Re: tracking commit timestamps

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Petr Jelinek <petr(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Jaime Casanova <jaime(at)2ndquadrant(dot)com>
Subject: Re: tracking commit timestamps
Date: 2014-11-04 08:56:31
Message-ID: 20141104085631.GJ28295@alap3.anarazel.de
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On 2014-11-04 17:29:04 +0900, Michael Paquier wrote:
> On Tue, Nov 4, 2014 at 5:23 PM, Andres Freund <andres(at)2ndquadrant(dot)com>
> wrote:
>
> > On 2014-11-04 17:19:18 +0900, Michael Paquier wrote:
> > > 5) Reading the code, TransactionTreeSetCommitTimestamp is always called
> > > with do_xlog = false, making that actually no timestamps are WAL'd...
> > Hence
> > > WriteSetTimestampXlogRec is just dead code with the latest version of the
> > > patch. IMO, this should be always WAL-logged when track_commit_timestamp
> > is
> > > on.
> >
> > It's callable via a 'extern' function. So, I'd not consider it dead. And
> > the WAL logging is provided by xact.c's own WAL logging - it always does
> > the corresponding committs calls.
> >
> The code path is unused.

No. It is not. It can be called by extensions?

> We'd better make the XLOG record mandatory if
> tracking is enabled, as this information is useful on standbys as well.

Did you read what I wrote? To quote "And the WAL logging is provided by
xact.c's own WAL logging - it always does the corresponding committs
calls.".

Greetings,

Andres Freund

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

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