Re: Speeding up Aggregates

On Fri, 2003-10-03 at 17:53, Dror Matalon wrote:
> On Fri, Oct 03, 2003 at 05:44:49PM -0400, Rod Taylor wrote:
> > > item_max_date() looks like this:
> > > select max(dtstamp) from items where channel = $1 and link = $2;
> >
> > It is too bad the (channel, link) index doesn't have dtstamp at the end
> > of it, otherwise the below query would be a gain (might be a small one
> > anyway).
> >
> > select dtstamp
> > from items
> > where channel = $1
> > and link = $2
> > ORDER BY dtstamp DESC
> > LIMIT 1;

It didn't make a difference even with the 3 term index? I guess you
don't have very many common values for channel / link combination.

How about the below? Note the word STABLE on the end.

CREATE or REPLACE FUNCTION item_max_date (int4, varchar) RETURNS
timestamptz AS '
select max(dtstamp) from items where channel = $1 and link = $2;
' LANGUAGE 'sql' STABLE;