[Maria-developers] bzr commit into MariaDB 5.1, with Maria 1.5:maria branch (igor:2779)

29 Jun 2010

#At lp:maria based on revid:knielsen@knielsen-hq.org-20091130132430-edrwle5zh6udx9rp

 2779 Igor Babaev	2010-06-28
      Optimization that checks for expressions whether they are always null.
      modified:
        mysql-test/r/func_in.result
        sql/item.h
        sql/item_cmpfunc.cc
        sql/item_cmpfunc.h
        sql/item_func.cc
        sql/item_func.h
        sql/item_sum.h
        sql/sql_select.cc
        sql/sql_udf.h

=== modified file 'mysql-test/r/func_in.result'

--- a/mysql-test/r/func_in.result	2009-10-05 05:27:36 +0000
+++ b/mysql-test/r/func_in.result	2010-06-29 00:24:26 +0000
@@ -642,10 +642,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_int	c_int	4	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (1, 2, 3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	c_decimal	c_decimal	3	NULL	3	Using where
@@ -654,10 +654,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_decimal	c_decimal	3	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_float IN (1, 2, 3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	c_float	c_float	4	NULL	3	Using where
@@ -666,10 +666,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_float	c_float	4	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_bit IN (1, 2, 3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	c_bit	c_bit	2	NULL	3	Using where
@@ -678,10 +678,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_bit	c_bit	2	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_date 
 IN ('2009-09-01', '2009-09-02', '2009-09-03');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -692,10 +692,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_date	c_date	3	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_date IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_date IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_datetime
 IN ('2009-09-01 00:00:01', '2009-09-02 00:00:01', '2009-09-03 00:00:01');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -706,10 +706,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_datetime	c_datetime	8	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_datetime IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_datetime IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_timestamp
 IN ('2009-09-01 00:00:01', '2009-09-01 00:00:02', '2009-09-01 00:00:03');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -720,10 +720,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_timestamp	c_timestamp	4	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_timestamp IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_timestamp IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_year IN (1, 2, 3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	c_year	c_year	1	NULL	3	Using where
@@ -732,10 +732,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_year	c_year	1	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_char IN ('1', '2', '3');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	c_char	c_char	10	NULL	3	Using where
@@ -744,10 +744,10 @@ id	select_type	table	type	possible_keys	
 1	SIMPLE	t1	range	c_char	c_char	10	NULL	3	Using where
 EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL, NULL);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 DROP TABLE t1;
 #
 End of 5.1 tests

=== modified file 'sql/item.h'
--- a/sql/item.h	2009-11-16 20:49:51 +0000
+++ b/sql/item.h	2010-06-29 00:24:26 +0000
@@ -774,6 +774,7 @@ public:
     will not change until next fix_fields) and its value is known.
   */
   virtual bool const_item() const { return used_tables() == 0; }
+  virtual bool is_always_null() const { return 0; }
   /* 
     Returns true if this is constant but its value may be not known yet.
     (Can be used for parameters of prep. stmts or of stored procedures.)
@@ -1563,6 +1564,7 @@ public:
   enum Item_result result_type () const { return STRING_RESULT; }
   enum_field_types field_type() const   { return MYSQL_TYPE_NULL; }
   bool basic_const_item() const { return 1; }
+  bool is_always_null() const { return 1; }
   Item *clone_item() { return new Item_null(name); }
   bool is_null() { return 1; }
 

=== modified file 'sql/item_cmpfunc.cc'
--- a/sql/item_cmpfunc.cc	2009-11-16 20:49:51 +0000
+++ b/sql/item_cmpfunc.cc	2010-06-29 00:24:26 +0000
@@ -1983,6 +1983,19 @@ bool Item_func_between::fix_fields(THD *
                           (args[1]->not_null_tables() &
                            args[2]->not_null_tables()));
 
