Обсуждение: Hinting the planner

Hello all.

I have some tables that contain exactly 1 row and that I use for searches with
JOIN.

Does it make any sense to hint the planner about this?
If so, how can I send such hints to it?

--
Reg me, please!

Reg Me Please wrote:
> Hello all.
>
> I have some tables that contain exactly 1 row and that I use for searches with
> JOIN.
>
> Does it make any sense to hint the planner about this?
> If so, how can I send such hints to it?
>

You don't give hints to the planner.

The planner does use statistics gathered from an ANALYZE to generate the
best plan, so if you haven't analyzed your db you will not likely get
the best plans.

see
http://www.postgresql.org/docs/8.2/interactive/sql-analyze.html

and
http://www.postgresql.org/docs/8.2/interactive/sql-vacuum.html

also
http://www.postgresql.org/docs/8.2/interactive/maintenance.html

can explain these tasks in more detail.

If this is insufficient then you can also look at your config file.



--

Shane Ambler
pgSQL (at) Sheeky (dot) Biz

Get Sheeky @ http://Sheeky.Biz

Not the planner but you can hint the query as in this example
select /*+ ordered use_hash(code1)*/ * from table_1;

Martin
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> Date: Wed, 2 Jan 2008 00:15:14 +1030
> From: pgsql@Sheeky.Biz
> To: regmeplease@gmail.com
> CC: pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Hinting the planner
>
> Reg Me Please wrote:
> > Hello all.
> >
> > I have some tables that contain exactly 1 row and that I use for searches with
> > JOIN.
> >
> > Does it make any sense to hint the planner about this?
> > If so, how can I send such hints to it?
> >
>
> You don't give hints to the planner.
>
> The planner does use statistics gathered from an ANALYZE to generate the
> best plan, so if you haven't analyzed your db you will not likely get
> the best plans.
>
> see
> http://www.postgresql.org/docs/8.2/interactive/sql-analyze.html
>
> and
> http://www.postgresql.org/docs/8.2/interactive/sql-vacuum.html
>
> also
> http://www.postgresql.org/docs/8.2/interactive/maintenance.html
>
> can explain these tasks in more detail.
>
> If this is insufficient then you can also look at your config file.
>
>
>
> --
>
> Shane Ambler
> pgSQL (at) Sheeky (dot) Biz
>
> Get Sheeky @ http://Sheeky.Biz
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Have you searched our list archives?
>
> http://archives.postgresql.org/

---

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On Jan 1, 2008 10:27 AM, Martin Gainty <mgainty@hotmail.com> wrote:
>
>  Not the planner but you can hint the query as in this example
>  select /*+ ordered use_hash(code1)*/ * from table_1;

no, that's an oraclism.

mgainty@hotmail.com (Martin Gainty) writes:
> Not the planner but you can hint the query as in this example
> select /*+ ordered use_hash(code1)*/ * from table_1;

That might have some effect with Oracle; is there some reason why you
think this would be expected to have any effect on a PostgreSQL query?
--
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