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Re: Optimizer internals

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: John Vincent <pgsql-performance(at)lusis(dot)org>
Cc: PGSQL Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Optimizer internals
Date: 2006-06-15 22:23:45
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Thu, Jun 15, 2006 at 03:43:09PM -0400, John Vincent wrote:
> >Any suggestions? FYI the original question wasn't meant as a poke at
> >comparing PG to MySQL to DB2. I'm not making an yvalue judgements either
> >way. I'm just trying to understand how we can use it the best way possible.
> >
> >If anyone from the bizgres team is watching, have they done any work in
> >this area?
> >
> >Thanks.
> >John
> >
> Actually we just thought about something. With PG, we can create an index
> that is a SUM of the column where indexing, no? We're going to test this in
> a few hours. Would that be able to be satisfied by an index scan?
> Also, we're looking at the link provided for the materialized views in PG.
> Thanks.

decibel=# create index test on i ( sum(i) );
ERROR:  cannot use aggregate function in index expression

BTW, there have been a number of proposals to negate the effect of not
having visibility info in indexes. Unfortunately, none of them have come
to fruition yet, mostly because it's a very difficult problem to solve.
But it is something that the community would like to see happen.
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software    work: 512-231-6117
vcard:       cell: 512-569-9461

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