On Mon, Nov 01, 2010 at 04:18:30PM -0700, Ben wrote: > hello -- > > i am not a postgis user, but i am interested in range datatypes and gist > indexing. there are some extensions for postgresql which expose such types > (temporal, cube, etc.) but as far as i can tell all of them use the default > geometric operator selectivity functions, which are all stubs in mainline > postgresql and return hard-coded constants -- not ideal. > > i've been investigating postgis and it appears that you have real selectivity > functions for your operators. > > 1 - is this true? do they work well? which operators work? (&&, @>, etc)?
True. Work well. You can evaluate by using 'explain analyze <query>' which gives you estimated and actual number of rows. Only && is implemented custom (geometry_gist_sel) altought gathered stats might be helpful for implementing more. > 2 - is there any documentation describing how they work (besides the source > code)? i'm interested in the kind of statistics you use. You may find something in postgis-devel archives around early 2005. Me and Mark Cave involved. Code should have interesting comments too. > 3 - would it be possible for someone to backport the selectivity functions > to, say, temporal postgres or cube? would you recommend it? Sure, why not. --strk; () Free GIS & Flash consultant/developer /\ http://strk.keybit.net/services.html _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
