| Lists: | pgsql-hackers |
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| From: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
|---|---|
| To: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | How to prohibit parallel scan through tableam? |
| Date: | 2019-11-27 11:33:42 |
| Message-ID: | fafd6dae-0342-5a3c-c040-7828f5a595fb@postgrespro.ru |
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| Lists: | pgsql-hackers |
Hi hackers,
I wonder how it is possible to prohibit parallel scan for the external
storage accessed through tableam?
For example if I want to implement specialized tableam for fast access
to temp tables, how can I inform optimizer that
parallel scan is not possible (because table data is local to the backend)?
Thanks in advance,
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
| From: | Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com> |
|---|---|
| To: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: How to prohibit parallel scan through tableam? |
| Date: | 2019-11-27 12:12:35 |
| Message-ID: | CA+FpmFeV4XH0du_60F5wKnoGku-fM_kACpRdMMTDLkYqePF3WA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, 27 Nov 2019 at 12:33, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
wrote:
> Hi hackers,
>
> I wonder how it is possible to prohibit parallel scan for the external
> storage accessed through tableam?
> For example if I want to implement specialized tableam for fast access
> to temp tables, how can I inform optimizer that
> parallel scan is not possible (because table data is local to the backend)?
>
> How about setting parallel_setup_cost to disable_cost in costsize.c for
your specific scan method.
--
Regards,
Rafia Sabih
| From: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
|---|---|
| To: | pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: How to prohibit parallel scan through tableam? |
| Date: | 2019-11-27 13:10:20 |
| Message-ID: | fb63b86e-f862-b6f9-b321-360ad11172a6@postgrespro.ru |
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| Lists: | pgsql-hackers |
On 27.11.2019 15:12, Rafia Sabih wrote:
>
>
> On Wed, 27 Nov 2019 at 12:33, Konstantin Knizhnik
> <k(dot)knizhnik(at)postgrespro(dot)ru <mailto:k(dot)knizhnik(at)postgrespro(dot)ru>> wrote:
>
> Hi hackers,
>
> I wonder how it is possible to prohibit parallel scan for the
> external
> storage accessed through tableam?
> For example if I want to implement specialized tableam for fast
> access
> to temp tables, how can I inform optimizer that
> parallel scan is not possible (because table data is local to the
> backend)?
>
> How about setting parallel_setup_cost to disable_cost in costsize.c
> for your specific scan method.
How can I do it if i just implementing my AM and not going to change any
postgres code?
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
| From: | Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com> |
|---|---|
| To: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: How to prohibit parallel scan through tableam? |
| Date: | 2019-11-28 13:23:21 |
| Message-ID: | CA+FpmFf+PVYz4t1U1iKxEbRhZtGV+FfgSx2TTnkNWrn43wvaMg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, 27 Nov 2019 at 12:33, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
wrote:
> Hi hackers,
>
> I wonder how it is possible to prohibit parallel scan for the external
> storage accessed through tableam?
> For example if I want to implement specialized tableam for fast access
> to temp tables, how can I inform optimizer that
> parallel scan is not possible (because table data is local to the backend)?
>
> One moment, isn't that parallel scans are already restricted for temp
tables, or I have misunderstood something here...?
--
Regards,
Rafia Sabih
| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: How to prohibit parallel scan through tableam? |
| Date: | 2019-12-03 21:22:17 |
| Message-ID: | 20191203212217.lxqvnffiw5n5thzy@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2019-11-27 14:33:42 +0300, Konstantin Knizhnik wrote:
> I wonder how it is possible to prohibit parallel scan for the external
> storage accessed through tableam?
> For example if I want to implement specialized tableam for fast access to
> temp tables, how can I inform optimizer that
> parallel scan is not possible (because table data is local to the backend)?
I don't think there currently is a good way to do so - but it shouldn't
be hard to add that capability.
Greetings,
Andres Freund
| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: How to prohibit parallel scan through tableam? |
| Date: | 2019-12-03 21:24:14 |
| Message-ID: | 20191203212414.qp4s2wljeodaz3xu@alap3.anarazel.de |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Lists: | 503 윈 토토 페치 실패 |
Hi,
On 2019-11-27 16:10:20 +0300, Konstantin Knizhnik wrote:
> On 27.11.2019 15:12, Rafia Sabih wrote:
> > On Wed, 27 Nov 2019 at 12:33, Konstantin Knizhnik
> > <k(dot)knizhnik(at)postgrespro(dot)ru <mailto:k(dot)knizhnik(at)postgrespro(dot)ru>> wrote:
> >
> > Hi hackers,
> >
> > I wonder how it is possible to prohibit parallel scan for the
> > external
> > storage accessed through tableam?
> > For example if I want to implement specialized tableam for fast
> > access
> > to temp tables, how can I inform optimizer that
> > parallel scan is not possible (because table data is local to the
> > backend)?
> >
> > How about setting parallel_setup_cost to disable_cost in costsize.c for
> > your specific scan method.
>
> How can I do it if i just implementing my AM and not going to change any
> postgres code?
I think a set_rel_pathlist hook that prevents parallel paths from being
considered would be your best bet for now. But I encourage you to
suggest a patch to tableam to support it properly in future releases.
Greetings,
Andres Freund