org.apache.pig.impl.io
Class ReadToEndLoader

java.lang.Object
  extended by org.apache.pig.LoadFunc
      extended by org.apache.pig.impl.io.ReadToEndLoader

public class ReadToEndLoader
extends LoadFunc

This is wrapper Loader which wraps a real LoadFunc underneath and allows to read a file completely starting a given split (indicated by a split index which is used to look in the List returned by the underlying InputFormat's getSplits() method). So if the supplied split index is 0, this loader will read the entire file. If it is non zero it will read the partial file beginning from that split to the last split. The call sequence to use this is: 1) construct an object using the constructor 2) Call getNext() in a loop till it returns null


Constructor Summary
ReadToEndLoader(LoadFunc wrappedLoadFunc, org.apache.hadoop.conf.Configuration conf, String inputLocation, int splitIndex)
           
ReadToEndLoader(LoadFunc wrappedLoadFunc, org.apache.hadoop.conf.Configuration conf, String inputLocation, int[] toReadSplitIdxs)
          This constructor takes an array of split indexes (toReadSplitIdxs) of the splits to be read.
 
Method Summary
 org.apache.hadoop.mapreduce.InputFormat getInputFormat()
          This will be called during planning on the front end.
 LoadCaster getLoadCaster()
          This will be called on the front end during planning and not on the back end during execution.
 Tuple getNext()
          Retrieves the next tuple to be processed.
 void prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader, PigSplit split)
          Initializes LoadFunc for reading data.
 void setLocation(String location, org.apache.hadoop.mapreduce.Job job)
          Communicate to the loader the location of the object(s) being loaded.
 
Methods inherited from class org.apache.pig.LoadFunc
getAbsolutePath, getPathStrings, join, relativeToAbsolutePath, setUDFContextSignature, warn
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ReadToEndLoader

public ReadToEndLoader(LoadFunc wrappedLoadFunc,
                       org.apache.hadoop.conf.Configuration conf,
                       String inputLocation,
                       int splitIndex)
                throws IOException
Parameters:
wrappedLoadFunc -
conf -
inputLocation -
splitIndex -
Throws:
IOException
InterruptedException

ReadToEndLoader

public ReadToEndLoader(LoadFunc wrappedLoadFunc,
                       org.apache.hadoop.conf.Configuration conf,
                       String inputLocation,
                       int[] toReadSplitIdxs)
                throws IOException
This constructor takes an array of split indexes (toReadSplitIdxs) of the splits to be read.

Parameters:
wrappedLoadFunc -
conf -
inputLocation -
toReadSplitIdxs -
Throws:
IOException
InterruptedException
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

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

getLoadCaster

public LoadCaster getLoadCaster()
                         throws IOException
Description copied from class: LoadFunc
This will be called on the front end during planning and not on the back end during execution.

Overrides:
getLoadCaster in class LoadFunc
Returns:
the LoadCaster associated with this loader. Returning null indicates that casts from byte array are not supported for this loader. construction
Throws:
IOException - if there is an exception during LoadCaster

prepareToRead

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

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.


Copyright © 2007-2012 The Apache Software Foundation