org.apache.datasketches.pig.theta

Class DataToSketch

java.lang.Object

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

org.apache.datasketches.pig.theta.DataToSketch

All Implemented Interfaces:

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

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

This is a Pig UDF that builds Sketches from data. To assist Pig, this class implements both the Accumulator and Algebraic interfaces.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DataToSketch.Initial Class used to calculate the initial pass of an Algebraic sketch operation.
static class	DataToSketch.IntermediateFinal Class used to calculate the intermediate or final combiner pass of an Algebraic sketch operation.

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() Default constructor.
DataToSketch(int nomEntries, float p, long seed) Base constructor.
DataToSketch(String nomEntriesStr) String constructor.
DataToSketch(String nomEntriesStr, String pStr) String constructor.
DataToSketch(String nomEntriesStr, String pStr, String seedStr) Full string constructor.

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.Tuple	exec(org.apache.pig.data.Tuple inputTuple) Top-level exec function.
String	getFinal()
String	getInitial()
String	getIntermed()
org.apache.pig.data.Tuple	getValue() Returns the sketch that has been built up by multiple calls to accumulate(org.apache.pig.data.Tuple).
org.apache.pig.impl.logicalLayer.schema.Schema	outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input)

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLoadCaster, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, needEndOfAllInputProcessing, 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()

Default constructor. Assumes:

• See Default Nominal Entries
• p = 1.0. See Sampling Probability, p.
• See Default Update Seed

DataToSketch

public DataToSketch(String nomEntriesStr)

String constructor. Assumes:

• p = 1.0. See Sampling Probability, p
• See Default Update Seed

Parameters:

nomEntriesStr - See Nominal Entries

DataToSketch

public DataToSketch(String nomEntriesStr,
                    String pStr)

String constructor. Assumes:

• See Default Update Seed

Parameters:

nomEntriesStr - See Nominal Entries

pStr - See Sampling Probability, p

DataToSketch

public DataToSketch(String nomEntriesStr,
                    String pStr,
                    String seedStr)

Full string constructor.

Parameters:

nomEntriesStr - See Nominal Entries.

pStr - See Sampling Probability, p.

seedStr - See Update Hash Seed.

DataToSketch

public DataToSketch(int nomEntries,
                    float p,
                    long seed)

Base constructor.

Parameters:

nomEntries - See Nominal Entries.

p - See Sampling Probability, p.

seed - See Update Hash Seed.

Method Detail

exec

public org.apache.pig.data.Tuple 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 updated Sketch as a Sketch Tuple.

If a large number of calls is anticipated, leveraging either the Algebraic or Accumulator interfaces is recommended. Pig normally handles this automatically.

Internally, this method presents the inner Datum Tuples to a new Sketch, which is returned as a Sketch Tuple

Input Tuple

• Tuple: TUPLE (Must contain only one field)
  • index 0: DataBag: BAG (May contain 0 or more Inner Tuples)
    • index 0: Tuple: TUPLE Datum Tuple
    • ...
    • index n-1: Tuple: TUPLE Datum Tuple

Datum Tuple

• Tuple: TUPLE (Must contain only one field)
  • index 0: Java data type : Pig DataType: may be any one of:
    • 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.

Sketch Tuple

• Tuple: TUPLE (Contains exactly 1 field)
  • index 0: DataByteArray: BYTEARRAY = The serialization of a Sketch object.

Specified by:

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

Parameters:

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

Returns:

Sketch Tuple. If inputTuple is null or empty, returns empty sketch (8 bytes).

Throws:

IOException - from Pig.

See Also:

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

outputSchema

public org.apache.pig.impl.logicalLayer.schema.Schema outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input)

Overrides:

outputSchema in class org.apache.pig.EvalFunc<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 sketch 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.Tuple>

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.Tuple 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.Tuple>

Returns:

Sketch Tuple. (see exec(org.apache.pig.data.Tuple) for return tuple format)

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.Tuple>

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