[postgis-users] PostGIS Raster for Met Data

[Michael Akinde]

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
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