MDEV-19906 Port show_old_temporals from MySQL 5.6

Old temporal data types (created with a pre-10.0 version of MariaDB)
are now displayed with a /* mariadb-5.3 */ comment in:

- SHOW CREATE TABLE
- DESCRIBE
- INFORMATION_SCHEMA.COLUMNS.COLUMN_TYPE

For example:

CREATE TABLE `t1` (
  `t0` datetime /* mariadb-5.3 */ DEFAULT NULL,
  `t6` datetime(6) /* mariadb-5.3 */ DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Note, new temporal data types are displayed without a format comment.

mysql-test/main/type_temporal_mariadb53.result

@@ -0,0 +1,237 @@
+#
+# MDEV-19906 Port show_old_temporals from MySQL 5.6
+#
+TRUNCATE TABLE mariadb5312_datetime;
+SHOW CREATE TABLE mariadb5312_datetime;
+Table	Create Table
+mariadb5312_datetime	CREATE TABLE `mariadb5312_datetime` (
+  `t0` datetime /* mariadb-5.3 */ DEFAULT NULL,
+  `t1` datetime(1) /* mariadb-5.3 */ DEFAULT NULL,
+  `t2` datetime(2) /* mariadb-5.3 */ DEFAULT NULL,
+  `t3` datetime(3) /* mariadb-5.3 */ DEFAULT NULL,
+  `t4` datetime(4) /* mariadb-5.3 */ DEFAULT NULL,
+  `t5` datetime(5) /* mariadb-5.3 */ DEFAULT NULL,
+  `t6` datetime(6) /* mariadb-5.3 */ DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT COLUMN_NAME, DATA_TYPE, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='mariadb5312_datetime';
+COLUMN_NAME	t0
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime /* mariadb-5.3 */
+COLUMN_NAME	t1
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime(1) /* mariadb-5.3 */
+COLUMN_NAME	t2
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime(2) /* mariadb-5.3 */
+COLUMN_NAME	t3
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime(3) /* mariadb-5.3 */
+COLUMN_NAME	t4
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime(4) /* mariadb-5.3 */
+COLUMN_NAME	t5
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime(5) /* mariadb-5.3 */
+COLUMN_NAME	t6
+DATA_TYPE	datetime
+COLUMN_TYPE	datetime(6) /* mariadb-5.3 */
+DESCRIBE mariadb5312_datetime;
+Field	t0
+Type	datetime /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t1
+Type	datetime(1) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t2
+Type	datetime(2) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t3
+Type	datetime(3) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t4
+Type	datetime(4) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t5
+Type	datetime(5) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t6
+Type	datetime(6) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+DROP TABLE mariadb5312_datetime;
+TRUNCATE TABLE mariadb5312_timestamp;
+SHOW CREATE TABLE mariadb5312_timestamp;
+Table	Create Table
+mariadb5312_timestamp	CREATE TABLE `mariadb5312_timestamp` (
+  `t0` timestamp /* mariadb-5.3 */ NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(),
+  `t1` timestamp(1) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.0',
+  `t2` timestamp(2) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.00',
+  `t3` timestamp(3) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.000',
+  `t4` timestamp(4) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.0000',
+  `t5` timestamp(5) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.00000',
+  `t6` timestamp(6) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.000000'
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT COLUMN_NAME, DATA_TYPE, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='mariadb5312_timestamp';
+COLUMN_NAME	t0
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp /* mariadb-5.3 */
+COLUMN_NAME	t1
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp(1) /* mariadb-5.3 */
+COLUMN_NAME	t2
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp(2) /* mariadb-5.3 */
+COLUMN_NAME	t3
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp(3) /* mariadb-5.3 */
+COLUMN_NAME	t4
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp(4) /* mariadb-5.3 */
+COLUMN_NAME	t5
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp(5) /* mariadb-5.3 */
+COLUMN_NAME	t6
+DATA_TYPE	timestamp
+COLUMN_TYPE	timestamp(6) /* mariadb-5.3 */
+DESCRIBE mariadb5312_timestamp;
+Field	t0
+Type	timestamp /* mariadb-5.3 */
+Null	NO
+Key	
+Default	current_timestamp()
+Extra	on update current_timestamp()
+Field	t1
+Type	timestamp(1) /* mariadb-5.3 */
+Null	NO
+Key	
+Default	0000-00-00 00:00:00.0
+Extra	
+Field	t2
+Type	timestamp(2) /* mariadb-5.3 */
+Null	NO
+Key	
+Default	0000-00-00 00:00:00.00
+Extra	
+Field	t3
+Type	timestamp(3) /* mariadb-5.3 */
+Null	NO
+Key	
+Default	0000-00-00 00:00:00.000
+Extra	
+Field	t4
+Type	timestamp(4) /* mariadb-5.3 */
+Null	NO
+Key	
+Default	0000-00-00 00:00:00.0000
+Extra	
+Field	t5
+Type	timestamp(5) /* mariadb-5.3 */
+Null	NO
+Key	
+Default	0000-00-00 00:00:00.00000
+Extra	
+Field	t6
+Type	timestamp(6) /* mariadb-5.3 */
+Null	NO
+Key	
+Default	0000-00-00 00:00:00.000000
+Extra	
+DROP TABLE mariadb5312_timestamp;
+TRUNCATE TABLE mariadb5312_time;
+SHOW CREATE TABLE mariadb5312_time;
+Table	Create Table
+mariadb5312_time	CREATE TABLE `mariadb5312_time` (
+  `t0` time /* mariadb-5.3 */ DEFAULT NULL,
+  `t1` time(1) /* mariadb-5.3 */ DEFAULT NULL,
+  `t2` time(2) /* mariadb-5.3 */ DEFAULT NULL,
+  `t3` time(3) /* mariadb-5.3 */ DEFAULT NULL,
+  `t4` time(4) /* mariadb-5.3 */ DEFAULT NULL,
+  `t5` time(5) /* mariadb-5.3 */ DEFAULT NULL,
+  `t6` time(6) /* mariadb-5.3 */ DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT COLUMN_NAME, DATA_TYPE, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='mariadb5312_time';
+COLUMN_NAME	t0
+DATA_TYPE	time
+COLUMN_TYPE	time /* mariadb-5.3 */
+COLUMN_NAME	t1
+DATA_TYPE	time
+COLUMN_TYPE	time(1) /* mariadb-5.3 */
+COLUMN_NAME	t2
+DATA_TYPE	time
+COLUMN_TYPE	time(2) /* mariadb-5.3 */
+COLUMN_NAME	t3
+DATA_TYPE	time
+COLUMN_TYPE	time(3) /* mariadb-5.3 */
+COLUMN_NAME	t4
+DATA_TYPE	time
+COLUMN_TYPE	time(4) /* mariadb-5.3 */
+COLUMN_NAME	t5
+DATA_TYPE	time
+COLUMN_TYPE	time(5) /* mariadb-5.3 */
+COLUMN_NAME	t6
+DATA_TYPE	time
+COLUMN_TYPE	time(6) /* mariadb-5.3 */
+DESCRIBE mariadb5312_time;
+Field	t0
+Type	time /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t1
+Type	time(1) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t2
+Type	time(2) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t3
+Type	time(3) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t4
+Type	time(4) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t5
+Type	time(5) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+Field	t6
+Type	time(6) /* mariadb-5.3 */
+Null	YES
+Key	
+Default	NULL
+Extra	
+DROP TABLE mariadb5312_time;

