Re: tracking commit timestamps

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Petr Jelinek <petr(at)2ndquadrant(dot)com>, Steve Singer <steve(at)ssinger(dot)info>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Anssi Kääriäinen <anssi(dot)kaariainen(at)thl(dot)fi>, 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: 2014-11-25 13:35:04
Message-ID: CAHGQGwFybprq5=27szFJcCjzT7ZzpV7RgRotQS+hXFd8xyW_Ww@mail.gmail.com
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On Tue, Nov 25, 2014 at 7:58 AM, Alvaro Herrera
<alvherre(at)2ndquadrant(dot)com> wrote:
>> And here is v10 which fixes conflicts with Heikki's WAL API changes (no
>> changes otherwise).
>
> After some slight additional changes, here's v11, which I intend to
> commit early tomorrow. The main change is moving the test module from
> contrib to src/test/modules.

When I specify the XID of the aborted transaction in pg_xact_commit_timestamp(),
it always returns 2000-01-01 09:00:00+09. Is this intentional?

Can I check my understanding? Probably we cannot use this feature to calculate
the actual replication lag by, for example, comparing the result of
pg_last_committed_xact() in the master and that of
pg_last_xact_replay_timestamp()
in the standby. Because pg_last_xact_replay_timestamp() can return even
the timestamp of aborted transaction, but pg_last_committed_xact()
cannot. Right?

Regards,

--
Fujii Masao

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