From: =?iso-8859-1?q?C=E9dric_Villemain?= <cedric.villemain@dalibo.com>
Organization: dalibo.com
To: Martin Kjeldsen <martin@martinkjeldsen.dk>
Subject: Re: Bad prepare performance
Date: Tue, 1 Apr 2008 09:53:36 +0200
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Hi Martin, please CC the mailing-list,=20
then others can repply ;)

C=E9dric Villemain (13:59 2008-03-31):
> Le Monday 31 March 2008, Martin Kjeldsen a =E9crit=A0:
> > I've done the same query on a 8.2.5 database. The first one is prepared
> > first and the other is executed directly.
> >
> > I understand why the there is such a great difference between the two w=
ays
> > of executing the query (postgres has no way of knowing that $1 will be
> > quite big and that the result is not too big).
> >
> > I could just avoid using prepare statements, but this is done=20
automatically
> > with Perl's DBD::Pg. I know how to avoid using prepare statements (avoid
> > having placeholders in the statement), but that is not the prettiest of
> > work arounds.=20
>=20
> Did you saw this option :
>=20
>   $sth =3D $dbh->prepare("SELECT id FROM mytable WHERE val =3D ?",
>                        { pg_server_prepare =3D> 0 });
>=20
> Then, *this* query will not be prepared by the server.

This works very well. Thanks!

Still I regard this as a work around and the optimal solution would be to=20
allow the prepare statement to be prepared with an max(guid) is close to $1=
=20
hint or something like that.=20

I heard something about delayed prepare, where the prepared statements is=20
prepared on first use, this would solve my problem. Is this something being=
=20
work on right now?

Best regards


Martin Kjeldsen

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