To clarify, HHH-8401 is to support MySQL fractional seconds; HHH-9444 is to fix test failures due MySQL's new support for fractional seconds.
----- Original Message ----- > From: "Gail Badner" <gbad...@redhat.com> > To: "Hibernate Dev" <hibernate-dev@lists.jboss.org> > Sent: Tuesday, November 18, 2014 1:59:26 PM > Subject: MySQL fractional second precision (HHH-9444) > > MySQL support for fractional seconds in temporal values is documented in [1]: > > Prior to MySQL 5.6.4, when storing a value into a column of any temporal data > type, fractional part is discarded (truncated). When a column is defined as > TIMESTAMP(N), N indicates display width rather than fractional seconds. > > MySQL 5.6.4 and up allows enabling fractional second support by defining a > column like: TIME(n), DATETIME(n), TIMESTAMP(n), where 0 <= n <= 6. A value > of 0 indicates no fractional seconds. For compatibiliby with previous MySQL > versions, if no value for n is provided, then 0 is the default. This is > inconsistent with standard SQL, which has a default of 6. In addition, > inserting a temporal value in a column will result in rounding if the column > is defined with fewer fractional digits than the value. > > Starting from MySQL 5.6.4, there are also differences in functions that > involve temporal values. MySQL functions like NOW(), CURTIME(), SYSDATE(), > or UTC_TIMESTAMP() can optionally take an argument for fractional seconds > precision as in NOW(n), CURTIME(n), SYSDATE(n), or UTC_TIMESTAMP(n), where 0 > <= n <= 6. For compatibiliby with previous MySQL versions, if no value for n > is provided, then 0 is the default. > > I'm working on a new dialect to support fractional seconds. Since the support > for fractional seconds began in MySQL 5.6.4 it kind of complicates naming. I > assume MySQL5InnoDBDialect needs to be extended for the InnoDB engine. > > Is "MySQL564InnoDBDialect" too ugly? > > Is there any need to have a new dialect for other (non-InnoDB) MySQL engines > (e.g., MySQL564DBDialect that extends MySQL5Dialect)? > > IIUC, to be consistent with the SQL standard the default for the temporal > types in the new dialect(s) should be: > registerColumnType( Types.TIMESTAMP, "datetime(6)" ); > registerColumnType( Types.TIME, "time(6)" ); > > Is there a need the new dialect(s) to allow an application to define the > number of fractional seconds to anything other than 6? If so, would it work > to also add the following? > registerColumnType( Types.TIMESTAMP, 6, "datetime($l)" ); > registerColumnType( Types.TIME, 6, "time($l)" ); > > Also, IMO, Hibernate should render NOW(), CURTIME(), SYSDATE(), > UTC_TIMESTAMP() as NOW(6), CURTIME(6), SYSDATE(6), or UTC_TIMESTAMP(6), > respectively, unless an argument is specifically provided. > > As far as I can tell, Hibernate does not use MySQL's TIMESTAMP column type, > so I don't think anything needs to be done to support fractional seconds for > that type, or am I missing something here? > > Comments? > > Thanks, > Gail > > [1] http://dev.mysql.com/doc/refman/5.6/en/fractional-seconds.html > [2] https://hibernate.atlassian.net/browse/HHH-9444 _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
