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

java.lang.Object
  org.apache.hadoop.hive.ql.udf.generic.GenericUDAFCount

All Implemented Interfaces:

GenericUDAFResolver, GenericUDAFResolver2

public class GenericUDAFCount
extends Object
implements GenericUDAFResolver2

This class implements the COUNT aggregation function as in SQL.

Nested Class Summary

static class

GenericUDAFCount.GenericUDAFCountEvaluator GenericUDAFCountEvaluator.

Constructor Summary

GenericUDAFCount()

Method Summary

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

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericUDAFCount

public GenericUDAFCount()

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

Parameters:

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

Throws:

SemanticException

getEvaluator

public GenericUDAFEvaluator getEvaluator(GenericUDAFParameterInfo paramInfo)
                                  throws SemanticException

Description copied from interface: GenericUDAFResolver2

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 GenericUDAFResolver2

Parameters:

paramInfo - The parameter information that is applicable to the UDAF being invoked.

Throws:

SemanticException