mysql-test/main/type_temporal_mariadb53.test

@@ -0,0 +1,32 @@
+--let $MYSQLD_DATADIR= `select @@datadir`
+
+--echo #
+--echo # MDEV-19906 Port show_old_temporals from MySQL 5.6
+--echo #
+
+--copy_file $MYSQL_TEST_DIR/std_data/mariadb53_temporal/mariadb5312_datetime.frm $MYSQLD_DATADIR/test/mariadb5312_datetime.frm
+TRUNCATE TABLE mariadb5312_datetime;
+SHOW CREATE TABLE mariadb5312_datetime;
+--vertical_results
+SELECT COLUMN_NAME, DATA_TYPE, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='mariadb5312_datetime';
+DESCRIBE mariadb5312_datetime;
+--horizontal_results
+DROP TABLE mariadb5312_datetime;
+
+--copy_file $MYSQL_TEST_DIR/std_data/mariadb53_temporal/mariadb5312_timestamp.frm $MYSQLD_DATADIR/test/mariadb5312_timestamp.frm
+TRUNCATE TABLE mariadb5312_timestamp;
+SHOW CREATE TABLE mariadb5312_timestamp;
+--vertical_results
+SELECT COLUMN_NAME, DATA_TYPE, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='mariadb5312_timestamp';
+DESCRIBE mariadb5312_timestamp;
+--horizontal_results
+DROP TABLE mariadb5312_timestamp;
+
+--copy_file $MYSQL_TEST_DIR/std_data/mariadb53_temporal/mariadb5312_time.frm $MYSQLD_DATADIR/test/mariadb5312_time.frm
+TRUNCATE TABLE mariadb5312_time;
+SHOW CREATE TABLE mariadb5312_time;
+--vertical_results
+SELECT COLUMN_NAME, DATA_TYPE, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='mariadb5312_time';
+DESCRIBE mariadb5312_time;
+--horizontal_results
+DROP TABLE mariadb5312_time;

