From: "Gaetano Mendola" <mendola@bigfoot.com>
Subject: Re: Performance inside and outside view ( WAS Re: Select the max on a
	field )
Date: Thu, 12 Sep 2002 17:53:38 +0200
Organization: Hub.Org Networking Services (http://www.hub.org)
Lines: 36
Message-ID: <alqd9s$mlb$1@news.hub.org>
References: <7350.1031842223@sss.pgh.pa.us>
To: pgsql-sql@postgresql.org


"Tom Lane" <tgl@sss.pgh.pa.us> wrote in message
news:7350.1031842223@sss.pgh.pa.us...
> "Gaetano Mendola" <mendola@bigfoot.com> writes:
> > Yes that's right it's help me,
> > but here the optimizer have some problems:
>
> What's the datatype of id_user, and why are you quoting the compared
> constant in some cases but not others?  I don't think the difference
> has anything to do with the view here ...

id_user is an INTEGER type.

Well what about this two selects:

a) SELECT DISTINCT ON (id_user) *
    FROM user_logs
   WHERE id_user = 5430
   ORDER BY id_user, id_user_log DESC;

b) CREATE VIEW last_user_logs AS
     SELECT DISTINCT ON (id_user) *
     FROM user_logs
     ORDER BY id_user, id_user_log DESC;

     SELECT *
     FROM last_user_logs
     WHERE id_user = 5430


I think that in the second case the filter is not pushed inside the view.

Ciao
Gaetano