[postgis-users] Mapserver extent question

[Bill Binko]

> > Hello,
> > 
> > I have an extent from mapserver (e.g., "-121.682485 38.408966
> > -121.231440 38.763359") that I want to feed back into a PostGIS query.
> > 
> > How do I express this extent in my query?
> > 
> > I want to write a query something like
> > 
> > select recid from tbl_points
> > where the_geom && <what goes here?> ;
> > 
> > 

Perhaps a simpler answer for you might be an undocumented feature in the 
Mapserver PostGIS interface.

If what you want is to be able to include the _current_ visible extent, 
you can use a special syntax like this: !BOX!

Months ago, I was playing with this.  I wanted to take the average value 
for the visible region and colorize the results based on the deviation 
from the average.  (I was just playing)  To do that, I needed the box so 
that I could calculate the average.  Of course, it's incredibly 
inefficient to do it this way, but here's how I used !BOX!...

DATA "parcel_shape from (select  parcel_shape, parcels.oid, 
      total_acreage/ave_acreage as pct, total_acreage, ave_acreage 
      from parcels join parcel_info on sdf_num = feat_num , 

      (select avg(total_acreage) as ave_acreage from parcels join 
      parcel_info on sdf_num = feat_num  WHERE (zoning like 'R%' OR 
      zoning is null) AND  parcel_shape && setSRID(!BOX!, 26759) and 
      Within(parcel_shape, setSRID(!BOX!, 26759))) as bar 

      where zoning like 'R%' or zoning is null) as foo using SRID=26759"

The point is that it will insert the current extents into the query string 
wherever you put !BOX!  (During 4.6 development, I submitted a patch that 
allows > 1 !BOX!.  Before that, you can only use it once.)

Hope this helps
Bill