sql/field.cc

@@ -5329,19 +5329,6 @@ void Field_timestamp0::sort_string(uchar *to,uint length __attribute__((unused))
 }
 
 
-void Field_timestamp::sql_type(String &res) const
-{
-  if (!decimals())
-  {
-    res.set_ascii(STRING_WITH_LEN("timestamp"));
-    return;
-  }
-  CHARSET_INFO *cs=res.charset();
-  res.length(cs->cset->snprintf(cs, (char*) res.ptr(), res.alloced_length(),
-                                "timestamp(%u)", decimals()));
-}
-
-
 int Field_timestamp0::set_time()
 {
   set_notnull();
@@ -5621,6 +5608,44 @@ void Field_temporal::set_warnings(Sql_condition::enum_warning_level trunc_level,
 }
 
 
+void Field_temporal::sql_type_dec_comment(String &res,
+                                          const Name &name,
+                                          uint dec,
+                                          const Name &comment) const
+{
+  CHARSET_INFO *cs=res.charset();
+  res.length(cs->cset->snprintf(cs, (char*) res.ptr(), res.alloced_length(),
+                                "%.*s(%u)%s%.*s%s",
+                                (uint) name.length(), name.ptr(),
+                                dec,
+                                comment.length() ? " /* " : "",
+                                (uint) comment.length(), comment.ptr(),
+                                comment.length() ? " */" : ""));
+}
+
+
+void Field_temporal::sql_type_comment(String &res,
+                                      const Name &name,
+                                      const Name &comment) const
+{
+  CHARSET_INFO *cs=res.charset();
+  res.length(cs->cset->snprintf(cs, (char*) res.ptr(), res.alloced_length(),
+                                "%.*s%s%.*s%s",
+                                (uint) name.length(), name.ptr(),
+                                comment.length() ? " /* " : "",
+                                (uint) comment.length(), comment.ptr(),
+                                comment.length() ? " */" : ""));
+}
+
+
+const Name & Field_temporal::type_version_mysql56()
+{
+  DBUG_EXECUTE_IF("sql_type", return Type_handler::version_mysql56(); );
+  static Name none(NULL, 0);
+  return none;
+}
+
+
 /*
   Store string into a date/time field
 
@@ -5991,17 +6016,6 @@ void Field_time0::sort_string(uchar *to,uint length __attribute__((unused)))
   to[2] = ptr[0];
 }
 
-void Field_time::sql_type(String &res) const
-{
-  if (decimals() == 0)
-  {
-    res.set_ascii(STRING_WITH_LEN("time"));
-    return;
-  }
-  CHARSET_INFO *cs= res.charset();
-  res.length(cs->cset->snprintf(cs, (char*) res.ptr(), res.alloced_length(),
-                               "time(%d)", decimals()));
-}
 
 int Field_time_hires::reset()
 {
@@ -6811,19 +6825,6 @@ void Field_datetime0::sort_string(uchar *to,uint length __attribute__((unused)))
 }
 
 
-void Field_datetime::sql_type(String &res) const
-{
-  if (decimals() == 0)
-  {
-    res.set_ascii(STRING_WITH_LEN("datetime"));
-    return;
-  }
-  CHARSET_INFO *cs= res.charset();
-  res.length(cs->cset->snprintf(cs, (char*) res.ptr(), res.alloced_length(),
-                                "datetime(%u)", decimals()));
-}
-
-
 int Field_datetime::set_time()
 {
   THD *thd= table->in_use;

