Is this not similar to the aggregate process already implemented <https://docs.geoserver.org/latest/en/user/services/wps/processes/gs.html>? You may be able to get a similar result by allowing aggregationAttribute to have multiple values. -- Jody Garnett
On Tue, 29 Sep 2020 at 02:21, Marco Volpini <[email protected]> wrote: > Dear all, > I'm writing to propose the creation of a new vector rendering > transformation and have your feedback about it. The following listing shows > how it would appear: > > <Transformation> > <ogc:Function name="vec:GroupingRenderingTransformation"> > <ogc:Function name="parameter"> > <ogc:Literal>data</ogc:Literal> > </ogc:Function> > <ogc:Function name="parameter"> > <ogc:Literal>groupByAttributes</ogc:Literal> > <ogc:Literal>attribute1</ogc:Literal> > <ogc:Literal>attribute2</ogc:Literal> > .... > <ogc:Literal>attributeN</ogc:Literal> > </<ogc:Function name="parameter"> > <ogc:Function name="parameter"> > <ogc:Literal>aggregator</ogc:Literal> > <ogc:Literal>min</ogc:Literal> > </ogc:Function> > <ogc:Function name="parameter"> > <ogc:Literal>aggregationAttribute</ogc:Literal> > <ogc:Literal>attributeName</ogc:Literal> > </ogc:Function> > </ogc:Function> > </Transformation> > > > - the groupByAttributes parameter allows to define the feature's > attributes to produce the groups on which do aggregation; > - the aggregator parameter specifies the aggregation to perform (eg. > min/max); > - the aggregationAttribute provides the feature attribute used for the > aggregation. > > For instance, in case of a min aggregation, the rendering transformation > will allow to return only the feature, for each group, having the minimum > value for the aggregationAttribute. > > Moreover, in order to give a consistent result, the rendering > transformation will need to be fed with sorted features. > This would allow to overcome issues that would arise if sorting is handled > inside the RT: > > - FeatureCollection sort method accepts only one SortBy object, while > the RT would allow to define more grouping attributes. > - The FeatureCollection sort method doesn't support ComplexFeatures. > > In case the RT is issued through a sld, the sortBy attributes can be > defined through the vendorOption, while in case of a WPS process, they can > be provided through the Query object. > > The output of the rendering transformation will be a FeatureCollection > wrapper, and the necessary computation will be performed in the hasNext > method of the corresponding FeatureIterator. > > Best regards, > > Marco Volpini > > > _______________________________________________ > Geoserver-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/geoserver-devel >
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