Re: tracking commit timestamps

On 11 November 2014 16:19, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2014-11-11 16:10:47 +0000, Simon Riggs wrote:
>> On 4 November 2014 08:23, Andres Freund <andres@2ndquadrant.com> wrote:
>>
>> >> 6) Shouldn't any value update of track_commit_timestamp be tracked in
>> >> XLogReportParameters? That's thinking about making the commit timestamp
>> >> available on standbys as well..
>> >
>> > Yes, it should.
>>
>> Agree committs should be able to run on standby, but it seems possible
>> to do that without it running on the master.
>
> I don't think that's realistic. It requires WAL to be written in some
> cases, so that's not going to work. I also don't think it's a
> particularly interesting ability?

OK, so we are saying commit timestamp will NOT be available on Standbys.

I'm fine with that, since data changes aren't generated there.


> So it works correctly. We're currently truncating the slru on startup
> when the guc is disabled which would cause problems WAL records coming
> in from the primary. I think the code also needs some TLC to correctly
> work after a failover.

OK

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services