sql/field.h

@@ -2938,6 +2938,22 @@ protected:
     set_warnings(level, str, MYSQL_TIME_WARN_TRUNCATED, typestr);
     return 1;
   }
+  void sql_type_comment(String &str,
+                        const Name &name,
+                        const Name &comment) const;
+  void sql_type_dec_comment(String &str,
+                            const Name &name, uint dec,
+                            const Name &comment) const;
+  void sql_type_opt_dec_comment(String &str,
+                                const Name &name, uint dec,
+                                const Name &comment) const
+  {
+    if (dec)
+      sql_type_dec_comment(str, name, dec, comment);
+    else
+      sql_type_comment(str, name, comment);
+  }
+  static const Name &type_version_mysql56();
 public:
   Field_temporal(uchar *ptr_arg,uint32 len_arg, uchar *null_ptr_arg,
                  uchar null_bit_arg, utype unireg_check_arg,
@@ -3068,7 +3084,6 @@ public:
   int  save_in_field(Field *to) override;
   longlong val_int() override;
   String *val_str(String *, String *) override;
-  void sql_type(String &str) const override;
   bool zero_pack() const override { return false; }
   /*
     This method is used by storage/perfschema and
@@ -3110,6 +3125,11 @@ public:
   { }
   enum ha_base_keytype key_type() const override
   { return HA_KEYTYPE_ULONG_INT; }
+  void sql_type(String &str) const override
+  {
+    sql_type_comment(str, Field_timestamp0::type_handler()->name(),
+                     Type_handler::version_mariadb53());
+  }
   double val_real() override
   {
     return (double) Field_timestamp0::val_int();
@@ -3193,6 +3213,11 @@ public:
   {
     DBUG_ASSERT(dec);
   }
+  void sql_type(String &str) const override
+  {
+    sql_type_dec_comment(str, Field_timestamp_hires::type_handler()->name(),
+                         dec, Type_handler::version_mariadb53());
+  }
   bool val_native(Native *to) override;
   my_time_t get_timestamp(const uchar *pos, ulong *sec_part) const override;
   int cmp(const uchar *,const uchar *) const override;
@@ -3219,6 +3244,12 @@ public:
   { return &type_handler_timestamp2; }
   enum_field_types binlog_type() const override
   { return MYSQL_TYPE_TIMESTAMP2; }
+  void sql_type(String &str) const override
+  {
+    sql_type_opt_dec_comment(str, Field_timestampf::type_handler()->name(),
+                             dec, type_version_mysql56());
+
+  }
   enum_conv_type rpl_conv_type_from(const Conv_source &source,
                                     const Relay_log_info *rli,
                                     const Conv_param &param) const override;
@@ -3455,7 +3486,6 @@ public:
   int  store_decimal(const my_decimal *) override;
   String *val_str(String *, String *) override;
   bool send_binary(Protocol *protocol) override;
-  void sql_type(String &str) const override;
   void set_curdays(THD *thd);
   Field *new_key_field(MEM_ROOT *root, TABLE *new_table,
                        uchar *new_ptr, uint32 length,
@@ -3477,6 +3507,11 @@ public:
                 unireg_check_arg, field_name_arg)
   { }
   enum ha_base_keytype key_type() const override { return HA_KEYTYPE_INT24; }
+  void sql_type(String &str) const override
+  {
+    sql_type_comment(str, Field_time0::type_handler()->name(),
+                     Type_handler::version_mariadb53());
+  }
   double val_real() override;
   longlong val_int() override;
   bool get_date(MYSQL_TIME *ltime, date_mode_t fuzzydate) override;
@@ -3532,6 +3567,11 @@ public:
     zero_point= sec_part_shift(
                    ((TIME_MAX_VALUE_SECONDS+1LL)*TIME_SECOND_PART_FACTOR), dec);
   }
+  void sql_type(String &str) const override
+  {
+    sql_type_dec_comment(str, Field_time_hires::type_handler()->name(),
+                         dec, Type_handler::version_mariadb53());
+  }
   int reset() override;
   bool get_date(MYSQL_TIME *ltime, date_mode_t fuzzydate) override;
   int cmp(const uchar *,const uchar *) const override;
@@ -3560,6 +3600,11 @@ public:
   const Type_handler *type_handler() const override
   { return &type_handler_time2; }
   enum_field_types binlog_type() const override { return MYSQL_TYPE_TIME2; }
+  void sql_type(String &str) const override
+  {
+    sql_type_opt_dec_comment(str, Field_timef::type_handler()->name(),
+                             dec, type_version_mysql56());
+  }
   enum_conv_type rpl_conv_type_from(const Conv_source &source,
                                     const Relay_log_info *rli,
                                     const Conv_param &param) const override;
@@ -3616,7 +3661,6 @@ public:
   int  store(longlong nr, bool unsigned_val) override;
   int  store_time_dec(const MYSQL_TIME *ltime, uint dec) override;
   int  store_decimal(const my_decimal *) override;
-  void sql_type(String &str) const override;
   int set_time() override;
   Item *get_equal_const_item(THD *thd, const Context &ctx, Item *const_item)
     override
@@ -3640,6 +3684,11 @@ public:
   {}
   enum ha_base_keytype key_type() const override
   { return HA_KEYTYPE_ULONGLONG; }
+  void sql_type(String &str) const override
+  {
+    sql_type_comment(str, Field_datetime0::type_handler()->name(),
+                     Type_handler::version_mariadb53());
+  }
   double val_real() override
   {
     return (double) Field_datetime0::val_int();
@@ -3719,6 +3768,11 @@ public:
   {
     DBUG_ASSERT(dec);
   }
+  void sql_type(String &str) const override
+  {
+    sql_type_dec_comment(str, Field_datetime_hires::type_handler()->name(),
+                         dec, Type_handler::version_mariadb53());
+  }
   int cmp(const uchar *,const uchar *) const override;
   uint32 pack_length() const override
   { return Type_handler_datetime::hires_bytes(dec); }
@@ -3746,6 +3800,11 @@ public:
   { return &type_handler_datetime2; }
   enum_field_types binlog_type() const override
   { return MYSQL_TYPE_DATETIME2; }
+  void sql_type(String &str) const override
+  {
+    sql_type_opt_dec_comment(str, Field_datetimef::type_handler()->name(),
+                             dec, type_version_mysql56());
+  }
   enum_conv_type rpl_conv_type_from(const Conv_source &source,
                                     const Relay_log_info *rli,
                                     const Conv_param &param) const override;

