org.apache.pig.builtin

Class AvroStorage

java.lang.Object

org.apache.pig.LoadFunc

org.apache.pig.builtin.AvroStorage

All Implemented Interfaces:

LoadMetadata, LoadPushDown, StoreFuncInterface, StoreResources

Direct Known Subclasses:

TrevniStorage

public class AvroStorage
extends LoadFunc
implements StoreFuncInterface, LoadMetadata, LoadPushDown, StoreResources

Pig UDF for reading and writing Avro data.

Nested Class Summary

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

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

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	allowRecursive
protected boolean	doubleColonsToDoubleUnderscores
static String	INPUT_AVRO_SCHEMA Pig property name for the input avro schema.
protected org.apache.commons.logging.Log	log
static String	OUTPUT_AVRO_SCHEMA Pig property name for the output avro schema.
protected LoadPushDown.RequiredFieldList	requiredFieldList List of required fields passed by pig in a push down projection.
protected org.apache.avro.Schema	schema
protected String	udfContextSignature Context signature for this UDF instance.

Constructor Summary

Constructors

Constructor and Description
AvroStorage() Creates new instance of Pig Storage function, without specifying the schema.
AvroStorage(String sn) Creates new instance of Pig Storage function.
AvroStorage(String sn, String opts) Creates new instance of AvroStorage function, specifying output schema properties.

Method Summary

Modifier and Type	Method and Description
void	checkSchema(ResourceSchema rs) Set the schema for data to be stored.
void	cleanupOnFailure(String location, org.apache.hadoop.mapreduce.Job job) This method will be called by Pig if the job which contains this store fails.
void	cleanupOnSuccess(String location, org.apache.hadoop.mapreduce.Job job) This method will be called by Pig if the job which contains this store is successful, and some cleanup of intermediate resources is required.
org.apache.avro.Schema	getAvroSchema(org.apache.hadoop.fs.Path[] p, org.apache.hadoop.mapreduce.Job job) Reads the avro schemas at the specified location.
protected org.apache.avro.Schema	getAvroSchema(String location, org.apache.hadoop.mapreduce.Job job) Reads the avro schema at the specified location.
List<LoadPushDown.OperatorSet>	getFeatures() Determine the operators that can be pushed to the loader.
org.apache.avro.Schema	getInputAvroSchema() Helper function reads the input avro schema from the UDF Properties.
org.apache.hadoop.mapreduce.InputFormat<org.apache.hadoop.io.NullWritable,org.apache.avro.generic.GenericData.Record>	getInputFormat() This will be called during planning on the front end.
Tuple	getNext() Retrieves the next tuple to be processed.
protected org.apache.avro.Schema	getOutputAvroSchema() Utility function that gets the output schema from the udf properties for this instance of the store function.
org.apache.hadoop.mapreduce.OutputFormat<org.apache.hadoop.io.NullWritable,Object>	getOutputFormat() Return the OutputFormat associated with StoreFuncInterface.
String[]	getPartitionKeys(String location, org.apache.hadoop.mapreduce.Job job) Find what columns are partition keys for this input.
protected Properties	getProperties() Internal function for getting the Properties object associated with this UDF instance.
protected Properties	getProperties(Class c, String signature) Internal function for getting the Properties object associated with this UDF instance.
ResourceSchema	getSchema(String location, org.apache.hadoop.mapreduce.Job job) Get a schema for the data to be loaded.
List<String>	getShipFiles() Allow a LoadFunc to specify a list of files located locally and would like to ship to backend (through distributed cache).
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 r, PigSplit s) Initializes LoadFunc for reading data.
void	prepareToWrite(org.apache.hadoop.mapreduce.RecordWriter w) Initialize StoreFuncInterface to write data.
LoadPushDown.RequiredFieldResponse	pushProjection(LoadPushDown.RequiredFieldList rfl) Indicate to the loader fields that will be needed.
void	putNext(Tuple t) Write a tuple to the data store.
String	relToAbsPathForStoreLocation(String location, org.apache.hadoop.fs.Path curDir) This method is called by the Pig runtime in the front end to convert the output location to an absolute path if the location is relative.
protected void	setInputAvroSchema(org.apache.avro.Schema s) Sets the input avro schema to .
void	setLocation(String location, org.apache.hadoop.mapreduce.Job job) Communicate to the loader the location of the object(s) being loaded.
protected void	setOutputAvroSchema(org.apache.avro.Schema s) Sets the output avro schema to .
void	setPartitionFilter(Expression partitionFilter) Set the filter for partitioning.
void	setStoreFuncUDFContextSignature(String signature) This method will be called by Pig both in the front end and back end to pass a unique signature to the StoreFuncInterface which it can use to store information in the UDFContext which it needs to store between various method invocations in the front end and back end.
void	setStoreLocation(String location, org.apache.hadoop.mapreduce.Job job) Communicate to the storer the location where the data needs to be stored.
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, getCacheFiles, getLoadCaster, getPathStrings, join, relativeToAbsolutePath, warn

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.pig.StoreResources

getCacheFiles

Field Detail

allowRecursive

protected boolean allowRecursive

doubleColonsToDoubleUnderscores

protected boolean doubleColonsToDoubleUnderscores

schema

protected org.apache.avro.Schema schema

log

protected final org.apache.commons.logging.Log log

udfContextSignature

protected String udfContextSignature

Context signature for this UDF instance.

