Compile Error with custom Test UDAF from cubert code

[swapnils10]

I have a scenario in which i need to pick the first non null element for each grouping key of CUBE operator.

Where can i find reference steps to write a custom aggregation function for CUBE operator in CUBERT.

The reference for it at link http://linkedin.github.io/Cubert/userdefined/aggregations.html is empty.

Also, I tried to implement custom test UDAF as specified in below path :

https://github.com/linkedin/Cubert/blob/master/src/test/java/com/linkedin/cubert/operator/TestUDAF.java

I have created the jar, registered that jar and declared the function in cubert script which uses that UDAF. However, the script fails with below error :

Caused by: PreconditionException [MISC_ERROR] com.comscore.cookiecount.cubert.functions.TestUDAF should implement one of these interfaces: AdditiveCubeAggregate, PartitionedAdditiveAggregate, EasyCubeAggregate
at com.linkedin.cubert.operator.CubeOperator.createAggregators(CubeOperator.java:641)
at com.linkedin.cubert.operator.CubeOperator.createOutputSchema(CubeOperator.java:449)
at com.linkedin.cubert.operator.CubeOperator.getPostCondition(CubeOperator.java:413)
at com.linkedin.cubert.analyzer.physical.SemanticAnalyzer.getPostCondition(SemanticAnalyzer.java:811)
at com.linkedin.cubert.analyzer.physical.SemanticAnalyzer.visitOperator(SemanticAnalyzer.java:309)
... 9 more

Caused by: PreconditionException [MISC_ERROR] com.myudfs.cubert.functions.
TestUDAF should implement one of these interfaces: AdditiveCubeAggregate, PartitionedAdditiveAggregate, EasyCubeAggregate
at com.linkedin.cubert.operator.CubeOperator.createAggregators(CubeOperator.java:641)
at com.linkedin.cubert.operator.CubeOperator.createOutputSchema(CubeOperator.java:449)
at com.linkedin.cubert.operator.CubeOperator.getPostCondition(CubeOperator.java:413)
at com.linkedin.cubert.analyzer.physical.SemanticAnalyzer.getPostCondition(SemanticAnalyzer.java:811)
at com.linkedin.cubert.analyzer.physical.SemanticAnalyzer.visitOperator(SemanticAnalyzer.java:309)
... 9 more

Is there something I'm missing in this implementation ?

Thanks,

Swapnil Salunkhe