+  if (negated)
+  {
+    always_null_cache= 1;
+    if (!args[0]->is_always_null())
+      always_null_cache= args[1]->is_always_null() &&
+                         args[2]->is_always_null();
+  }
+  else
+  {
+    always_null_cache= args[0]->is_always_null() ||
+                       args[1]->is_always_null() ||
+                       args[2]->is_always_null();
+  }
   return 0;
 }
 
@@ -3545,6 +3558,23 @@ Item_func_in::fix_fields(THD *thd, Item 
   for (arg= args + 1, arg_end= args + arg_count; arg != arg_end; arg++)
     not_null_tables_cache&= (*arg)->not_null_tables();
   not_null_tables_cache|= (*args)->not_null_tables();
+  if (negated)
+  {
+    always_null_cache= 0;
+    for (arg= args, arg_end= args + arg_count;
+         !always_null_cache && arg != arg_end; arg++)
+      always_null_cache= (*arg)->is_always_null();
+  }
+  else
+  {
+    always_null_cache= 1;
+    if (!(*args)->is_always_null())
+    {
+     for (arg= args + 1, arg_end= args + arg_count; 
+          always_null_cache && arg != arg_end; arg++)
+       always_null_cache= (*arg)->is_always_null();
+    }
+  }     
   return 0;
 }
 

=== modified file 'sql/item_cmpfunc.h'
--- a/sql/item_cmpfunc.h	2009-11-16 20:49:51 +0000
+++ b/sql/item_cmpfunc.h	2010-06-29 00:24:26 +0000
@@ -239,6 +239,7 @@ public:
   longlong val_int();
   void cleanup();
   const char *func_name() const { return "<in_optimizer>"; }
+  bool is_null_preserving() const { return 0; }
   Item_cache **get_cache() { return &cache; }
   void keep_top_level_cache();
 };
@@ -438,6 +439,7 @@ public:
   longlong val_int();
   enum Functype functype() const { return NOT_ALL_FUNC; }
   const char *func_name() const { return "<not>"; }
+  bool is_null_preserving() const { return 0; }
   virtual void print(String *str, enum_query_type query_type);
   void set_sum_test(Item_sum_hybrid *item) { test_sum_item= item; };
   void set_sub_test(Item_maxmin_subselect *item) { test_sub_item= item; };
@@ -453,6 +455,7 @@ public:
   Item_func_nop_all(Item *a) :Item_func_not_all(a) {}
   longlong val_int();
   const char *func_name() const { return "<nop>"; }
+  bool is_null_preserving() const { return 0; }
   Item *neg_transformer(THD *thd);
 };
 
@@ -480,6 +483,7 @@ public:
   enum Functype rev_functype() const { return EQUAL_FUNC; }
   cond_result eq_cmp_result() const { return COND_TRUE; }
   const char *func_name() const { return "<=>"; }
+  bool is_null_preserving() const { return 0; }
   Item *neg_transformer(THD *thd) { return 0; }
 };
 
@@ -597,6 +601,7 @@ public:
   optimize_type select_optimize() const { return OPTIMIZE_KEY; }
   enum Functype functype() const   { return BETWEEN; }
   const char *func_name() const { return "between"; }
+  bool is_null_preserving() const { return !negated; }
   bool fix_fields(THD *, Item **);
   void fix_length_and_dec();
   virtual void print(String *str, enum_query_type query_type);
@@ -663,6 +668,7 @@ public:
   const char *func_name() const { return "coalesce"; }
   table_map not_null_tables() const { return 0; }
   enum_field_types field_type() const { return cached_field_type; }
+  bool is_null_preserving() const { return 0; }
 };
 
