org.apache.pig.builtin

Class StringMin

java.lang.Object

org.apache.pig.EvalFunc<java.lang.String>

org.apache.pig.builtin.StringMin

All Implemented Interfaces:

Accumulator<java.lang.String>, Algebraic

public class StringMin
extends EvalFunc<java.lang.String>
implements Algebraic, Accumulator<java.lang.String>

This method should never be used directly, use MIN.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	StringMin.Final
static class	StringMin.Initial
static class	StringMin.Intermediate

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

EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
StringMin()

Method Summary

Methods

Modifier and Type	Method and Description
void	accumulate(Tuple b) Pass tuples to the UDF.
void	cleanup() Called after getValue() to prepare processing for next key.
java.lang.String	exec(Tuple input) This callback method must be implemented by all subclasses.
java.lang.String	getFinal() Get the final function.
java.lang.String	getInitial() Get the initial function.
java.lang.String	getIntermed() Get the intermediate function.
java.lang.String	getValue() Called when all tuples from current key have been passed to accumulate.
protected static java.lang.String	min(Tuple input)
Schema	outputSchema(Schema input) Report the schema of the output of this UDF.

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, 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

Constructor Detail

StringMin

public StringMin()

Method Detail

exec

public java.lang.String exec(Tuple input)
                      throws java.io.IOException

Description copied from class: EvalFunc

This callback method must be implemented by all subclasses. This is the method that will be invoked on every Tuple of a given dataset. Since the dataset may be divided up in a variety of ways the programmer should not make assumptions about state that is maintained between invocations of this method.

Specified by:

exec in class EvalFunc<java.lang.String>

Parameters:

input - the Tuple to be processed.

Returns:

result, of type T.

Throws:

java.io.IOException

getInitial

public java.lang.String getInitial()

Description copied from interface: Algebraic

Get the initial function.

Specified by:

getInitial in interface Algebraic

Returns:

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

getIntermed

public java.lang.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 java.lang.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.

min

protected static java.lang.String min(Tuple input)
                               throws ExecException

Throws:

ExecException

outputSchema

public Schema outputSchema(Schema input)

Description copied from class: EvalFunc

Report the schema of the output of this UDF. Pig will make use of this in error checking, optimization, and planning. The schema of input data to this UDF is provided.

The default implementation interprets the OutputSchema annotation, if one is present. Otherwise, it returns null (no known output schema).

Overrides:

outputSchema in class EvalFunc<java.lang.String>

Parameters:

input - Schema of the input

Returns:

Schema of the output

accumulate

public void accumulate(Tuple b)
                throws java.io.IOException

Description copied from interface: Accumulator

Pass tuples to the UDF.

Specified by:

accumulate in interface Accumulator<java.lang.String>

Parameters:

b - A tuple containing a single field, which is a bag. The bag will contain the set of tuples being passed to the UDF in this iteration.

Throws:

java.io.IOException

cleanup

public void cleanup()

Description copied from interface: Accumulator

Called after getValue() to prepare processing for next key.

Specified by:

cleanup in interface Accumulator<java.lang.String>

getValue

public java.lang.String getValue()

Description copied from interface: Accumulator

Called when all tuples from current key have been passed to accumulate.

Specified by:

getValue in interface Accumulator<java.lang.String>

Returns:

the value for the UDF for this key.