Re:Re: Bug: WAIT FOR LSN crashes with assertion failure inside PL/pgSQL DO blocks and procedures

At 2026-04-09 20:28:16, "Alexander Korotkov" <aekorotkov(at)gmail(dot)com> wrote:
>On Thu, Apr 9, 2026 at 10:27 AM SATYANARAYANA NARLAPURAM
><satyanarlapuram(at)gmail(dot)com> wrote:
>> On Wed, Apr 8, 2026 at 11:00 PM Alexander Korotkov <aekorotkov(at)gmail(dot)com> wrote:
>>> On Thu, Apr 9, 2026 at 5:03 AM SATYANARAYANA NARLAPURAM
>>> <satyanarlapuram(at)gmail(dot)com> 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.
>>
>>
>> Agreed, attached a v2 patch with your suggestion on preventing it running
>> from procedures.
>
>Thank you. I've slightly revised your patch. I'm going to push it if
>no objections.
>
>------
>Regards,
>Alexander Korotkov

>Supabase

Hi,
This patch looks good to me overall. I spotted a typo in the commit message:

"it could pass this check causing an error elsewhere. This commit implments"

implments -> implements, missing an "e".

Regard,
Xiaopeng Wang