org.apache.pig.builtin
Class BuildBloom

java.lang.Object
  org.apache.pig.EvalFunc<T>
      org.apache.pig.builtin.BuildBloomBase<DataByteArray>
          org.apache.pig.builtin.BuildBloom

All Implemented Interfaces:

Algebraic

public class BuildBloom
extends BuildBloomBase<DataByteArray>
implements Algebraic

Build a bloom filter for use later in Bloom. This UDF is intended to run in a group all job. For example: define bb BuildBloom('jenkins', '100', '0.1'); A = load 'foo' as (x, y); B = group A all; C = foreach B generate BuildBloom(A.x); store C into 'mybloom'; The bloom filter can be on multiple keys by passing more than one field (or the entire bag) to BuildBloom. The resulting file can then be used in a Bloom filter as: define bloom Bloom(mybloom); A = load 'foo' as (x, y); B = load 'bar' as (z); C = filter B by Bloom(z); D = join C by z, A by x; It uses BloomFilter.

Nested Class Summary

static class	BuildBloom.Final
static class	BuildBloom.Initial
static class	BuildBloom.Intermediate

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

EvalFunc.SchemaType

Field Summary

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

filter, hType, numHash, vSize

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

BuildBloom(String hashType, String numElements, String desiredFalsePositive)
Construct a Bloom filter based on expected number of elements and desired accuracy.

BuildBloom(String hashType, String mode, String vectorSize, String nbHash)
Build a bloom filter of fixed size and number of hash functions.

Method Summary

DataByteArray	exec(Tuple input) This callback method must be implemented by all subclasses.
String	getFinal() Get the final function.
String	getInitial() Get the initial function.
String	getIntermed() Get the intermediate function.
Schema	outputSchema(Schema input) Report the schema of the output of this UDF.

Methods inherited from class org.apache.pig.builtin.BuildBloomBase

bloomIn, bloomOr, bloomOut

Methods inherited from class org.apache.pig.EvalFunc

finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, isAsynchronous, progress, 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

BuildBloom

public BuildBloom(String hashType,
                  String mode,
                  String vectorSize,
                  String nbHash)

Build a bloom filter of fixed size and number of hash functions.

Parameters:

hashType - type of the hashing function (see Hash).

mode - Will be ignored, though by convention it should be "fixed" or "fixedsize"

vectorSize - The vector size of this filter.

nbHash - The number of hash functions to consider.

BuildBloom

public BuildBloom(String hashType,
                  String numElements,
                  String desiredFalsePositive)

Construct a Bloom filter based on expected number of elements and desired accuracy.

Parameters:

hashType - type of the hashing function (see Hash).

numElements - The number of distinct elements expected to be placed in this filter.

desiredFalsePositive - the acceptable rate of false positives. This should be a floating point value between 0 and 1.0, where 1.0 would be 100% (ie, a totally useless filter).

Method Detail

exec

public DataByteArray exec(Tuple input)
                   throws IOException

Description copied from class: EvalFunc

This callback method must be implemented by all subclasses. This is the method that will be invoked on every Tuple of a given dataset. Since the dataset may be divided up in a variety of ways the programmer should not make assumptions about state that is maintained between invocations of this method.

Specified by:

exec in class EvalFunc<DataByteArray>

Parameters:

input - the Tuple to be processed.

Returns:

result, of type T.

Throws:

IOException

getInitial

public String getInitial()

Description copied from interface: Algebraic

Get the initial function.

Specified by:

getInitial in interface Algebraic

Returns:

A function name of f_init. f_init should be an eval func. The return type of f_init.exec() has to be Tuple

getIntermed

public String getIntermed()

Description copied from interface: Algebraic

Get the intermediate function.

Specified by:

getIntermed in interface Algebraic

Returns:

A function name of f_intermed. f_intermed should be an eval func. The return type of f_intermed.exec() has to be Tuple

getFinal

public String getFinal()

Description copied from interface: Algebraic

Get the final function.

Specified by:

getFinal in interface Algebraic

Returns:

A function name of f_final. f_final should be an eval func parametrized by the same datum as the eval func implementing this interface.

outputSchema

public Schema outputSchema(Schema input)

Description copied from class: EvalFunc

Report the schema of the output of this UDF. Pig will make use of this in error checking, optimization, and planning. The schema of input data to this UDF is provided.

The default implementation interprets the OutputSchema annotation, if one is present. Otherwise, it returns null (no known output schema).

Overrides:

outputSchema in class EvalFunc<DataByteArray>

Parameters:

input - Schema of the input

Returns:

Schema of the output