From: Tom Lane <tgl@sss.pgh.pa.us>
To: Noah Misch <noah@leadboat.com>
cc: Francesco Degrassi <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: <20240918050434.13.nmisch@google.com>
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 <20240918050434.13.nmisch@google.com>
Comments: In-reply-to Noah Misch <noah@leadboat.com>
	message dated "Tue, 17 Sep 2024 22:04:34 -0700"
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Date: Thu, 07 Nov 2024 12:17:21 -0500
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Noah Misch <noah@leadboat.com> writes:
> On Wed, Sep 18, 2024 at 12:23:42AM -0400, Tom Lane wrote:
>> I do not have much faith in this patch.  It assumes that the
>> condition "interrupts can be processed" is the same at plan time and
>> execution time.  For plans extracted from the plan cache, there seems
>> little reason to assume that must be true.  The proposed test case
>> cannot trigger that (today anyway) because SQL-language functions
>> don't deal in cached plans, but I suspect it could be broken with a
>> test case using a plpgsql function instead.

> Good point.  I missed that.

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.

			regards, tom lane