org.apache.pig

Class LoadFuncMetadataWrapper

java.lang.Object

org.apache.pig.LoadFunc

org.apache.pig.LoadFuncWrapper

org.apache.pig.LoadFuncMetadataWrapper

All Implemented Interfaces:

LoadMetadata

Direct Known Subclasses:

ParquetLoader

public class LoadFuncMetadataWrapper
extends LoadFuncWrapper
implements LoadMetadata

Convenience class to extend when decorating a class that extends LoadFunc and implements LoadMetadata.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LoadFuncMetadataWrapper()

Method Summary

Methods

Modifier and Type	Method and Description
String[]	getPartitionKeys(String location, org.apache.hadoop.mapreduce.Job job) Find what columns are partition keys for this input.
ResourceSchema	getSchema(String location, org.apache.hadoop.mapreduce.Job job) Get a schema for the data to be loaded.
ResourceStatistics	getStatistics(String location, org.apache.hadoop.mapreduce.Job job) Get statistics about the data to be loaded.
protected void	setLoadFunc(LoadMetadata loadFunc) The wrapped LoadMetadata object must be set before method calls are made on this object.
void	setPartitionFilter(Expression partitionFilter) Set the filter for partitioning.

Methods inherited from class org.apache.pig.LoadFuncWrapper

getInputFormat, getLoadCaster, getMethodName, getNext, loadFunc, prepareToRead, relativeToAbsolutePath, setLoadFunc, setLocation, setUDFContextSignature

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getCacheFiles, getPathStrings, getShipFiles, join, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

LoadFuncMetadataWrapper

protected LoadFuncMetadataWrapper()

Method Detail

setLoadFunc

protected void setLoadFunc(LoadMetadata loadFunc)

The wrapped LoadMetadata object must be set before method calls are made on this object. Typically, this is done with via constructor, but often times the wrapped object can not be properly initialized until later in the lifecycle of the wrapper object.

Parameters:

loadFunc -

getSchema

public ResourceSchema getSchema(String location,
                       org.apache.hadoop.mapreduce.Job job)
                         throws IOException

Description copied from interface: LoadMetadata

Get a schema for the data to be loaded.

Specified by:

getSchema in interface LoadMetadata

Parameters:

location - Location as returned by LoadFunc.relativeToAbsolutePath(String, org.apache.hadoop.fs.Path)

job - The Job object - this should be used only to obtain cluster properties through JobContextImpl.getConfiguration() and not to set/query any runtime job information.

Returns:

schema for the data to be loaded. This schema should represent all tuples of the returned data. If the schema is unknown or it is not possible to return a schema that represents all returned data, then null should be returned. The schema should not be affected by pushProjection, ie. getSchema should always return the original schema even after pushProjection

Throws:

IOException - if an exception occurs while determining the schema

getStatistics

public ResourceStatistics getStatistics(String location,
                               org.apache.hadoop.mapreduce.Job job)
                                 throws IOException

Description copied from interface: LoadMetadata

Get statistics about the data to be loaded. If no statistics are available, then null should be returned. If the implementing class also extends LoadFunc, then LoadFunc.setLocation(String, org.apache.hadoop.mapreduce.Job) is guaranteed to be called before this method.

Specified by:

getStatistics in interface LoadMetadata

Parameters:

location - Location as returned by LoadFunc.relativeToAbsolutePath(String, org.apache.hadoop.fs.Path)

job - The Job object - this should be used only to obtain cluster properties through JobContextImpl.getConfiguration() and not to set/query any runtime job information.

Returns:

statistics about the data to be loaded. If no statistics are available, then null should be returned.

Throws:

IOException - if an exception occurs while retrieving statistics

getPartitionKeys

public String[] getPartitionKeys(String location,
                        org.apache.hadoop.mapreduce.Job job)
                          throws IOException

Description copied from interface: LoadMetadata

Find what columns are partition keys for this input.

Specified by:

getPartitionKeys in interface LoadMetadata

Parameters:

location - Location as returned by LoadFunc.relativeToAbsolutePath(String, org.apache.hadoop.fs.Path)

job - The Job object - this should be used only to obtain cluster properties through JobContextImpl.getConfiguration() and not to set/query any runtime job information.

Returns:

array of field names of the partition keys. Implementations should return null to indicate that there are no partition keys

Throws:

IOException - if an exception occurs while retrieving partition keys

setPartitionFilter

public void setPartitionFilter(Expression partitionFilter)
                        throws IOException

Description copied from interface: LoadMetadata

Set the filter for partitioning. It is assumed that this filter will only contain references to fields given as partition keys in getPartitionKeys. So if the implementation returns null in LoadMetadata.getPartitionKeys(String, Job), then this method is not called by Pig runtime. This method is also not called by the Pig runtime if there are no partition filter conditions.

Specified by:

setPartitionFilter in interface LoadMetadata

Parameters:

partitionFilter - that describes filter for partitioning

Throws:

IOException - if the filter is not compatible with the storage mechanism or contains non-partition fields.