Re: Custom function in where clause - Mailing list pgsql-performance

From Pena Kupen
Subject Re: Custom function in where clause
Date
Msg-id 29875759.2181341912638615.JavaMail.kupen@wippies.fi
Whole thread Raw
In response to Custom function in where clause  (Pena Kupen <kupen@wippies.fi>)
List pgsql-performance
Hi and thank's guys!

First trying this Brendan's recommendation.

It seems only a small difference between sql and PL/pgSQL. from 40-->37. Not so good yet.
I will try Maxim's little later and you all know.

--
kupen

Brendan Jurd [direvus@gmail.com] kirjoitti:
> On 10 July 2012 18:36, Pena Kupen <kupen@wippies.fi> wrote:
> > Hi,
> >
> > I have searched solution to my problem a few days. On my query, there is big
> > performance problem.
> > It seems to me, that problem is on where-part of sql and it's function.
> >
>
> > How should I handle this situation and use function?
> >
>
> I would start by rewriting your function in plain SQL rather than
> PL/pgSQL.  As a general rule, don't write a function in PL/pgSQL
> unless you really need procedurality.  This function does not.
>
> For example:
>
> CREATE OR REPLACE FUNCTION get_level_value(_user integer, _id, _area)
> RETURNS integer
>    AS $$
>   -- Return 3 if there are matching records in table_o, otherwise return 1.
>   SELECT CASE WHEN EXISTS (
>          SELECT id
>          FROM table_o
>          WHERE userid=_user AND
>                id=_id AND
>                area=_area
>   ) THEN 3 ELSE 1 END;
> $$
> LANGUAGE sql STABLE;
>
> Cheers,
> BJ
>


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