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.
getEvaluatorClass
Class<? extends UDAFEvaluator> getEvaluatorClass(List<TypeInfo> argClasses)
throws AmbiguousMethodException
- Gets the evaluator class corresponding to the passed parameter list.
- Throws:
AmbiguousMethodException
Copyright © 2009 The Apache Software Foundation