org.apache.pig.piggybank.evaluation.math
Class DoubleDoubleBase

java.lang.Object
  org.apache.pig.EvalFunc<Double>
      org.apache.pig.piggybank.evaluation.math.Base
          org.apache.pig.piggybank.evaluation.math.DoubleDoubleBase

Direct Known Subclasses:

ATAN2, HYPOT, IEEEremainder, POW

public abstract class DoubleDoubleBase
extends Base

base class for math udfs that return Double value

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

DoubleDoubleBase()

Method Summary

Double	exec(Tuple input) java level API
List<FuncSpec>	getArgToFuncMapping() Allow a UDF to specify type specific implementations of itself.

Methods inherited from class org.apache.pig.piggybank.evaluation.math.Base

outputSchema

Methods inherited from class org.apache.pig.EvalFunc

finish, getCacheFiles, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, isAsynchronous, progress, setPigLogger, setReporter, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

DoubleDoubleBase

public DoubleDoubleBase()

Method Detail

exec

public Double exec(Tuple input)
            throws IOException

java level API

Specified by:

exec in class EvalFunc<Double>

Parameters:

input - expects a tuple with a single Double value

output - returns a Double value

Returns:

result, of type T.

Throws:

IOException

getArgToFuncMapping

public List<FuncSpec> getArgToFuncMapping()
                                   throws FrontendException

Description copied from class: EvalFunc

Allow a UDF to specify type specific implementations of itself. For example, an implementation of arithmetic sum might have int and float implementations, since integer arithmetic performs much better than floating point arithmetic. Pig's typechecker will call this method and using the returned list plus the schema of the function's input data, decide which implementation of the UDF to use.

Overrides:

getArgToFuncMapping in class EvalFunc<Double>

Returns:

A List containing FuncSpec objects representing the EvalFunc class which can handle the inputs corresponding to the schema in the objects. Each FuncSpec should be constructed with a schema that describes the input for that implementation. For example, the sum function above would return two elements in its list:

1. FuncSpec(this.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.DOUBLE)))
2. FuncSpec(IntSum.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.INTEGER)))

This would indicate that the main implementation is used for doubles, and the special implementation IntSum is used for ints.

Throws:

FrontendException