org.apache.pig.piggybank.storage

Class CSVExcelStorage

java.lang.Object

org.apache.pig.LoadFunc

org.apache.pig.FileInputLoadFunc

org.apache.pig.builtin.PigStorage

org.apache.pig.piggybank.storage.CSVExcelStorage

All Implemented Interfaces:

LoadMetadata, LoadPushDown, OrderedLoadFunc, OverwritableStoreFunc, StoreFuncInterface, StoreMetadata

public class CSVExcelStorage
extends PigStorage
implements StoreFuncInterface, LoadPushDown

CSV loading and storing with support for multi-line fields, and escaping of delimiters and double quotes within fields; uses CSV conventions of Excel 2007. Arguments allow for control over: Which field delimiter to use (default = ',') Whether line breaks are allowed inside of fields (YES_MULTILINE = yes, NO_MULTILINE = no, default = no) How line breaks are to be written when storing (UNIX = LF, WINDOWS = CRLF, NOCHANGE = system default, default = system default) What to do with header rows (first line of each file): On load: READ_INPUT_HEADER = read header rows, SKIP_INPUT_HEADER = do not read header rows, default = read header rows On store: WRITE_OUTPUT_HEADER = write a header row, SKIP_OUTPUT_HEADER = do not write a header row, default = do not write a header row Usage: STORE x INTO '' USING org.apache.pig.piggybank.storage.CSVExcelStorage( [DELIMITER[, {YES_MULTILINE | NO_MULTILINE}[, {UNIX | WINDOWS | NOCHANGE}[, {READ_INPUT_HEADER, SKIP_INPUT_HEADER, WRITE_OUTPUT_HEADER, SKIP_OUTPUT_HEADER}]]]] ); Linebreak settings are only used during store; during load, no conversion is performed. WARNING: A danger with enabling multiline fields during load is that unbalanced double quotes will cause slurping up of input until a balancing double quote is found, or until something breaks. If you are not expecting newlines within fields it is therefore more robust to use NO_MULTILINE, which is the default for that reason. This is Adreas Paepcke's CSVExcelStorage with a few modifications.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CSVExcelStorage.Headers
static class	CSVExcelStorage.Linebreaks
static class	CSVExcelStorage.Multiline

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 static byte	CARRIAGE_RETURN
protected static byte	DOUBLE_QUOTE
protected org.apache.hadoop.mapreduce.RecordReader	in
protected static byte	LINEFEED
protected static byte	RECORD_DEL
protected ResourceSchema	schema

Fields inherited from class org.apache.pig.builtin.PigStorage

caster, mLog, signature, writer

Constructor Summary

Constructors

Constructor and Description
CSVExcelStorage()
CSVExcelStorage(String delimiter)
CSVExcelStorage(String delimiter, String multilineTreatmentStr)
CSVExcelStorage(String delimiter, String multilineTreatmentStr, String eolTreatmentStr)
CSVExcelStorage(String delimiter, String multilineTreatmentStr, String eolTreatmentStr, String headerTreatmentStr)

Method Summary

Modifier and Type	Method and Description
void	checkSchema(ResourceSchema s) Set the schema for data to be stored.
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.
void	prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader, PigSplit split) Initializes LoadFunc for reading data.
void	prepareToWrite(org.apache.hadoop.mapreduce.RecordWriter writer) Initialize StoreFuncInterface to write data.
LoadPushDown.RequiredFieldResponse	pushProjection(LoadPushDown.RequiredFieldList requiredFieldList) Indicate to the loader fields that will be needed.
void	putNext(Tuple tupleToWrite) Write a tuple to the data store.
void	setLocation(String location, org.apache.hadoop.mapreduce.Job job) Communicate to the loader the location of the object(s) being loaded.
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	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.builtin.PigStorage

cleanupOnFailure, cleanupOnSuccess, cleanupOutput, equals, equals, getOutputFormat, getPartitionKeys, getSchema, getStatistics, hashCode, readField, relToAbsPathForStoreLocation, setPartitionFilter, setStoreLocation, shouldOverwrite, storeSchema, storeStatistics

Methods inherited from class org.apache.pig.FileInputLoadFunc

getSplitComparable

Methods inherited from class org.apache.pig.LoadFunc

getAbsolutePath, getCacheFiles, getLoadCaster, getPathStrings, getShipFiles, join, relativeToAbsolutePath, warn

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.pig.StoreFuncInterface

cleanupOnFailure, cleanupOnSuccess, getOutputFormat, relToAbsPathForStoreLocation, setStoreLocation

Field Detail

LINEFEED

protected static final byte LINEFEED

See Also:

Constant Field Values

CARRIAGE_RETURN

protected static final byte CARRIAGE_RETURN

See Also:

Constant Field Values

DOUBLE_QUOTE

protected static final byte DOUBLE_QUOTE

See Also:

Constant Field Values

RECORD_DEL

protected static final byte RECORD_DEL

See Also:

Constant Field Values

in

protected org.apache.hadoop.mapreduce.RecordReader in

schema

protected ResourceSchema schema

Constructor Detail

CSVExcelStorage

public CSVExcelStorage()

CSVExcelStorage

public CSVExcelStorage(String delimiter)

CSVExcelStorage

public CSVExcelStorage(String delimiter,
                       String multilineTreatmentStr)

CSVExcelStorage

public CSVExcelStorage(String delimiter,
                       String multilineTreatmentStr,
                       String eolTreatmentStr)

CSVExcelStorage

public CSVExcelStorage(String delimiter,
                       String multilineTreatmentStr,
                       String eolTreatmentStr,
                       String headerTreatmentStr)

Method Detail

checkSchema

public void checkSchema(ResourceSchema s)
                 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

Overrides:

checkSchema in class PigStorage

Parameters:

s - 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.

prepareToWrite

public void prepareToWrite(org.apache.hadoop.mapreduce.RecordWriter writer)

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

Overrides:

prepareToWrite in class PigStorage

Parameters:

writer - RecordWriter to use.

putNext

public void putNext(Tuple tupleToWrite)
             throws IOException

Description copied from interface: StoreFuncInterface

Write a tuple to the data store.

Specified by:

putNext in interface StoreFuncInterface

Overrides:

putNext in class PigStorage

Parameters:

tupleToWrite - the tuple to store.

Throws:

IOException - if an exception occurs during the write

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.

Overrides:

getNext in class PigStorage

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

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.

Overrides:

setLocation in class PigStorage

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()

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.

Overrides:

getInputFormat in class PigStorage

Returns:

the InputFormat associated with this loader.

prepareToRead

public void prepareToRead(org.apache.hadoop.mapreduce.RecordReader reader,
                          PigSplit split)

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.

Overrides:

prepareToRead in class PigStorage

Parameters:

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

split - The input PigSplit to process

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

Overrides:

pushProjection in class PigStorage

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 PigStorage

Parameters:

signature - a unique signature to identify this LoadFunc

setStoreFuncUDFContextSignature

public 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

Overrides:

setStoreFuncUDFContextSignature in class PigStorage

Parameters:

signature - a unique signature to identify this StoreFuncInterface

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

Overrides:

getFeatures in class PigStorage

Returns:

list of all features that the loader can support