
   execution of PS).
  Added Item_udf_func::cleanup() which performs proper cleanup after
  execution of PS with UDF function.
sql/item_func.h:
  Added Item_udf_func::cleanup() method to perform cleanup properly after
  execution of PS with UDF function.
sql/item_sum.cc:
  Added Item_udf_sum::cleanup() method to perform cleanup properly after
  execution of PS with aggregate UDF function.
sql/item_sum.h:
  Added Item_udf_sum::cleanup() method to perform cleanup properly after
  execution of PS with aggregate UDF function.
sql/sql_udf.h:
  Added udf_handler::cleanup() method declaration which is responsible
  for cleaning up UDF execution context at the end of execution of
  statement (using ~udf_handler() for this purprose did not worked for PS).

sql/item_func.cc

@@ -1617,6 +1617,13 @@ longlong Item_func_bit_count::val_int()
 #ifdef HAVE_DLOPEN
 
 udf_handler::~udf_handler()
+{
+  /* Everything should be properly cleaned up by this moment. */
+  DBUG_ASSERT(not_original || !(initialized || buffers));
+}
+
+
+void udf_handler::cleanup()
 {
   if (!not_original)
   {
@@ -1629,9 +1636,11 @@ udf_handler::~udf_handler()
         (*deinit)(&initid);
       }
       free_udf(u_d);
+      initialized= FALSE;
     }
     if (buffers)				// Because of bug in ecc
       delete [] buffers;
+    buffers= 0;
   }
 }
 
@@ -1871,6 +1880,12 @@ String *udf_handler::val_str(String *str,String *save_str)
 }
 
 
+void Item_udf_func::cleanup()
+{
+  udf.cleanup();
+  Item_func::cleanup();
+}
+
 
 double Item_func_udf_float::val()
 {

sql/item_func.h

@@ -786,6 +786,7 @@ public:
     fixed= 1;
     return res;
   }
+  void cleanup();
   Item_result result_type () const { return udf.result_type(); }
   table_map not_null_tables() const { return 0; }
 };

sql/item_sum.cc

@@ -1449,6 +1449,17 @@ bool Item_udf_sum::add()
   DBUG_RETURN(0);
 }
 
+void Item_udf_sum::cleanup()
+{
+  /*
+    udf_handler::cleanup() nicely handles case when we have not
+    original item but one created by copy_or_same() method.
+  */
+  udf.cleanup();
+  Item_sum::cleanup();
+}
+
+
 Item *Item_sum_udf_float::copy_or_same(THD* thd)
 {
   return new (thd->mem_root) Item_sum_udf_float(thd, this);

sql/item_sum.h

@@ -550,6 +550,7 @@ public:
   bool add();
   void reset_field() {};
   void update_field() {};
+  void cleanup();
 };
 
 

sql/sql_udf.h

@@ -67,6 +67,7 @@ class udf_handler :public Sql_alloc
   bool get_arguments();
   bool fix_fields(THD *thd,struct st_table_list *tlist,Item_result_field *item,
 		  uint arg_count,Item **args);
+  void cleanup();
   double val(my_bool *null_value)
   {
     if (get_arguments())