Re: Optimizer internals - Mailing list pgsql-performance

From Jim C. Nasby
Subject Re: Optimizer internals
Date
Msg-id 20060615222344.GB93655@pervasive.com
Whole thread Raw
In response to Re: Optimizer internals  ("John Vincent" <pgsql-performance@lusis.org>)
Responses Re: Optimizer internals
List 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
decibel=#

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@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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