 
@@ -720,6 +726,7 @@ public:
   void fix_length_and_dec();
   uint decimal_precision() const { return args[0]->decimal_precision(); }
   const char *func_name() const { return "nullif"; }
+  bool is_null_preserving() const { return 0; }
 
   virtual inline void print(String *str, enum_query_type query_type)
   {
@@ -1152,6 +1159,7 @@ public:
   void fix_length_and_dec();
   uint decimal_precision() const;
   table_map not_null_tables() const { return 0; }
+  bool is_null_preserving() const { return 0; }
   enum Item_result result_type () const { return cached_result_type; }
   enum_field_types field_type() const { return cached_field_type; }
   const char *func_name() const { return "case"; }
@@ -1225,6 +1233,7 @@ public:
   virtual void print(String *str, enum_query_type query_type);
   enum Functype functype() const { return IN_FUNC; }
   const char *func_name() const { return " IN "; }
+  bool is_null_preserving() { return arg_count == 2 || negated; }
   bool nulls_in_row();
   bool is_bool_func() { return 1; }
   CHARSET_INFO *compare_collation() { return cmp_collation.collation; }
@@ -1275,6 +1284,7 @@ public:
     update_used_tables();
   }
   const char *func_name() const { return "isnull"; }
+  bool is_null_preserving() const { return 0; }
   /* Optimize case of not_null_column IS NULL */
   virtual void update_used_tables()
   {
@@ -1340,6 +1350,7 @@ public:
     decimals=0; max_length=1; maybe_null=0;
   }
   const char *func_name() const { return "isnotnull"; }
+  bool is_null_preserving() const { return 0; }
   optimize_type select_optimize() const { return OPTIMIZE_NULL; }
   table_map not_null_tables() const
   { return abort_on_null ? not_null_tables_cache : 0; }
@@ -1465,6 +1476,7 @@ public:
 
   enum Type type() const { return COND_ITEM; }
   List<Item>* argument_list() { return &list; }
+  bool is_null_preserving() const { return 0; }
   table_map used_tables() const;
   void update_used_tables();
   virtual void print(String *str, enum_query_type query_type);

=== modified file 'sql/item_func.cc'
--- a/sql/item_func.cc	2009-11-16 20:49:51 +0000
+++ b/sql/item_func.cc	2010-06-29 00:24:26 +0000
@@ -156,6 +156,8 @@ Item_func::fix_fields(THD *thd, Item **r
 
   used_tables_cache= not_null_tables_cache= 0;
   const_item_cache=1;
+  always_null_cache= 0;
+  bool maybe_always_null= is_null_preserving();
 
   if (check_stack_overrun(thd, STACK_MIN_SIZE, buff))
     return TRUE;				// Fatal error if flag is set!
@@ -193,6 +195,8 @@ Item_func::fix_fields(THD *thd, Item **r
       not_null_tables_cache|= item->not_null_tables();
       const_item_cache&=      item->const_item();
       with_subselect|=        item->with_subselect;
+      if (maybe_always_null && !always_null_cache)
+        always_null_cache= item->is_always_null();
     }
   }
   fix_length_and_dec();
@@ -202,7 +206,7 @@ Item_func::fix_fields(THD *thd, Item **r
   return FALSE;
 }
 
-
+ 
 bool Item_func::walk(Item_processor processor, bool walk_subquery,
                      uchar *argument)
 {
@@ -2863,6 +2867,7 @@ udf_handler::fix_fields(THD *thd, Item_r
   func->maybe_null=0;
   used_tables_cache=0;
   const_item_cache=1;
+  always_null_cache= 0;
 
