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;
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