org.apache.datasketches.pig.cpc

Class DataToSketch

java.lang.Object

org.apache.pig.EvalFunc<org.apache.pig.data.DataByteArray>

org.apache.datasketches.pig.cpc.DataToSketch

All Implemented Interfaces:

org.apache.pig.Accumulator<org.apache.pig.data.DataByteArray>, org.apache.pig.Algebraic

public class DataToSketch
extends org.apache.pig.EvalFunc<org.apache.pig.data.DataByteArray>
implements org.apache.pig.Accumulator<org.apache.pig.data.DataByteArray>, org.apache.pig.Algebraic

This is a Pig UDF that builds sketches from data. This class implements both the Accumulator and Algebraic interfaces.

Author:

Alexander Saydakov

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.pig.EvalFunc

org.apache.pig.EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
DataToSketch() Constructor with default lgK and seed
DataToSketch(int lgK, long seed) Base constructor.
DataToSketch(String lgK) Constructor with given lgK as string and default seed
DataToSketch(String lgK, String seed) Constructor with given lgK and seed as strings

Method Summary

Modifier and Type	Method and Description
void	accumulate(org.apache.pig.data.Tuple inputTuple) An Accumulator version of the standard exec() method.
void	cleanup() Cleans up the UDF state after being called using the Accumulator interface.
org.apache.pig.data.DataByteArray	exec(org.apache.pig.data.Tuple inputTuple) Top-level exec function.
String	getFinal()
String	getInitial()
String	getIntermed()
org.apache.pig.data.DataByteArray	getValue() Returns the sketch that has been built up by multiple calls to accumulate(org.apache.pig.data.Tuple).

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLoadCaster, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, needEndOfAllInputProcessing, outputSchema, progress, setEndOfAllInput, setInputSchema, setPigLogger, setReporter, setUDFContextSignature, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

DataToSketch

public DataToSketch()

Constructor with default lgK and seed

DataToSketch

public DataToSketch(String lgK)

Constructor with given lgK as string and default seed

Parameters:

lgK - in a form of a String

DataToSketch

public DataToSketch(String lgK,
                    String seed)

Constructor with given lgK and seed as strings

Parameters:

lgK - in a form of a String

seed - in a form of a String

DataToSketch

public DataToSketch(int lgK,
                    long seed)

Base constructor.

Parameters:

lgK - parameter controlling the sketch size and accuracy

seed - parameter to use during hashing

Method Detail

exec

public org.apache.pig.data.DataByteArray exec(org.apache.pig.data.Tuple inputTuple)
                                       throws IOException

Top-level exec function. This method accepts an input Tuple containing a Bag of one or more inner Datum Tuples and returns a single serialized CpcSketch as a DataByteArray. Datum Tuple is a Tuple containing a single field, which can be one of the following (Java type: Pig type):

• Byte: BYTE
• Integer: INTEGER
• Long: LONG
• Float: FLOAT
• Double: DOUBLE
• String: CHARARRAY
• DataByteArray: BYTEARRAY

Note Strings as values are normally typed as DataType.CHARARRAY, which will be encoded as UTF-8 prior to being submitted to the sketch. If the user requires a different encoding for cross-platform compatibility, it is recommended that these values be encoded prior to being submitted in a DataBag and then typed as a DataType.BYTEARRAY.

Specified by:

exec in class org.apache.pig.EvalFunc<org.apache.pig.data.DataByteArray>

Parameters:

inputTuple - A tuple containing a single bag, containing Datum Tuples.

Returns:

serialized CpcSketch

Throws:

IOException - from Pig

See Also:

"org.apache.pig.EvalFunc.exec(org.apache.pig.data.Tuple)"

accumulate

public void accumulate(org.apache.pig.data.Tuple inputTuple)
                throws IOException

An Accumulator version of the standard exec() method. Like exec(), accumulator is called with a bag of Datum Tuples. Unlike exec(), it doesn't serialize the result at the end. Instead, it can be called multiple times, each time with another bag of Datum Tuples to be input to the sketch.

Specified by:

accumulate in interface org.apache.pig.Accumulator<org.apache.pig.data.DataByteArray>

Parameters:

inputTuple - A tuple containing a single bag, containing Datum Tuples.

Throws:

IOException - by Pig

See Also:

exec(org.apache.pig.data.Tuple), "org.apache.pig.Accumulator.accumulate(org.apache.pig.data.Tuple)"

getValue

public org.apache.pig.data.DataByteArray getValue()

Returns the sketch that has been built up by multiple calls to accumulate(org.apache.pig.data.Tuple).

Specified by:

getValue in interface org.apache.pig.Accumulator<org.apache.pig.data.DataByteArray>

Returns:

serialized CpcSketch

See Also:

"org.apache.pig.Accumulator.getValue()"

cleanup

public void cleanup()

Cleans up the UDF state after being called using the Accumulator interface.

Specified by:

cleanup in interface org.apache.pig.Accumulator<org.apache.pig.data.DataByteArray>

See Also:

"org.apache.pig.Accumulator.cleanup()"

getInitial

public String getInitial()

Specified by:

getInitial in interface org.apache.pig.Algebraic

getIntermed

public String getIntermed()

Specified by:

getIntermed in interface org.apache.pig.Algebraic

getFinal

public String getFinal()

Specified by:

getFinal in interface org.apache.pig.Algebraic