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help / color / mirror / Atom feedFrom: Alexander Lakhin <[email protected]>
To: Michael Paquier <[email protected]>
To: [email protected]
Subject: Re: BUG #19494: Error on transaction commit inside pipeline triggers psql's Assert
Date: Fri, 29 May 2026 07:00:01 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
<[email protected]>
<[email protected]>
Hello Michael,
28.05.2026 08:26, Michael Paquier wrote:
> On Thu, May 28, 2026 at 12:51:38PM +0900, Michael Paquier wrote:
>> I am completely sure yet, but it looks like we will need to be smarter
>> with the handling of the number of piped commands by tracking them
>> across the syncs in the shape of a queue, or something like that? So
>> it feels like we need to think harder about the tracking of this
>> activity depending on the state of the pipeline we're in. Or we could
>> lift some of these assertions, but that would not be right to me.
> Hmm. Taking a step back this would be overcomplicating things. As
> long as we are careful to consume the synced results still in a
> pipeline, it looks like we should be fine. While digging into it, I
> have found a third assertion that was triggerable with
> available_results at the end of the pipeline, once I began mixing
> \getresults with a deferred error.
>
> This stuff is tricky enough that I may not have overseen all the
> patterns possible, of course, at least this is progress.
>
> Alexander, what do you think?
While testing the patch, I've observed apparently new anomaly. psql got
stuck inside this loop:
if (end_pipeline)
{
/*
* Reset available/requested results. Normally these are already 0,
* but an error generated by Sync processing itself can leave some of
* them behind. Consume them before exiting pipeline mode.
*/
while (pset.piped_syncs > 0)
{
PGresult *remaining = PQgetResult(pset.db);
if (remaining == NULL)
continue;
...
}
it's happening upon/after postgres process termination, so PQgetResult()
returns NULL, pset.piped_syncs == 1. I need more time to look deeper and
to come with a reproducer, but maybe you can already see what's wrong.
Best regards,
Alexander
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Subject: Re: BUG #19494: Error on transaction commit inside pipeline triggers psql's Assert
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