Re: Parallel Seq Scan
| От | Amit Kapila |
|---|---|
| Тема | Re: Parallel Seq Scan |
| Дата | |
| Msg-id | CAA4eK1LnAGH7CfsOAsaG5H+BEG=GtOMTGSk9GWAGqu=1FLYHEg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Parallel Seq Scan (Robert Haas <robertmhaas@gmail.com>) |
| Ответы |
Re: Parallel Seq Scan
Re: Parallel Seq Scan |
| Список | pgsql-hackers |
On Fri, Mar 13, 2015 at 7:15 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Fri, Mar 13, 2015 at 7:01 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > I think this can happen if funnel->nextqueue is greater than
> > funnel->nqueues.
> > Please see if attached patch fixes the issue, else could you share the
> > scenario in more detail where you hit this issue.
>
> Speaking as the guy who wrote the first version of that code...
>
> I don't think this is the right fix; the point of that code is to
> remove a tuple queue from the funnel when it gets detached, which is a
> correct thing to want to do. funnel->nextqueue should always be less
> than funnel->nqueues; how is that failing to be the case here?
>
I could not reproduce the issue, neither the exact scenario is
>
> On Fri, Mar 13, 2015 at 7:01 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > I think this can happen if funnel->nextqueue is greater than
> > funnel->nqueues.
> > Please see if attached patch fixes the issue, else could you share the
> > scenario in more detail where you hit this issue.
>
> Speaking as the guy who wrote the first version of that code...
>
> I don't think this is the right fix; the point of that code is to
> remove a tuple queue from the funnel when it gets detached, which is a
> correct thing to want to do. funnel->nextqueue should always be less
> than funnel->nqueues; how is that failing to be the case here?
>
I could not reproduce the issue, neither the exact scenario is
mentioned in mail. However what I think can lead to funnel->nextqueue
greater than funnel->nqueues is something like below:
Assume 5 queues, so value of funnel->nqueues will be 5 and
assume value of funnel->nextqueue is 2, so now let us say 4 workers
got detached one-by-one, so for such a case it will always go in else loop
and will never change funnel->nextqueue whereas value of funnel->nqueues
will become 1.
Am I missing something?
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