OUTPUT_AVRO_SCHEMA

public static final String OUTPUT_AVRO_SCHEMA

Pig property name for the output avro schema.

See Also:

Constant Field Values

INPUT_AVRO_SCHEMA

public static final String INPUT_AVRO_SCHEMA

Pig property name for the input avro schema.

See Also:

Constant Field Values

requiredFieldList

protected LoadPushDown.RequiredFieldList requiredFieldList

List of required fields passed by pig in a push down projection.

Constructor Detail

AvroStorage

public AvroStorage()

Creates new instance of Pig Storage function, without specifying the schema. Useful for just loading in data.

AvroStorage

public AvroStorage(String sn)

Creates new instance of Pig Storage function.

Parameters:

sn - Specifies the input/output schema or record name.

AvroStorage

public AvroStorage(String sn,
                   String opts)

Creates new instance of AvroStorage function, specifying output schema properties.

Parameters:

sn - Specifies the input/output schema or record name.

opts - Options for AvroStorage:

-namespace Namespace for an automatically generated output schema.

-schemafile Specifies URL for avro schema file from which to read the input schema (can be local file, hdfs, url, etc).

-schemaclass Specifies fully qualified class name for avro class in your classpath which implements GenericContainer.

-examplefile Specifies URL for avro data file from which to copy the input schema (can be local file, hdfs, url, etc).

-allowrecursive Option to allow recursive schema definitions (default is false).

-doublecolons Option to translate Pig schema names with double colons to names with double underscores (default is false).

Method Detail

setUDFContextSignature

public final 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

getProperties

protected final Properties getProperties()

Internal function for getting the Properties object associated with this UDF instance.

Returns:

The Properties object associated with this UDF instance

getProperties

protected final Properties getProperties(Class c,
                                         String signature)

Internal function for getting the Properties object associated with this UDF instance.

Parameters:

c - Class of this UDF

signature - Signature string

Returns:

The Properties object associated with this UDF instance

getSchema

public final 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

getAvroSchema

protected final org.apache.avro.Schema getAvroSchema(String location,
                                                     org.apache.hadoop.mapreduce.Job job)
                                              throws IOException

Reads the avro schema at the specified location.

Parameters:

location - Location of file

job - Hadoop job object

Returns:

an Avro Schema object derived from the specified file

Throws:

IOException

getAvroSchema

public org.apache.avro.Schema getAvroSchema(org.apache.hadoop.fs.Path[] p,
                                            org.apache.hadoop.mapreduce.Job job)
                                     throws IOException

Reads the avro schemas at the specified location.

Parameters:

p - Location of file

job - Hadoop job object

Returns:

an Avro Schema object derived from the specified file

Throws:

IOException

getStatistics

public final 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 final 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.

relToAbsPathForStoreLocation

public final String relToAbsPathForStoreLocation(String location,
                                                 org.apache.hadoop.fs.Path curDir)
                                          throws IOException

Description copied from interface: StoreFuncInterface

This method is called by the Pig runtime in the front end to convert the output location to an absolute path if the location is relative. The StoreFuncInterface implementation is free to choose how it converts a relative location to an absolute location since this may depend on what the location string represent (hdfs path or some other data source). The static method LoadFunc.getAbsolutePath(java.lang.String, org.apache.hadoop.fs.Path) provides a default implementation for hdfs and hadoop local file system and it can be used to implement this method.

Specified by:

relToAbsPathForStoreLocation in interface StoreFuncInterface

Parameters:

location - location as provided in the "store" statement of the script

curDir - the current working direction based on any "cd" statements in the script before the "store" statement. If there are no "cd" statements in the script, this would be the home directory -

/user/ 

Returns:

the absolute location based on the arguments passed

Throws:

IOException - if the conversion is not possible

getOutputFormat

public org.apache.hadoop.mapreduce.OutputFormat<org.apache.hadoop.io.NullWritable,Object> getOutputFormat()
                                                                                                   throws IOException

Description copied from interface: StoreFuncInterface

Return the OutputFormat associated with StoreFuncInterface. This will be called on the front end during planning and on the backend during execution.

Specified by:

getOutputFormat in interface StoreFuncInterface

Returns:

the OutputFormat associated with StoreFuncInterface

Throws:

IOException - if an exception occurs while constructing the OutputFormat

setStoreLocation

public final void setStoreLocation(String location,
                                   org.apache.hadoop.mapreduce.Job job)
                            throws IOException

Description copied from interface: StoreFuncInterface

Communicate to the storer the location where the data needs to be stored. The location string passed to the StoreFuncInterface here is the return value of StoreFuncInterface.relToAbsPathForStoreLocation(String, Path) 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. StoreFuncInterface.checkSchema(ResourceSchema) will be called before any call to StoreFuncInterface.setStoreLocation(String, Job).

