org.apache.hadoop.zebra.pig

Class TableLoader

java.lang.Object

org.apache.pig.LoadFunc

org.apache.hadoop.zebra.pig.TableLoader

All Implemented Interfaces:

CollectableLoadFunc, IndexableLoadFunc, LoadMetadata, LoadPushDown, OrderedLoadFunc

public class TableLoader
extends LoadFunc
implements LoadMetadata, LoadPushDown, IndexableLoadFunc, CollectableLoadFunc, OrderedLoadFunc

Pig IndexableLoadFunc and Slicer for Zebra Table

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.pig.LoadPushDown

LoadPushDown.OperatorSet, LoadPushDown.RequiredField, LoadPushDown.RequiredFieldList, LoadPushDown.RequiredFieldResponse

Constructor Summary

Constructors

Constructor and Description
TableLoader() default constructor
TableLoader(String projectionStr)
TableLoader(String projectionStr, String sorted)

Method Summary

Methods

Modifier and Type	Method and Description
void	close() A method called by the Pig runtime to give an opportunity for implementations to perform cleanup actions like closing the underlying input stream.
void	ensureAllKeyInstancesInSameSplit() When this method is called, Pig is communicating to the Loader that it must load data such that all instances of a key are in same split.
List<LoadPushDown.OperatorSet>	getFeatures() Determine the operators that can be pushed to the loader.
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.
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.
org.apache.hadoop.io.WritableComparable<?>	getSplitComparable(org.apache.hadoop.mapreduce.InputSplit split) The WritableComparable object returned will be used to compare the position of different splits in an ordered stream
ResourceStatistics	getStatistics(String location, org.apache.hadoop.mapreduce.Job job) Get statistics about the data to be loaded.
void	initialize(org.apache.hadoop.conf.Configuration conf) This method is called by Pig run time to allow the IndexableLoadFunc to perform any initialization actions
void	prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader, PigSplit split) Initializes LoadFunc for reading data.
LoadPushDown.RequiredFieldResponse	pushProjection(LoadPushDown.RequiredFieldList requiredFieldList) Indicate to the loader fields that will be needed.
void	seekNear(Tuple tuple) This method is called only once.
void	setLocation(String location, org.apache.hadoop.mapreduce.Job job) This method is called by pig on both frontend and backend.
void	setPartitionFilter(Expression partitionFilter) Set the filter for partitioning.
void	setUDFContextSignature(String signature) This method will be called by Pig both in the front end and back end to pass a unique signature to the LoadFunc.

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getLoadCaster, getPathStrings, join, relativeToAbsolutePath, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

TableLoader

public TableLoader()

default constructor

TableLoader

public TableLoader(String projectionStr)

Parameters:

projectionStr - projection string passed from pig query.

TableLoader

public TableLoader(String projectionStr,
           String sorted)
            throws IOException

Parameters:

projectionStr - projection string passed from pig query.

sorted - need sorted table(s)?

Throws:

IOException

Method Detail

initialize

public void initialize(org.apache.hadoop.conf.Configuration conf)
                throws IOException

Description copied from interface: IndexableLoadFunc

This method is called by Pig run time to allow the IndexableLoadFunc to perform any initialization actions

Specified by:

initialize in interface IndexableLoadFunc

Parameters:

conf - The job configuration object

Throws:

IOException

seekNear

public void seekNear(Tuple tuple)
              throws IOException

This method is called only once.

Specified by:

seekNear in interface IndexableLoadFunc

Parameters:

tuple - Tuple with join keys (which are a prefix of the sort keys of the input data). For example if the data is sorted on columns in position 2,4,5 any of the following Tuples are valid as an argument value: (fieldAt(2)) (fieldAt(2), fieldAt(4)) (fieldAt(2), fieldAt(4), fieldAt(5)) The following are some invalid cases: (fieldAt(4)) (fieldAt(2), fieldAt(5)) (fieldAt(4), fieldAt(5))

Throws:

IOException - When the loadFunc is unable to position to the required point in its input stream

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

close

public void close()
           throws IOException

Description copied from interface: IndexableLoadFunc

A method called by the Pig runtime to give an opportunity for implementations to perform cleanup actions like closing the underlying input stream. This is necessary since while performing a join the Pig run time may determine than no further join is possible with remaining records and may indicate to the IndexableLoader to cleanup by calling this method.

Specified by:

close in interface IndexableLoadFunc

Throws:

IOException - if the loadfunc is unable to perform its close actions.

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

This method is called by pig on both frontend and backend.

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.

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

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

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

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.

getFeatures

public List<LoadPushDown.OperatorSet> getFeatures()

Description copied from interface: LoadPushDown

Determine the operators that can be pushed to the loader. Note that by indicating a loader can accept a certain operator (such as selection) the loader is not promising that it can handle all selections. When it is passed the actual operators to push down it will still have a chance to reject them.

Specified by:

getFeatures in interface LoadPushDown

Returns:

list of all features that the loader can support

pushProjection

public LoadPushDown.RequiredFieldResponse pushProjection(LoadPushDown.RequiredFieldList requiredFieldList)
                                                  throws FrontendException

Description copied from interface: LoadPushDown

Indicate to the loader fields that will be needed. This can be useful for loaders that access data that is stored in a columnar format where indicating columns to be accessed a head of time will save scans. This method will not be invoked by the Pig runtime if all fields are required. So implementations should assume that if this method is not invoked, then all fields from the input are required. If the loader function cannot make use of this information, it is free to ignore it by returning an appropriate Response

Specified by:

pushProjection in interface LoadPushDown

Parameters:

requiredFieldList - RequiredFieldList indicating which columns will be needed. This structure is read only. User cannot make change to it inside pushProjection.

Returns:

Indicates which fields will be returned

Throws:

FrontendException

setUDFContextSignature

public void setUDFContextSignature(String signature)

Description copied from class: LoadFunc

This method will be called by Pig both in the front end and back end to pass a unique signature to the LoadFunc. The signature can be used to store into the UDFContext any information which the LoadFunc needs to store between various method invocations in the front end and back end. A use case is to store LoadPushDown.RequiredFieldList passed to it in LoadPushDown.pushProjection(RequiredFieldList) for use in the back end before returning tuples in LoadFunc.getNext(). This method will be call before other methods in LoadFunc

Overrides:

setUDFContextSignature in class LoadFunc

Parameters:

signature - a unique signature to identify this LoadFunc

getSplitComparable

public org.apache.hadoop.io.WritableComparable<?> getSplitComparable(org.apache.hadoop.mapreduce.InputSplit split)
                                                              throws IOException

Description copied from interface: OrderedLoadFunc

The WritableComparable object returned will be used to compare the position of different splits in an ordered stream

Specified by:

getSplitComparable in interface OrderedLoadFunc

Parameters:

split - An InputSplit from the InputFormat underlying this loader.

Returns:

WritableComparable representing the position of the split in input

Throws:

IOException

ensureAllKeyInstancesInSameSplit

public void ensureAllKeyInstancesInSameSplit()
                                      throws IOException

Description copied from interface: CollectableLoadFunc

When this method is called, Pig is communicating to the Loader that it must load data such that all instances of a key are in same split. Pig will make no further checks at runtime to ensure whether the contract is honored or not.

Specified by:

ensureAllKeyInstancesInSameSplit in interface CollectableLoadFunc

Throws:

IOException