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help / color / mirror / Atom feedFrom: Xuneng Zhou <[email protected]>
To: Alexander Korotkov <[email protected]>
Cc: SATYANARAYANA NARLAPURAM <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: Bug: WAIT FOR LSN crashes with assertion failure inside PL/pgSQL DO blocks and procedures
Date: Thu, 9 Apr 2026 14:38:59 +0800
Message-ID: <CABPTF7WPBe4te-mzhZ3gs-iNHj+YPdTWuwaZH=63bkmO5pA+9g@mail.gmail.com> (raw)
In-Reply-To: <CAPpHfdsZ6YrzX-5uenwvw1VXuG7mpBXSOT6JFTg6aCCC0SaNEg@mail.gmail.com>
References: <CAHg+QDcN-n3NUqgRtj=BQb9fFQmH8-DeEROCr=PDbw_BBRKOYA@mail.gmail.com>
<CAPpHfdsZ6YrzX-5uenwvw1VXuG7mpBXSOT6JFTg6aCCC0SaNEg@mail.gmail.com>
On Thu, Apr 9, 2026 at 2:00 PM Alexander Korotkov <[email protected]> wrote:
>
> Hi, Satya!
>
> On Thu, Apr 9, 2026 at 5:03 AM SATYANARAYANA NARLAPURAM
> <[email protected]> wrote:
> > An assertion failure (server crash in assert-enabled builds) occurs when WAIT FOR LSN ... INTO is used inside PL/pgSQL DO blocks or within void procedures.
> >
> > Repro:
> >
> > -- Run this on a standby
> >
> > CREATE PROCEDURE test_wait()
> > LANGUAGE plpgsql AS $$
> > DECLARE
> > result text;
> > BEGIN
> > WAIT FOR LSN '0/1234' INTO result;
> > RAISE NOTICE '%', result;
> > END;
> > $$;
> > CALL test_wait();
> >
> >
> > The WAIT FOR itself succeeds, but the very next PL/pgSQL statement that requires a snapshot crashes the backend with:
> >
> > TRAP: failed Assert("portal->portalSnapshot == NULL"),
> > File: "pquery.c", Line: 1776
> >
> > Attached patches for both the test case and a potential fix. Please review.
>
> Thank you for reporting. But I doubt the fix is correct. Even that
> this particular might work OK, I don't think it's safe to release
> snapshots belonging to functions/procedures: it might affect them. I
> tend to think we must forbid wrapping WAIT FOR LSN with
> functions/procedures. I'll explore more on this today.
>
--
Best,
Xuneng
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To: [email protected]
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Subject: Re: Bug: WAIT FOR LSN crashes with assertion failure inside PL/pgSQL DO blocks and procedures
In-Reply-To: <CABPTF7WPBe4te-mzhZ3gs-iNHj+YPdTWuwaZH=63bkmO5pA+9g@mail.gmail.com>
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