org.apache.pig.piggybank.storage
Class SequenceFileLoader

java.lang.Object
  org.apache.pig.LoadFunc
      org.apache.pig.FileInputLoadFunc
          org.apache.pig.piggybank.storage.SequenceFileLoader

All Implemented Interfaces:

OrderedLoadFunc

public class SequenceFileLoader
extends FileInputLoadFunc

A Loader for Hadoop-Standard SequenceFiles. able to work with the following types as keys or values: Text, IntWritable, LongWritable, FloatWritable, DoubleWritable, BooleanWritable, ByteWritable

Field Summary

protected byte	keyType
protected static org.apache.commons.logging.Log	LOG
protected TupleFactory	mTupleFactory
protected org.apache.hadoop.io.serializer.SerializationFactory	serializationFactory
protected byte	valType

Constructor Summary

SequenceFileLoader()

Method Summary

org.apache.hadoop.mapreduce.InputFormat	getInputFormat() This will be called during planning on the front end.
Tuple	getNext() Retrieves the next tuple to be processed.
protected byte	inferPigDataType(Type t)
void	prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader, PigSplit split) Initializes LoadFunc for reading data.
protected void	setKeyType(Class<?> keyClass)
void	setLocation(String location, org.apache.hadoop.mapreduce.Job job) Communicate to the loader the location of the object(s) being loaded.
protected void	setValueType(Class<?> valueClass)
protected Object	translateWritableToPigDataType(org.apache.hadoop.io.Writable w, byte dataType)

Methods inherited from class org.apache.pig.FileInputLoadFunc

getSplitComparable

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getLoadCaster, getPathStrings, join, relativeToAbsolutePath, setUDFContextSignature

Methods inherited from class java.lang.Object

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

Field Detail

LOG

protected static final org.apache.commons.logging.Log LOG

mTupleFactory

protected TupleFactory mTupleFactory

serializationFactory

protected org.apache.hadoop.io.serializer.SerializationFactory serializationFactory

keyType

protected byte keyType

valType

protected byte valType

Constructor Detail

SequenceFileLoader

public SequenceFileLoader()

Method Detail

setKeyType

protected void setKeyType(Class<?> keyClass)
                   throws BackendException

Throws:

BackendException

setValueType

protected void setValueType(Class<?> valueClass)
                     throws BackendException

Throws:

BackendException

inferPigDataType

protected byte inferPigDataType(Type t)

translateWritableToPigDataType

protected Object translateWritableToPigDataType(org.apache.hadoop.io.Writable w,
                                                byte dataType)

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

getInputFormat

public org.apache.hadoop.mapreduce.InputFormat getInputFormat()
                                                       throws IOException

Description copied from class: LoadFunc

This will be called during planning on the front end. This is the instance of InputFormat (rather than the class name) because the load function may need to instantiate the InputFormat in order to control how it is constructed.

Specified by:

getInputFormat in class LoadFunc

Returns:

the InputFormat associated with this loader.

Throws:

IOException - if there is an exception during InputFormat construction

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.

Specified by:

prepareToRead in class LoadFunc

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

setLocation

public void setLocation(String location,
                        org.apache.hadoop.mapreduce.Job job)
                 throws IOException

Description copied from class: LoadFunc

Communicate to the loader the location of the object(s) being loaded. The location string passed to the LoadFunc here is the return value of LoadFunc.relativeToAbsolutePath(String, Path). Implementations should use this method to communicate the location (and any other information) to its underlying InputFormat through the Job object. This method will be called in the backend multiple times. Implementations should bear in mind that this method is called multiple times and should ensure there are no inconsistent side effects due to the multiple calls.

Specified by:

setLocation in class LoadFunc

Parameters:

location - Location as returned by LoadFunc.relativeToAbsolutePath(String, Path)

job - the Job object store or retrieve earlier stored information from the UDFContext

Throws:

IOException - if the location is not valid.