On 1/25/2007 6:49 PM, Tom Lane wrote:
Jan Wieck <[EMAIL PROTECTED]> writes:
To provide this data, I would like to add another "log" directory, pg_tslog. The files in this directory will be similar to the clog, but contain arrays of timestamptz values.


Why should everybody be made to pay this overhead?

It could be made an initdb time option. If you intend to use a product that requires this feature, you will be willing to pay that price.


The COMMIT syntax will get extended to
    COMMIT [TRANSACTION] [WITH TIMESTAMP <timestamptz>];
The extension is limited to superusers and will override the normally generated commit timestamp. This will be used to give the replicating transaction on the replica the exact same timestamp it got on the originating master node.

I'm not convinced you've even thought this through.  If you do that then
you have no guarantee of commit timestamp monotonicity on the slave
(if it has either multi masters or any locally generated transactions).
Since this is supposedly for a multi-master system, that seems a rather
fatal objection --- no node in the system will actually have commit
timestamp monotonicity.  What are you hoping to accomplish with this?

Maybe I wasn't clear enough about this. If the commit timestamps on the local machine are guaranteed to increase at least by one millisecond (okay that limits the system to a sustained 1000 commits per second before it really seems to run ahead of time), then no two commits on the same instance will ever have the same timestamp. If furthermore each instance in a cluster has a distinct priority (the microsecond part added to the millisecond-truncated timestamp), each commit timestamp could even act as a globally unique ID. It does require that all the nodes in the cluster are configured with a distinct priority.

What I hope to accomplish with this is a very easy, commit time based "last update wins" conflict resolution for data fields of the overwrite nature.

The replication system I have in mind will have another field type of the balance nature, where it will never communicate the current value but only deltas that get applied regardless of the two timestamps.


Jan

--
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#================================================== [EMAIL PROTECTED] #

---------------------------(end of broadcast)---------------------------
TIP 3: Have you checked our extensive FAQ?

              http://www.postgresql.org/docs/faq

Reply via email to