org.apache.pig.piggybank.storage
Class RegExLoader

java.lang.Object
  extended by org.apache.pig.LoadFunc
      extended by org.apache.pig.piggybank.storage.RegExLoader
Direct Known Subclasses:
CombinedLogLoader, CommonLogLoader, MyRegExLoader

public abstract class RegExLoader
extends LoadFunc

RegExLoader is an abstract class used to parse logs based on a regular expression. There is a single abstract method, getPattern which needs to return a Pattern. Each group will be returned as a different DataAtom. Look to org.apache.pig.piggybank.storage.apachelog.CommonLogLoader for example usage.


Constructor Summary
RegExLoader()
           
 
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.
abstract  Pattern getPattern()
           
 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, getLoadCaster, 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

RegExLoader

public RegExLoader()
Method Detail

getPattern

public abstract Pattern getPattern()

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 frontend and 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.


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