Re: [geomesa-users] Geotools Join queries

[Emilio Lahr-Vivaz <elahrvivaz@xxxxxxxx>]

Hi Dave,

We don't support joins through the query like that - joins against a 
no-sql database tend to be very expensive. But we do have a few options. 
If available, probably the best approach is to use our spark support and 
do an in-memory join. If not, we also have a join WPS (web process 
service) that you can use, but it limits the features from the first set 
to 128: 
https://github.com/locationtech/geomesa/blob/master/geomesa-accumulo/geomesa-accumulo-datastore/src/main/scala/org/locationtech/geomesa/accumulo/process/JoinProcess.scala

If you want to use spark, I can try to find some examples for you.

Thanks,

Emilio


On 04/11/2017 06:05 PM, David Boyd wrote:
> I have a feeling this is not supported but I would ask.
>
> I have two featuretypes, with a common foreign_key between them.
> I want to join on that foreign_key and retrieve columns/properties from
> both featuretypes.
>
> I found an example of this in the geotools documentation, but I can't 
> get it to work.
> I simply can't find the name of the join column to retrieve.
>
> Below is my code:
>
> >         String propertynames[] = { 
> > "\"GDELTArtifactRecordset.SourceFileName\"","\"GDELTArtifactRecordset.GlobalEventID\"","b.EventCode\""};
> >         FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2();
> >         Filter jfilter = 
> > ff.equals(ff.property("GDELTArtifactREcordset.GlobalEventID"), 
> > ff.property("b.GlobalEventID"));
> >         Query query = new Query("GDELTArtifactRecordset");
> >         query.setPropertyNames(propertynames);
> >
> >         Join join = new Join("EventRecordset", jfilter);
> >         join.setAlias("b");
> >         query.getJoins().add(join);
> >
> > query.setFilter(ff.greaterOrEqual(ff.property("GDELTArtifactRecordset.GlobalEventID"), 
> > ff.literal(545650000)));
> >         query.setStartIndex(0);
> >         CachedRowSet rowset = 
> > searchPersistor.search(query).getResults();
> I have tried numerous various of the returned join column, but it will 
> no accept any column not in my GDELTArtifactRecordset.