   if ((f_args.arg_count=arg_count))
   {

=== modified file 'sql/item_func.h'
--- a/sql/item_func.h	2009-11-16 20:49:51 +0000
+++ b/sql/item_func.h	2010-06-29 00:24:26 +0000
@@ -40,6 +40,7 @@ public:
   uint arg_count;
   table_map used_tables_cache, not_null_tables_cache;
   bool const_item_cache;
+  bool always_null_cache;
   enum Functype { UNKNOWN_FUNC,EQ_FUNC,EQUAL_FUNC,NE_FUNC,LT_FUNC,LE_FUNC,
 		  GE_FUNC,GT_FUNC,FT_FUNC,
 		  LIKE_FUNC,ISNULL_FUNC,ISNOTNULL_FUNC,
@@ -135,7 +136,9 @@ public:
     instead.
   */
   virtual const char *func_name() const= 0;
+  virtual bool is_null_preserving() const { return TRUE; }
   virtual bool const_item() const { return const_item_cache; }
+  bool is_always_null() const { return always_null_cache; }
   inline Item **arguments() const { return args; }
   void set_arguments(List<Item> &list);
   inline uint argument_count() const { return arg_count; }
@@ -983,6 +986,7 @@ public:
   Item_func_last_insert_id(Item *a) :Item_int_func(a) {}
   longlong val_int();
   const char *func_name() const { return "last_insert_id"; }
+  bool is_null_preserving() const { return 0; }
   void fix_length_and_dec()
   {
     if (arg_count)
@@ -1034,6 +1038,7 @@ public:
   Item_udf_func(udf_func *udf_arg, List<Item> &list)
     :Item_func(list), udf(udf_arg) {}
   const char *func_name() const { return udf.name(); }
+  bool is_null_preserving() const { return 0; }
   enum Functype functype() const   { return UDF_FUNC; }
   bool fix_fields(THD *thd, Item **ref)
   {
@@ -1041,6 +1046,7 @@ public:
     bool res= udf.fix_fields(thd, this, arg_count, args);
     used_tables_cache= udf.used_tables_cache;
     const_item_cache= udf.const_item_cache;
+    always_null_cache= udf.always_null_cache;
     fixed= 1;
     return res;
   }
@@ -1352,6 +1358,7 @@ public:
   virtual void print(String *str, enum_query_type query_type);
   void print_as_stmt(String *str, enum_query_type query_type);
   const char *func_name() const { return "set_user_var"; }
+  bool is_null_preserving() const { return 0; }
   int save_in_field(Field *field, bool no_conversions,
                     bool can_use_result_field);
   int save_in_field(Field *field, bool no_conversions)
@@ -1468,6 +1475,7 @@ public:
   String* val_str(String*);
   /* TODO: fix to support views */
   const char *func_name() const { return "get_system_var"; }
+  bool is_null_preserving() const { return 0; }
   /**
     Indicates whether this system variable is written to the binlog or not.
 
@@ -1628,6 +1636,8 @@ public:
 
   const char *func_name() const;
 
+  bool is_null_preserving() const { return 0; }
+
   enum enum_field_types field_type() const;
 
   Field *tmp_table_field(TABLE *t_arg);

=== modified file 'sql/item_sum.h'
--- a/sql/item_sum.h	2009-09-15 10:46:35 +0000
+++ b/sql/item_sum.h	2010-06-29 00:24:26 +0000
@@ -287,6 +287,7 @@ public:  
   Item_sum(THD *thd, Item_sum *item);
   enum Type type() const { return SUM_FUNC_ITEM; }
   virtual enum Sumfunctype sum_func () const=0;
+  bool is_null_preserving() const { return 0; }
 
   /*
     This method is similar to add(), but it is called when the current

=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc	2009-11-27 13:20:59 +0000
+++ b/sql/sql_select.cc	2010-06-29 00:24:26 +0000
@@ -7886,6 +7886,10 @@ static COND *build_equal_items_for_cond(
   }
   else if (cond->type() == Item::FUNC_ITEM)
   {
+    Item *new_item;
+    if ((Item_func *)cond->is_always_null() && (new_item= new Item_null()))
+      return new_item;
+
     List<Item> eq_list;
     /*
       If an equality predicate forms the whole and level,

=== modified file 'sql/sql_udf.h'
--- a/sql/sql_udf.h	2007-07-06 12:18:49 +0000
+++ b/sql/sql_udf.h	2010-06-29 00:24:26 +0000
@@ -63,6 +63,7 @@ class udf_handler :public Sql_alloc
  public:
   table_map used_tables_cache;
   bool const_item_cache;
+  bool always_null_cache;
   bool not_original;
   udf_handler(udf_func *udf_arg) :u_d(udf_arg), buffers(0), error(0),
     is_null(0), initialized(0), not_original(0)

    