org.apache.pig.builtin
Class SUM

java.lang.Object
  org.apache.pig.EvalFunc<T>
      org.apache.pig.builtin.AlgebraicByteArrayMathBase
          org.apache.pig.builtin.SUM

All Implemented Interfaces:

Accumulator<Double>, Algebraic

public class SUM
extends AlgebraicByteArrayMathBase

Generates the sum of a set of values. This class implements Algebraic, so if possible the execution will performed in a distributed fashion.

SUM can operate on any numeric type. It can also operate on bytearrays, which it will cast to doubles. It expects a bag of tuples of one record each. If Pig knows from the schema that this function will be passed a bag of integers or longs, it will use a specially adapted version of SUM that uses integer arithmetic for summing the data. The return type of SUM is double for float, double, or bytearray arguments and long for int or long arguments.

SUM implements the Accumulator interface as well. While this will never be the preferred method of usage it is available in case the combiner can not be used for a given calculation.

Nested Class Summary

protected static class	AlgebraicMathBase.KNOWN_OP
protected static interface	AlgebraicMathBase.KnownOpProvider
static class	SUM.Final
static class	SUM.Intermediate

Nested classes/interfaces inherited from class org.apache.pig.builtin.AlgebraicByteArrayMathBase

AlgebraicByteArrayMathBase.Initial

Nested classes/interfaces inherited from class org.apache.pig.EvalFunc

EvalFunc.SchemaType

Field Summary

protected AlgebraicMathBase.KnownOpProvider

opProvider

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

SUM()

Method Summary

List<FuncSpec>	getArgToFuncMapping() Allow a UDF to specify type specific implementations of itself.
String	getFinal() Get the final function.
String	getIntermed() Get the intermediate function.
protected void	setOp(AlgebraicMathBase.KNOWN_OP op)

Methods inherited from class org.apache.pig.builtin.AlgebraicByteArrayMathBase

accumulate, cleanup, doTupleWork, exec, getInitial, getSeed, getValue, outputSchema

Methods inherited from class org.apache.pig.EvalFunc

finish, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, isAsynchronous, progress, setInputSchema, setPigLogger, setReporter, setUDFContextSignature, warn

Methods inherited from class java.lang.Object

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

Field Detail

opProvider

protected AlgebraicMathBase.KnownOpProvider opProvider

Constructor Detail

SUM

public SUM()

Method Detail

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

setOp

protected void setOp(AlgebraicMathBase.KNOWN_OP op)

getIntermed

public String getIntermed()

Description copied from interface: Algebraic

Get the intermediate function.

Specified by:

getIntermed in interface Algebraic

Returns:

A function name of f_intermed. f_intermed should be an eval func. The return type of f_intermed.exec() has to be Tuple

getFinal

public String getFinal()

Description copied from interface: Algebraic

Get the final function.

Specified by:

getFinal in interface Algebraic

Returns:

A function name of f_final. f_final should be an eval func parametrized by the same datum as the eval func implementing this interface.