I am quite fond of the Transform extension (and the transform WPS process).
The DataStores do their best to be opaque in order to leverage any "native"
support provided by the database or web service or file format used.
So the good news is GeoMesa is free to optimise, but it only has access to
the fixed query data structure.
A few specific very specific transformations are documented, force CRS,
reproject and so on ... and the javadocs are hard to follow for
implementors.
The other avenue is the use of xpath expressions by the Query PropertyName
data structure. It is kind of up to each datastore for how much of that
they are willing to support.
I like the idea of combining transform and query, but it has not been done
yet. It may match WFS 2.0 better if we make use of XPath as indicated above.
Jody Garnett
On Sun, Apr 13, 2014 at 1:10 AM, Anthony F <[email protected]> wrote:
> In the Query api, I can specify a subset of columns that I would like
> returned as part of my query. It would be useful if I could pass in a list
> of transform definitions or expressions and have the underlying database
> execute the transformations. This would be similar to a SQL projection
> such as
>
> 'select concat('id', 'name') as newname, buffer(the_geom, 0.1) as bufgeom
> from mygeomtable where within(the_geom, polygonWKT)'
>
> Is there a simple way to do this sort of thing that I have overlooked?
> I've been digging around in the Query api and the Transform process code to
> see if this is possible. I need a way to send the list of transform
> definitions to the underlying DataStore (in this case GeoMesa) so that it
> can execute the transformation in an optimal way. In the GeoMesa case, we
> would be able to leverage distributed parallel processing to compute an
> computationally expensive transformation.
>
> If there isn't a simple way, is there a workaround that is recommended?
>
> Thanks,
> Anthony
>
>
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