Re: Optimizer internals

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