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Re: [geomesa-users] Geotools Join queries 
Emilio:

   Thanks.   That is what I thought.   Yeah, such joins are very expensive.

The plan was to eventually go to spark,  but I don't think
we have the schedule time.   Well, brute force and ignorance to the rescue.


On 4/11/17 10:15 PM, Emilio Lahr-Vivaz wrote:

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. 




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