Обсуждение: [PATCH] Error out if SKIP LOCKED and WITH TIES are both specified

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)

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

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

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)

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)

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