Automatic extent derivation

[Steve Hall]

Hi all,

I'm doing some R & D for a system that is going need to produce as many as 40 maps per second for a busy web site.  The mapdata is going come from either PostGIS or Oracle Spatial.  Each map will be different and should immediately zoom to the full extent "defined" by one of the layers which will be a spatial query "defining" the results of the users request.

My question is about the best way of deriving that extent.  I could (effectively) run the spatial query twice - once myself in PHP/MapScript (or whatever language is used to create the map) to get the extent (and hence set it "into" the MapServer request) and then MapServer itself will perform a very similar query to actually draw the map.  As performance is of paramount importance i'd like to remove this "duplication" if at all possible.

I may be missing something obvious but is there an easy way to do this?  Ideally i'd just like to specify that the map should always zoom to the extent "implied" by a particular layers features.

Many thanks for your thoughts,

Steve H
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