datafu.pig.bags

Class FirstTupleFromBag

java.lang.Object

org.apache.pig.EvalFunc<T>

datafu.pig.util.ContextualEvalFunc<T>

datafu.pig.util.SimpleEvalFunc<org.apache.pig.data.Tuple>

datafu.pig.bags.FirstTupleFromBag

All Implemented Interfaces:

org.apache.pig.Accumulator<org.apache.pig.data.Tuple>

public class FirstTupleFromBag
extends SimpleEvalFunc<org.apache.pig.data.Tuple>
implements org.apache.pig.Accumulator<org.apache.pig.data.Tuple>

Returns the first tuple from a bag. Requires a second parameter that will be returned if the bag is empty. Example:

 define FirstTupleFromBag datafu.pig.bags.FirstTupleFromBag();

 -- input:
 -- ({(a,1)})
 input = LOAD 'input' AS (B: bag {T: tuple(alpha:CHARARRAY, numeric:INT)});

 output = FOREACH input GENERATE FirstTupleFromBag(B, null);

 -- output:
 -- (a,1)
 
 

Nested Class Summary

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

org.apache.pig.EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
FirstTupleFromBag()

Method Summary

Methods

Modifier and Type	Method and Description
void	accumulate(org.apache.pig.data.Tuple tuple)
org.apache.pig.data.Tuple	call(org.apache.pig.data.DataBag bag, org.apache.pig.data.Tuple defaultValue)
void	cleanup()
org.apache.pig.data.Tuple	getValue()
org.apache.pig.impl.logicalLayer.schema.Schema	outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input) Override outputSchema so we can verify the input schema at pig compile time, instead of runtime

Methods inherited from class datafu.pig.util.SimpleEvalFunc

exec, getReturnType

Methods inherited from class datafu.pig.util.ContextualEvalFunc

getContextProperties, getInstanceName, getInstanceProperties, onReady, setUDFContextSignature

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, progress, setInputSchema, setPigLogger, setReporter, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

FirstTupleFromBag

public FirstTupleFromBag()

Method Detail

accumulate

public void accumulate(org.apache.pig.data.Tuple tuple)
                throws java.io.IOException

Specified by:

accumulate in interface org.apache.pig.Accumulator<org.apache.pig.data.Tuple>

Throws:

java.io.IOException

cleanup

public void cleanup()

Specified by:

cleanup in interface org.apache.pig.Accumulator<org.apache.pig.data.Tuple>

getValue

public org.apache.pig.data.Tuple getValue()

Specified by:

getValue in interface org.apache.pig.Accumulator<org.apache.pig.data.Tuple>

call

public org.apache.pig.data.Tuple call(org.apache.pig.data.DataBag bag,
                             org.apache.pig.data.Tuple defaultValue)
                               throws java.io.IOException

Throws:

java.io.IOException

outputSchema

public org.apache.pig.impl.logicalLayer.schema.Schema outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input)

Description copied from class: SimpleEvalFunc

Override outputSchema so we can verify the input schema at pig compile time, instead of runtime

Overrides:

outputSchema in class SimpleEvalFunc<org.apache.pig.data.Tuple>

Parameters:

input - input schema

Returns:

call to super.outputSchema in case schema was defined elsewhere