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

Class GenericUDAFFirstValue

java.lang.Object

org.apache.hadoop.hive.ql.udf.generic.AbstractGenericUDAFResolver

org.apache.hadoop.hive.ql.udf.generic.GenericUDAFFirstValue

All Implemented Interfaces:

GenericUDAFResolver, GenericUDAFResolver2

@WindowFunctionDescription(description=,
                           supportsWindow=true,
                           pivotResult=false,
                           impliesOrder=true)
public class GenericUDAFFirstValue
extends AbstractGenericUDAFResolver

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GenericUDAFFirstValue.GenericUDAFFirstValueEvaluator

Constructor Summary

Constructors

Constructor and Description
GenericUDAFFirstValue()

Method Summary

Methods

Modifier and Type	Method and Description
protected GenericUDAFFirstValue.GenericUDAFFirstValueEvaluator	createEvaluator()
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

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

Constructor Detail

GenericUDAFFirstValue

public GenericUDAFFirstValue()

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

createEvaluator

protected GenericUDAFFirstValue.GenericUDAFFirstValueEvaluator createEvaluator()