Re: pgbench small bug fix

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pgbench small bug fix
Date: 2016-03-04 18:45:45
Message-ID: 20160304184545.GA727205@alvherre.pgsql
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Fabien COELHO wrote:
> >>Probably it is possible, but it will sure need more that one little
> >>condition to be achieved... I do not think that introducing a non trivial
> >>distributed election algorithm involving locks and so would be a good
> >>decision for this very little matter.
> >>
> >>My advice is "keep it simple".
> >>
> >>If this is a blocker, I can sure write such an algorithm, when I have some
> >>spare time, but I'm not sure that the purpose is worth it.
> >
> >You're probably right, but TBH I'm pretty unsure about this whole thing.
> If the question is "is there a bug", then answer is yes. The progress report
> may disappear if thread 0 happens to stop, even of all other threads go on.
> Obviously it only concerns slow queries, but there is no reason why pgbench
> should not work with slow queries. I can imagin good reason to do that, say
> to check the impact of such queries on an OLTP load.
> The bug can be kept instead, and it can be called a feature.

No, I agree that this looks like a bug and that we should fix it; for
example, if all connections from thread 0 terminate for some reason,
there will be no more reports, even if the other threads continue.
That's bad too.

What I'm unsure about is the proposed fix.

> >I will leave it alone for the time being.
> Maybe you could consider pushing the first part of the patch, which stops if
> a transaction is scheduled after the end of the run? Or is this part
> bothering you as well?

So there are *two* bugs here?

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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