org.apache.pig.impl.builtin
Class PoissonSampleLoader

java.lang.Object
  org.apache.pig.LoadFunc
      org.apache.pig.impl.builtin.SampleLoader
          org.apache.pig.impl.builtin.PoissonSampleLoader

public class PoissonSampleLoader
extends SampleLoader

See "Skewed Join sampler" in http://wiki.apache.org/pig/PigSampler

Field Summary

static String

NUMROWS_TUPLE_MARKER

Fields inherited from class org.apache.pig.impl.builtin.SampleLoader

loader, numSamples

Constructor Summary

PoissonSampleLoader(String funcSpec, String ns)

Method Summary

void	computeSamples(ArrayList<Pair<FileSpec,Boolean>> inputs, PigContext pc) Computes the number of samples for the loader
Tuple	getNext() Retrieves the next tuple to be processed.
void	prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader, PigSplit split) Initializes LoadFunc for reading data.

Methods inherited from class org.apache.pig.impl.builtin.SampleLoader

getInputFormat, getLoadCaster, getNumSamples, relativeToAbsolutePath, setLocation, setNumSamples, setUDFContextSignature, skipNext

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getPathStrings, join

Methods inherited from class java.lang.Object

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

Field Detail

NUMROWS_TUPLE_MARKER

public static final String NUMROWS_TUPLE_MARKER

See Also:

Constant Field Values

Constructor Detail

PoissonSampleLoader

public PoissonSampleLoader(String funcSpec,
                           String ns)

Method Detail

getNext

public Tuple getNext()
              throws IOException

Description copied from class: LoadFunc

Retrieves the next tuple to be processed. Implementations should NOT reuse tuple objects (or inner member objects) they return across calls and should return a different tuple object in each call.

Specified by:

getNext in class LoadFunc

Returns:

the next tuple to be processed or null if there are no more tuples to be processed.

Throws:

IOException - if there is an exception while retrieving the next tuple

computeSamples

public void computeSamples(ArrayList<Pair<FileSpec,Boolean>> inputs,
                           PigContext pc)
                    throws ExecException

Computes the number of samples for the loader

Overrides:

computeSamples in class SampleLoader

Parameters:

inputs - : Set to pig inputs

pc - : PigContext object

Throws:

ExecException

prepareToRead

public void prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader,
                          PigSplit split)
                   throws IOException

Description copied from class: LoadFunc

Initializes LoadFunc for reading data. This will be called during execution before any calls to getNext. The RecordReader needs to be passed here because it has been instantiated for a particular InputSplit.

Overrides:

prepareToRead in class SampleLoader

Parameters:

reader - RecordReader to be used by this instance of the LoadFunc

split - The input PigSplit to process

Throws:

IOException - if there is an exception during initialization