MIME-Version: 1.0
References: <93fb937f-9f4d-4bd7-b7e6-51d5f98859d9@posteo.de>
 <14506.1770844674@sss.pgh.pa.us> <b461c689-1d2a-4e20-be33-e75a439d5823@posteo.de>
 <101916.1770850197@sss.pgh.pa.us> <777cfa1c-fd1f-479f-b9b8-217b0f7a40b7@posteo.de>
 <87ca8c2c-6826-44d1-8a31-a5f793a2729e@posteo.de>
In-Reply-To: <87ca8c2c-6826-44d1-8a31-a5f793a2729e@posteo.de>
From: Greg Sabino Mullane <htamfids@gmail.com>
Date: Tue, 17 Feb 2026 09:55:30 -0500
Message-ID: <CAKAnmmJoX=KJyH2g8tWtbSoqJp7nnyeBChaLgF6bbGv1zGLzwg@mail.gmail.com>
Subject: Re: Guarantee order of batched pg_advisory_xact_lock
To: Nico Heller <nico.heller@posteo.de>
Cc: pgsql-general@postgresql.org
Content-Type: multipart/alternative; boundary="000000000000595cf1064b064582"
Archived-At: <https://www.postgresql.org/message-id/CAKAnmmJoX%3DKJyH2g8tWtbSoqJp7nnyeBChaLgF6bbGv1zGLzwg%40mail.gmail.com>
Precedence: bulk

--000000000000595cf1064b064582
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Mon, Feb 16, 2026 at 12:45=E2=80=AFPM Nico Heller <nico.heller@posteo.de=
> wrote:

> Does anyone have any idea what the root cause of my issue is? I appreciat=
e
> any insight.
> As I said, hash collisions can be rules out, sadly.
>

Well, you could set log_statement to 'all' for a bit to see *exactly* what
each of the deadlocking processes are doing. Alternatively, perhaps you can
write a hashextendedkey() function that outputs arguments and results to a
log and/or a table.

keysToLock is a text[] parameter which is pre-sorted in our application


Would not hurt to triple-check this part as well. Could show us the app
code? Maybe put in some sort of global assert in the app to verify that
things are indeed sorted as you think they are.


Cheers,
Greg

--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support

--000000000000595cf1064b064582
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div dir=3D"ltr"><div>On Mon, Feb 16, 2026 at 12:45=E2=80=
=AFPM Nico Heller &lt;<a href=3D"mailto:nico.heller@posteo.de">nico.heller@=
posteo.de</a>&gt; wrote:</div></div><div class=3D"gmail_quote gmail_quote_c=
ontainer"><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8=
ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>

 =20
   =20
 =20
  <div>
    <p>Does anyone have any idea what the root cause of my issue is? I
      appreciate any insight.<br>
      As I said, hash collisions can be rules out, sadly.</p></div></blockq=
uote><div><br></div><div>Well, you could set log_statement to &#39;all&#39;=
 for a bit to see *exactly* what each of the deadlocking processes are doin=
g. Alternatively, perhaps you can write a hashextendedkey() function that o=
utputs arguments and results to a log and/or a table.<div><br></div><blockq=
uote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1p=
x solid rgb(204,204,204);padding-left:1ex">keysToLock is a text[] parameter=
 which is pre-sorted in our application</blockquote><div><br></div></div><d=
iv>Would not hurt to triple-check this part as well. Could show us the app =
code? Maybe put in some sort of global assert in the app to verify that thi=
ngs are indeed sorted as you think they are.</div><div><br></div><div><br><=
/div><div>Cheers,</div></div><div dir=3D"ltr" class=3D"gmail_signature"><di=
v dir=3D"ltr"><div>Greg</div><div><br></div><div>--</div><div>Crunchy Data =
- <a href=3D"https://www.crunchydata.com" target=3D"_blank">https://www.cru=
nchydata.com</a></div><div>Enterprise Postgres Software Products &amp; Tech=
 Support</div><div><br></div></div></div></div>

--000000000000595cf1064b064582--