org.apache.hadoop.hive.ql.udf.generic
Class GenericUDAFVariance

java.lang.Object
  org.apache.hadoop.hive.ql.udf.generic.AbstractGenericUDAFResolver
      org.apache.hadoop.hive.ql.udf.generic.GenericUDAFVariance

All Implemented Interfaces:

GenericUDAFResolver, GenericUDAFResolver2

Direct Known Subclasses:

GenericUDAFStd, GenericUDAFStdSample, GenericUDAFVarianceSample

public class GenericUDAFVariance
extends AbstractGenericUDAFResolver

Compute the variance. This class is extended by: GenericUDAFVarianceSample GenericUDAFStd GenericUDAFStdSample

Nested Class Summary

static class

GenericUDAFVariance.GenericUDAFVarianceEvaluator Evaluate the variance using the algorithm described by Chan, Golub, and LeVeque in "Algorithms for computing the sample variance: analysis and recommendations" The American Statistician, 37 (1983) pp.

Constructor Summary

GenericUDAFVariance()

Method Summary

GenericUDAFEvaluator

getEvaluator(TypeInfo[] parameters) Get the evaluator for the parameter types.

Methods inherited from class org.apache.hadoop.hive.ql.udf.generic.AbstractGenericUDAFResolver

getEvaluator

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GenericUDAFVariance

public GenericUDAFVariance()

Method Detail

getEvaluator

public GenericUDAFEvaluator getEvaluator(TypeInfo[] parameters)
                                  throws SemanticException

Description copied from interface: GenericUDAFResolver

Get the evaluator for the parameter types. The reason that this function returns an object instead of a class is because it is possible that the object needs some configuration (that can be serialized). In that case the class of the object has to implement the Serializable interface. At execution time, we will deserialize the object from the plan and use it to evaluate the aggregations.

If the class of the object does not implement Serializable, then we will create a new instance of the class at execution time.

Specified by:

getEvaluator in interface GenericUDAFResolver

Overrides:

getEvaluator in class AbstractGenericUDAFResolver

Parameters:

parameters - The types of the parameters. We need the type information to know which evaluator class to use.

Throws:

SemanticException