org.apache.hadoop.hive.ql.exec

Interface UDAFEvaluatorResolver

All Known Implementing Classes:

DefaultUDAFEvaluatorResolver, NumericUDAFEvaluatorResolver

public interface UDAFEvaluatorResolver

The UDF Method resolver interface. A user can plugin a resolver to their UDF by implementing the functions in this interface. Note that the resolver is stored in the UDF class as an instance variable. We did not use a static variable because many resolvers maintain the class of the enclosing UDF as state and are called from a base class e.g. UDFBaseCompare. This makes it very easy to write UDFs that want to do resolution similar to the comparison operators. Such UDFs just need to extend UDFBaseCompare and do not have to care about the UDFMethodResolver interface. Same is true for UDFs that want to do resolution similar to that done by the numeric operators. Such UDFs simply have to extend UDFBaseNumericOp class. For the default resolution the UDF implementation simply needs to extend the UDF class.

Method Summary

Modifier and Type	Method and Description
java.lang.Class<? extends UDAFEvaluator>	getEvaluatorClass(java.util.List<TypeInfo> argClasses) Gets the evaluator class corresponding to the passed parameter list.

Method Detail

getEvaluatorClass

java.lang.Class<? extends UDAFEvaluator> getEvaluatorClass(java.util.List<TypeInfo> argClasses)
                                                    throws UDFArgumentException

Gets the evaluator class corresponding to the passed parameter list.

Throws:

UDFArgumentException