From: Tom Lane <tgl@sss.pgh.pa.us>
To: Noah Misch <noah@leadboat.com>
Cc: Francesco Degrassi <francesco.degrassi@optionfactory.net>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: Leader backend hang on IPC/ParallelFinish when LWLock held at parallel query start
Date: Thu, 07 Nov 2024 14:29:19 -0500
Message-ID: <3459938.1731007759@sss.pgh.pa.us> (raw)
In-Reply-To: <20241107192233.94.nmisch@google.com>
References: <CAC-SaSzHUKT=vZJ8MPxYdC_URPfax+yoA1hKTcF4ROz_Q6z0_Q@mail.gmail.com>
<20240918030159.2a.nmisch@google.com>
<1737570.1726633422@sss.pgh.pa.us>
<20240918050434.13.nmisch@google.com>
<3441950.1730999841@sss.pgh.pa.us>
<20241107192233.94.nmisch@google.com>
Noah Misch <noah@leadboat.com> writes:
> On Thu, Nov 07, 2024 at 12:17:21PM -0500, Tom Lane wrote:
>> While working on the release notes, I noticed that nothing further
>> got done about this concern. What do you think of adding a test
>> somewhere early in executor startup, to the effect of
>>
>> if (!INTERRUPTS_CAN_BE_PROCESSED())
>> ereport(ERROR,
>> (errmsg("cannot start a query with interrupts disabled")));
>>
>> It's definitely a band-aid, but it seems better than leaving
>> things at the status quo.
> That would fire in queries that don't error or hang today, so I think that
> would be worse than the status quo.
Good point.
> This thread's previous commit just forced a serial plan.
My concern is that the previous commit forced new plans to be serial,
but did nothing about re-use of an existing plan.
> The executor
> counterpart would look like having the executor do what it does when there are
> no free worker slots.
Ah, that could be a way out. Stick an INTERRUPTS_CAN_BE_PROCESSED()
call somewhere in there? That could even allow us to revert the
planner change, which would simplify testing of the executor change.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, noah@leadboat.com, francesco.degrassi@optionfactory.net, pgsql-bugs@lists.postgresql.org
Subject: Re: Leader backend hang on IPC/ParallelFinish when LWLock held at parallel query start
In-Reply-To: <3459938.1731007759@sss.pgh.pa.us>
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