Re: [EXTERNAL] Re: Add non-blocking version of PQcancel

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>
Cc: Jacob Champion <jacob(dot)champion(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Denis Laxalde <denis(dot)laxalde(at)dalibo(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, "Gregory Stark (as CFM)" <stark(dot)cfm(at)gmail(dot)com>, Jelte Fennema <Jelte(dot)Fennema(at)microsoft(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: [EXTERNAL] Re: Add non-blocking version of PQcancel
Date: 2024-03-14 10:33:30
Message-ID: 202403141033.slawmavaxujy@alvherre.pgsql
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On 2024-Mar-14, Jelte Fennema-Nio wrote:

> On Wed, 13 Mar 2024 at 20:08, Jacob Champion
> <jacob(dot)champion(at)enterprisedb(dot)com> wrote:
> > I hit this on my machine. With the attached diff I can reproduce
> > constantly (including with the most recent test patch); I think the
> > cancel must be arriving between the bind/execute steps?
>
> Nice find! Your explanation makes total sense. Attached a patchset
> that fixes/works around this issue by using the simple query protocol
> in the cancel test.

Hmm, isn't this basically saying that we're giving up on reliably
canceling queries altogether? I mean, maybe we'd like to instead fix
the bug about canceling queries in extended query protocol ...
Isn't that something you're worried about?

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"World domination is proceeding according to plan" (Andrew Morton)

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