Hi, Mixed grid queries are frequent, at least on something like yr.
Assuming it does work with a single table, I guess the only way to really find out whether it works well is to try it. :-) Regards, Michael A. ----- Original Message ----- > On Thu, Jul 07, 2011 at 11:06:34PM +0000, Michael Akinde wrote: > > > Due to the number of grids I am somewhat leery of setting up (and > > tearing down) multiple tables on an operational database (data grids > > change over time). Keeping it in one table would presumably be > > better, assuming it is practicable. > > It is practicable to keep everything in one table, but if you never > get items from mixed grids in the same spatial query you may give > the optimizer better informations by keeping those grids in separate > tables. For instance, querying for all items in a given bounding box > might return X items from the lowest-resolution grid, X*2 from the > next higher resolution, X*4 for the next and so on.... the estimator > would think it's so many rows that an index scan is not worth the cost > while indeed you may be just querying the lowest-resolution one. > > But it's just a guess, only you know the kind of queries you're going > to run and how the planner deals with them. > > --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 _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