sql/sql_show.cc

@@ -2116,12 +2116,6 @@ int show_create_table(THD *thd, TABLE_LIST *table_list, String *packet,
     field->sql_type(type);
     packet->append(type.ptr(), type.length(), system_charset_info);
 
-    DBUG_EXECUTE_IF("sql_type",
-                    packet->append(" /* ");
-                    packet->append(field->type_handler()->version().ptr());
-                    packet->append(" */");
-                    );
-
     if (field->has_charset() && !(sql_mode & (MODE_MYSQL323 | MODE_MYSQL40)))
     {
       if (field->charset() != share->table_charset)

sql/sql_type.cc

@@ -1469,13 +1469,13 @@ const Name Type_handler::version() const
   return ver;
 }
 
-const Name Type_handler::version_mariadb53() const
+const Name & Type_handler::version_mariadb53()
 {
   static const Name ver(STRING_WITH_LEN("mariadb-5.3"));
   return ver;
 }
 
-const Name Type_handler::version_mysql56() const
+const Name & Type_handler::version_mysql56()
 {
   static const Name ver(STRING_WITH_LEN("mysql-5.6"));
   return ver;
@@ -3986,9 +3986,9 @@ Field *Type_handler_datetime_common::make_schema_field(MEM_ROOT *root,
                                                        bool show_field) const
 {
   LEX_CSTRING name= def.name();
-  return new_Field_datetime(root,
+  return new (root) Field_datetimef(addr.ptr(),
-                            addr.ptr(), addr.null_ptr(), addr.null_bit(),
+                                    addr.null_ptr(), addr.null_bit(),
-                            Field::NONE, &name, def.fsp());
+                                    Field::NONE, &name, def.fsp());
 }
 
 

sql/sql_type.h

@@ -3326,8 +3326,6 @@ class Type_handler
 {
   Name m_name;
 protected:
-  const Name version_mysql56() const;
-  const Name version_mariadb53() const;
   String *print_item_value_csstr(THD *thd, Item *item, String *str) const;
   String *print_item_value_temporal(THD *thd, Item *item, String *str,
                                      const Name &type_name, String *buf) const;
@@ -3390,6 +3388,8 @@ public:
   static void partition_field_type_not_allowed(const LEX_CSTRING &field_name);
   static bool partition_field_check_result_type(Item *item,
                                                 Item_result expected_type);
+  static const Name & version_mysql56();
+  static const Name & version_mariadb53();
 
   void set_name(Name n) { DBUG_ASSERT(!m_name.ptr()); m_name= n; }
   const Name name() const { return m_name; }