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  1. Error out if SKIP LOCKED and WITH TIES are both specified

  1. [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    David Christensen <david.christensen@crunchydata.com> — 2021-08-13T16:16:18Z

    Both bugs #16676[1] and #17141[2] illustrate that the combination of SKIP
LOCKED and FETCH FIRST
WITH TIES break expectations when it comes to rows returned to other
sessions accessing the same
row.  Since this situation is detectable from the syntax and hard to fix
otherwise, forbid for now,
with the potential to fix in the future.

[1]
https://www.postgresql.org/message-id/16676-fd62c3c835880da6%40postgresql.org
[2]
https://www.postgresql.org/message-id/17141-913d78b9675aac8e%40postgresql.org

Proposed backpatch to 13.

  2. Re: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    Alvaro Herrera <alvherre@alvh.no-ip.org> — 2021-08-30T20:51:27Z

    On 2021-Aug-13, David Christensen wrote:

> Both bugs #16676[1] and #17141[2] illustrate that the combination of
> SKIP LOCKED and FETCH FIRST WITH TIES break expectations when it comes
> to rows returned to other sessions accessing the same row.  Since this
> situation is detectable from the syntax and hard to fix otherwise,
> forbid for now, with the potential to fix in the future.

I think we should do this, given that it has show potential to bite
people.  We should also add a small mentioned to this in the docs, as in
the attached.

What do others think?

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/
"Escucha y olvidarás; ve y recordarás; haz y entenderás" (Confucio)

  3. Re: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    David Christensen <david.christensen@crunchydata.com> — 2021-08-30T20:55:10Z

    On Mon, Aug 30, 2021 at 3:51 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>
> On 2021-Aug-13, David Christensen wrote:
>
> > Both bugs #16676[1] and #17141[2] illustrate that the combination of
> > SKIP LOCKED and FETCH FIRST WITH TIES break expectations when it comes
> > to rows returned to other sessions accessing the same row.  Since this
> > situation is detectable from the syntax and hard to fix otherwise,
> > forbid for now, with the potential to fix in the future.
>
> I think we should do this, given that it has show potential to bite
> people.  We should also add a small mentioned to this in the docs, as in
> the attached.
>
> What do others think?

The patch I included had a doc mention in roughly the same place (at
least the same file), but I'm not tied to the wording I used (and I
may have missed more than one spot that might be appropriate).  In any
case, +1.

David

  4. Re: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    Michael Paquier <michael@paquier.xyz> — 2021-10-01T06:47:43Z

    On Mon, Aug 30, 2021 at 03:55:10PM -0500, David Christensen wrote:
> On Mon, Aug 30, 2021 at 3:51 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>> I think we should do this, given that it has show potential to bite
>> people.  We should also add a small mentioned to this in the docs, as in
>> the attached.
>>
>> What do others think?

There is a CF entry for this patch:
https://commitfest.postgresql.org/34/3286/

Alvaro, are you planning to wrap that?
--
Michael

  5. Re: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    Alvaro Herrera <alvherre@alvh.no-ip.org> — 2021-10-01T12:55:02Z

    On 2021-Oct-01, Michael Paquier wrote:

> On Mon, Aug 30, 2021 at 03:55:10PM -0500, David Christensen wrote:
> > On Mon, Aug 30, 2021 at 3:51 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >> I think we should do this, given that it has show potential to bite
> >> people.  We should also add a small mentioned to this in the docs, as in
> >> the attached.
> >>
> >> What do others think?
> 
> There is a CF entry for this patch:
> https://commitfest.postgresql.org/34/3286/
> 
> Alvaro, are you planning to wrap that?

I've had mixed feelings about this whole idea, but I think it's the
right thing to do.  I'll try to get it pushed today.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/
"I can't go to a restaurant and order food because I keep looking at the
fonts on the menu.  Five minutes later I realize that it's also talking
about food" (Donald Knuth)

  6. Re: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    Alvaro Herrera <alvherre@alvh.no-ip.org> — 2021-10-01T21:33:01Z

    On 2021-Aug-13, David Christensen wrote:

> Both bugs #16676[1] and #17141[2] illustrate that the combination of
> SKIP LOCKED and FETCH FIRST WITH TIES break expectations when it comes
> to rows returned to other sessions accessing the same row.  Since this
> situation is detectable from the syntax and hard to fix otherwise,
> forbid for now, with the potential to fix in the future.

Thank you, pushed with minimal adjustment.

-- 
Álvaro Herrera           39°49'30"S 73°17'W  —  https://www.EnterpriseDB.com/
"Digital and video cameras have this adjustment and film cameras don't for the
same reason dogs and cats lick themselves: because they can."   (Ken Rockwell)

  7. Re: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

    Jaime Casanova <jcasanov@systemguards.com.ec> — 2021-10-02T17:24:18Z

    On Fri, Oct 01, 2021 at 06:33:01PM -0300, Alvaro Herrera wrote:
> On 2021-Aug-13, David Christensen wrote:
> 
> > Both bugs #16676[1] and #17141[2] illustrate that the combination of
> > SKIP LOCKED and FETCH FIRST WITH TIES break expectations when it comes
> > to rows returned to other sessions accessing the same row.  Since this
> > situation is detectable from the syntax and hard to fix otherwise,
> > forbid for now, with the potential to fix in the future.
> 
> Thank you, pushed with minimal adjustment.
> 

BTW, I just marked this one as committed in CF app

-- 
Jaime Casanova
Director de Servicios Profesionales
SystemGuards - Consultores de PostgreSQL