Specified by:

setStoreLocation in interface StoreFuncInterface

Parameters:

location - Location returned by StoreFuncInterface.relToAbsPathForStoreLocation(String, Path)

job - The Job object

Throws:

IOException - if the location is not valid.

checkSchema

public final void checkSchema(ResourceSchema rs)
                       throws IOException

Description copied from interface: StoreFuncInterface

Set the schema for data to be stored. This will be called on the front end during planning if the store is associated with a schema. A Store function should implement this function to check that a given schema is acceptable to it. For example, it can check that the correct partition keys are included; a storage function to be written directly to an OutputFormat can make sure the schema will translate in a well defined way.

Specified by:

checkSchema in interface StoreFuncInterface

Parameters:

rs - to be checked

Throws:

IOException - if this schema is not acceptable. It should include a detailed error message indicating what is wrong with the schema.

setOutputAvroSchema

protected final void setOutputAvroSchema(org.apache.avro.Schema s)

Sets the output avro schema to .

Parameters:

s - An Avro schema

getOutputAvroSchema

protected final org.apache.avro.Schema getOutputAvroSchema()

Utility function that gets the output schema from the udf properties for this instance of the store function.

Returns:

the output schema associated with this UDF

prepareToWrite

public final void prepareToWrite(org.apache.hadoop.mapreduce.RecordWriter w)
                          throws IOException

Description copied from interface: StoreFuncInterface

Initialize StoreFuncInterface to write data. This will be called during execution before the call to putNext.

Specified by:

prepareToWrite in interface StoreFuncInterface

Parameters:

w - RecordWriter to use.

Throws:

IOException - if an exception occurs during initialization

putNext

public final void putNext(Tuple t)
                   throws IOException

Description copied from interface: StoreFuncInterface

Write a tuple to the data store.

Specified by:

putNext in interface StoreFuncInterface

Parameters:

t - the tuple to store.

Throws:

IOException - if an exception occurs during the write

setStoreFuncUDFContextSignature

public final void setStoreFuncUDFContextSignature(String signature)

Description copied from interface: StoreFuncInterface

This method will be called by Pig both in the front end and back end to pass a unique signature to the StoreFuncInterface which it can use to store information in the UDFContext which it needs to store between various method invocations in the front end and back end. This is necessary because in a Pig Latin script with multiple stores, the different instances of store functions need to be able to find their (and only their) data in the UDFContext object.

Specified by:

setStoreFuncUDFContextSignature in interface StoreFuncInterface

Parameters:

signature - a unique signature to identify this StoreFuncInterface

cleanupOnFailure

public final void cleanupOnFailure(String location,
                                   org.apache.hadoop.mapreduce.Job job)
                            throws IOException

Description copied from interface: StoreFuncInterface

This method will be called by Pig if the job which contains this store fails. Implementations can clean up output locations in this method to ensure that no incorrect/incomplete results are left in the output location

Specified by:

cleanupOnFailure in interface StoreFuncInterface

Parameters:

location - Location returned by StoreFuncInterface.relToAbsPathForStoreLocation(String, 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.

Throws:

IOException

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.

setInputAvroSchema

protected final void setInputAvroSchema(org.apache.avro.Schema s)

Sets the input avro schema to .

Parameters:

s - The specified schema

getInputAvroSchema

public final org.apache.avro.Schema getInputAvroSchema()

Helper function reads the input avro schema from the UDF Properties.

Returns:

The input avro schema

getInputFormat

public org.apache.hadoop.mapreduce.InputFormat<org.apache.hadoop.io.NullWritable,org.apache.avro.generic.GenericData.Record> 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

See Also:

LoadFunc.getInputFormat()

prepareToRead

public final void prepareToRead(org.apache.hadoop.mapreduce.RecordReader r,
                                PigSplit s)
                         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:

r - RecordReader to be used by this instance of the LoadFunc

s - The input PigSplit to process

Throws:

IOException - if there is an exception during initialization

getNext

public final 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

cleanupOnSuccess

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

Description copied from interface: StoreFuncInterface

This method will be called by Pig if the job which contains this store is successful, and some cleanup of intermediate resources is required. Implementations can clean up output locations in this method to ensure that no incorrect/incomplete results are left in the output location

Specified by:

cleanupOnSuccess in interface StoreFuncInterface

Parameters:

location - Location returned by StoreFuncInterface.relToAbsPathForStoreLocation(String, 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.

Throws:

IOException

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 rfl)
                                                  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:

rfl - 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

getShipFiles

public List<String> getShipFiles()

Description copied from class: LoadFunc

Allow a LoadFunc to specify a list of files located locally and would like to ship to backend (through distributed cache). Check for FuncUtils for utility function to facilitate it The default implementation returns null.

Specified by:

getShipFiles in interface StoreResources

Overrides:

getShipFiles in class LoadFunc

Returns:

A list of files