Hi,

In QGIS there is something what we call 'Geometry-generators': you actually 
generate a geometry based on some other geometry and some parameters, coming 
from 'expressions'.

In this way it is for example possible to create some kind of polygon based on 
a point layer.
My goal: create rotated 'wedges/sectors' with a data-based rotation from a 
point layer (talking about GSM 'beams' here), but (tricky part): size depending 
on the current map scale...

My plan to mimic this in a Geoserver WMS:
- have a point layer in postgis
- create a postgis function to create a wedge (taking the attribute in account)
- create a SQL view layer which creates a geom by calling this function 

Question: is it possible for geoserver to 'insert' the scale (as being 
requested in the WMS request) into this function-call as parameter. Something 
like $SCALE or $SCALE_DENOMINATOR or so, which is to be replaced by Geoserver 
BEFORE handling over the query to postgis?

Looking into the docs[0], it looks like it would be possible with a (client 
site added) parameter. But in this case the 'scale'-information should come 
from the WMS-request-info (as it is not possible to change the client apps for 
us).

Mmm, now I am afraid this is maybe hard as it makes it impossible to 'cache' 
this view...

Anyone idea's?

Regards,

Richard Duivenvoorde


[0] https://docs.geoserver.org/stable/en/user/data/database/sqlview.html





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