On Thu, 2007-08-16 at 10:52 -0700, Michael Smedberg wrote: > I believe that Postgres has an optimization that “short-circuits” plan > execution when the SQL contains a LIMIT clause, but no “order by” or > other function that requires the whole result set. It seems like > PostGIS turns this optimization off (I’m using PostGIS 1.2.1.) Is > this a known bug? Is there a workaround that would allow me to have > poorly constrained GIS queries return quickly (if it’s poorly > constrained, I don’t care about the results, I just want to know that > there are too many to display)? In other words, is there a way for me > to KNOW it’s poorly constrained without having to wait for the whole > (large) result set to be generated?
(cut) > I’m a newbie to this list, so please forgive me if this is a dumb > question… No, it's actually a good question :) The first thing to notice is that your queries are different because your second query has a WHERE clause - does your first query behave any differently with a WHERE clause added? Make sure you choose a condition that selects a similar percentage of the table as a good test. HTH, Mark. -- ILande - Open Source Consultancy http://www.ilande.co.uk _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
