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

Class GenericUDAFnGrams

java.lang.Object

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

All Implemented Interfaces:

GenericUDAFResolver

public class GenericUDAFnGrams
extends Object
implements GenericUDAFResolver

Estimates the top-k n-grams in arbitrary sequential data using a heuristic.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GenericUDAFnGrams.GenericUDAFnGramEvaluator A constant-space heuristic to estimate the top-k n-grams.

Constructor Summary

Constructors

Constructor and Description
GenericUDAFnGrams()

Method Summary

Modifier and Type	Method and Description
GenericUDAFEvaluator	getEvaluator(TypeInfo[] parameters) Get the evaluator for the parameter types.

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericUDAFnGrams

public GenericUDAFnGrams()

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