org.apache.pig.piggybank.storage
Class AllLoader

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

All Implemented Interfaces:

LoadMetadata, LoadPushDown, OrderedLoadFunc, StoreMetadata

public class AllLoader
extends FileInputLoadFunc
implements LoadMetadata, StoreMetadata, LoadPushDown

The AllLoader provides the ability to point pig at a folder that contains files in multiple formats e.g. PlainText, Gz, Bz, Lzo, HiveRC etc and have the LoadFunc(s) automatically selected based on the file extension.
How this works:
The file extensions are mapped in the pig.properties via the property file.extension.loaders.

file.extension.loaders format

• [file extension]:[loader func spec]
• [file-extension]:[optional path tag]:[loader func spec]
• [file-extension]:[optional path tag]:[sequence file key value writer class name]:[loader func spec]

The file.extension.loaders property associate pig loaders with file extensions, if a file does not have an extension the AllLoader will look at the first three bytes of a file and try to guess its format bassed on:

• [ -119, 76, 90 ] = lzo
• [ 31, -117, 8 ] = gz
• [ 66, 90, 104 ] = bz2
• [ 83, 69, 81 ] = seq

The loader associated with that extension will then be used.

Path partitioning The AllLoader supports hive style path partitioning e.g. /log/type1/daydate=2010-11-01
"daydate" will be considered a partition key and filters can be written against this.
Note that the filter should go into the AllLoader contructor e.g.
a = LOAD 'input' using AllLoader('daydate<\"2010-11-01\"')
Path tags AllLoader supports configuring different loaders for the same extension based on there file path.
E.g.
We have the paths /log/type1, /log/type2
For each of these directories we'd like to use different loaders.
So we use setup our loaders:
file.extension.loaders:gz:type1:MyType1Loader, gz:type2:MyType2Loader

Sequence files Sequence files also support using the Path tags for loader selection but has an extra configuration option that relates to the Key Class used to write the Sequence file.
E.g. for HiveRC this value is: org.apache.hadoop.hive.ql.io.RCFile so we can setup our sequence file formatting:
file.extension.loaders:seq::org.apache.hadoop.hive.ql.io.RCFile: MyHiveRCLoader, seq::DefaultSequenceFileLoader

Schema The JsoneMetadata schema loader is supported and the schema will be loaded using this loader.
In case this fails, the schema can be loaded using the default schema provided.

Nested Class Summary

static class	AllLoader.AllLoaderInputFormat InputFormat that encapsulates the correct input format based on the file type.
static class	AllLoader.AllReader This is where the logic is for selecting the correct Loader.

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

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

Constructor Summary

AllLoader()

AllLoader(String partitionFilter)

Method Summary

List<LoadPushDown.OperatorSet>	getFeatures() Determine the operators that can be pushed to the loader.
AllLoader.AllLoaderInputFormat	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.
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.
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	setLocation(String location, org.apache.hadoop.mapreduce.Job job) Communicate to the loader the location of the object(s) being loaded.
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.
void	storeSchema(ResourceSchema schema, String location, org.apache.hadoop.mapreduce.Job job) Store schema of the data being written
void	storeStatistics(ResourceStatistics stats, String location, org.apache.hadoop.mapreduce.Job job) Store statistics about the data being written.

Methods inherited from class org.apache.pig.FileInputLoadFunc

getSplitComparable

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getPathStrings, join, relativeToAbsolutePath, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

AllLoader

public AllLoader()

AllLoader

public AllLoader(String partitionFilter)

Method Detail

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.

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

getInputFormat

public AllLoader.AllLoaderInputFormat 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

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

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

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 JobContext.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 JobContext.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

storeStatistics

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

Description copied from interface: StoreMetadata

Store statistics about the data being written.

Specified by:

storeStatistics in interface StoreMetadata

Parameters:

stats - statistics to be recorded

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 JobContext.getConfiguration() and not to set/query any runtime job information.

Throws:

IOException

storeSchema

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

Description copied from interface: StoreMetadata

Store schema of the data being written

Specified by:

storeSchema in interface StoreMetadata

Parameters:

schema - Schema to be recorded

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 JobContext.getConfiguration() and not to set/query any runtime job information.

Throws:

IOException

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 JobContext.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

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

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.