Re: transction_timestamp() inside of procedures

From: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Michael Paquier <michael(at)paquier(dot)xyz>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: transction_timestamp() inside of procedures
Date: 2018-09-26 21:48:00
Message-ID: ec816bd0-0357-23a9-bea2-3ef1619eb340@2ndquadrant.com
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On 26/09/2018 17:54, Alvaro Herrera wrote:
> What could be the use for the transaction timestamp? I think one of the
> most important uses (at least in pg_stat_activity) is to verify that
> transactions are not taking excessively long time to complete; that's
> known to cause all sorts of trouble in Postgres, and probably other
> DBMSs too. If we don't accurately measure what it really is, and
> instead keep the compatibility behavior, we risk panicking people
> because they think some transaction has been running for a long time
> when in reality it's just a very long procedure which commits frequently
> enough not to be a problem.

That's certainly a good argument. Note that if we implemented that the
transaction timestamp is advanced inside procedures, that would also
mean that the transaction timestamp as observed in pg_stat_activity
would move during VACUUM, for example. That might or might not be
desirable.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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