To answer my own question:
The computed properties and the alias must be used together.
This is similar to addComputedPropertie(alias, expression).
Multiple aliases and multiple expressions must be seperated with TABS
(pretty difficult to do in a browser).
To use the SpatialExtent function, simply enter a name in the Alias
field, eg: extent,
then enter SpatialExtents("name of geometry column") in the computed
properties field.
Aggregates does not work with geometry columns, but does work with the
SpatialExtents function.
And the OGR provider, which I used, does not support the aggreate
instructions, and seems to ignore
any computed properties :(.
Regards, Kenneth Skovhede, GEOGRAF A/S
Kenneth Skovhede, GEOGRAF A/S skrev:
I'm having trouble understanding how the "Select Aggregates" system
works.
I expect it to be similar to the "GROUP BY" SQL command.
But, on the test page:
http://localhost/mapguide/mapagent/selectfeaturesform.html
I have the fields "Properties" and "Computed Properties".
If I enter nothing in the "Properties" field, or the name of a spatial
column, I get a "Type error".
If I enter the name of an existing column, I get all the rows
containing this column.
The "Computed Properties" field seems to accept anything, and has no
effect on the output.
I would like to calculate the actual extents of the geometry of the
entire featuresource.
There seems to exist an FDO command called "SpatialExtents", but I
don't see how I
can use that function from MapGuide.
Any help is appreciated!
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