datafu.pig.bags

Class TupleFromBag

java.lang.Object

org.apache.pig.EvalFunc<T>

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

datafu.pig.bags.TupleFromBag

All Implemented Interfaces:

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

public class TupleFromBag
extends org.apache.pig.AccumulatorEvalFunc<org.apache.pig.data.Tuple>

This UDF will extract a tuple from a bag based on a specified index.

There are three input parameter:

1. DataBag
2. Index
3. Default tuple (Optional)

Example:

 
 define TupleFromBag datafu.pig.bags.TupleFromBag();
 %declare defaultTuple TOTUPLE(0,'NO_NUMBER')

 data = LOAD 'input' using PigStorage(',') AS (a:INT,b:CHARARRAY);
 -- input:
 (1,a)
 (1,b)
 (1,c)
 (2,d)
 (2,e)
 (2,f)
 (3,g)
 (3,h)
 (3,i)

 grouped = GROUP data BY a;

 --output:
 {group: int,data: {(a: int,b: chararray)}}
 (1,{(1,c),(1,b),(1,a)})
 (2,{(2,f),(2,e),(2,d)})
 (3,{(3,i),(3,h),(3,g)})

 result1 = FOREACH grouped GENERATE
           group AS a,
           TupleFromBag(data, 0);

 --output:
 {a: int,(a: int,b: chararray)}
 (1,(1,c))
 (2,(2,f))
 (3,(3,i))


 result2 = FOREACH grouped GENERATE
           group AS a,
           TupleFromBag(data,0).b as first_b,
           TupleFromBag(data,1).b as second_b;

 --output:
 {a: int,first_b: chararray,second_b: chararray}
 (1,c,b)
 (2,f,e)
 (3,i,h)


 result3 = FOREACH grouped GENERATE
           group AS a,
           TupleFromBag(data,0).b as first_b,
           TupleFromBag(data,3).b as forth_b;
 
 --output:
 {a: int,first_b: chararray,forth_b: chararray}
 (1,c,)
 (2,f,)
 (3,i,)

 result4 = FOREACH grouped GENERATE
           group AS a,
           TupleFromBag(data,0,$emptyTuple).b as first_b,
           TupleFromBag(data,3,$emptyTuple).b as forth_b;
 
 --output:
 {a: int,first_b: chararray,forth_b: chararray}
 (1,c,NO_NUMBER)
 (2,f,NO_NUMBER)
 (3,i,NO_NUMBER)
  
 

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
TupleFromBag()

Method Summary

Modifier and Type	Method and Description
void	accumulate(org.apache.pig.data.Tuple tinput)
void	cleanup()
org.apache.pig.data.Tuple	getValue()
org.apache.pig.impl.logicalLayer.schema.Schema	outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input)

Methods inherited from class org.apache.pig.AccumulatorEvalFunc

exec

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

TupleFromBag

public TupleFromBag()

Method Detail

accumulate

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

Specified by:

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

Specified by:

accumulate in class org.apache.pig.AccumulatorEvalFunc<org.apache.pig.data.Tuple>

Throws:

java.io.IOException

outputSchema

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

Overrides:

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

cleanup

public void cleanup()

Specified by:

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

Specified by:

cleanup in class org.apache.pig.AccumulatorEvalFunc<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>

Specified by:

getValue in class org.apache.pig.AccumulatorEvalFunc<org.apache.pig.data.Tuple>