datafu.pig.bags
Class FirstTupleFromBag

java.lang.Object
  org.apache.pig.EvalFunc<T>
      datafu.pig.util.SimpleEvalFunc<org.apache.pig.data.Tuple>
          datafu.pig.bags.FirstTupleFromBag

public class FirstTupleFromBag
extends SimpleEvalFunc<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)
 
 

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

FirstTupleFromBag()

Method Summary

org.apache.pig.data.Tuple	call(org.apache.pig.data.DataBag bag, org.apache.pig.data.Tuple defaultValue)
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 org.apache.pig.EvalFunc

finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getSchemaName, 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

FirstTupleFromBag

public FirstTupleFromBag()

Method Detail

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