brickhouse.udf.bloom
Class BloomFilter

java.lang.Object
  org.apache.hadoop.util.bloom.Filter
      brickhouse.udf.bloom.BloomFilter

All Implemented Interfaces:

org.apache.hadoop.io.Writable

public class BloomFilter
extends org.apache.hadoop.util.bloom.Filter

Implements a Bloom filter, as defined by Bloom in 1970.

The Bloom filter is a data structure that was introduced in 1970 and that has been adopted by the networking research community in the past decade thanks to the bandwidth efficiencies that it offers for the transmission of set membership information between networked hosts. A sender encodes the information into a bit vector, the Bloom filter, that is more compact than a conventional representation. Computation and space costs for construction are linear in the number of elements. The receiver uses the filter to test whether various elements are members of the set. Though the filter will occasionally return a false positive, it will never return a false negative. When creating the filter, the sender can choose its desired point in a trade-off between the false positive rate and the size.

Originally created by European Commission One-Lab Project 034819.

See Also:

The general behavior of a filter, Space/Time Trade-Offs in Hash Coding with Allowable Errors

Field Summary

Fields inherited from class org.apache.hadoop.util.bloom.Filter

hash, hashType, nbHash, vectorSize

Constructor Summary

BloomFilter()
Default constructor - use with readFields

BloomFilter(int vectorSize, int nbHash, int hashType)
Constructor

Method Summary

void	add(org.apache.hadoop.util.bloom.Key key)
void	and(org.apache.hadoop.util.bloom.Filter filter)
int	getVectorSize()
boolean	membershipTest(org.apache.hadoop.util.bloom.Key key)
void	not()
void	or(org.apache.hadoop.util.bloom.Filter filter)
void	readFields(DataInput in)
String	toString()
void	write(DataOutput out)
void	xor(org.apache.hadoop.util.bloom.Filter filter)

Methods inherited from class org.apache.hadoop.util.bloom.Filter

add, add, add

Methods inherited from class java.lang.Object

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

Constructor Detail

BloomFilter

public BloomFilter()

Default constructor - use with readFields

BloomFilter

public BloomFilter(int vectorSize,
                   int nbHash,
                   int hashType)

Constructor

Parameters:

vectorSize - The vector size of this filter.

nbHash - The number of hash function to consider.

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

Method Detail

add

public void add(org.apache.hadoop.util.bloom.Key key)

Specified by:

add in class org.apache.hadoop.util.bloom.Filter

and

public void and(org.apache.hadoop.util.bloom.Filter filter)

Specified by:

and in class org.apache.hadoop.util.bloom.Filter

membershipTest

public boolean membershipTest(org.apache.hadoop.util.bloom.Key key)

Specified by:

membershipTest in class org.apache.hadoop.util.bloom.Filter

not

public void not()

Specified by:

not in class org.apache.hadoop.util.bloom.Filter

or

public void or(org.apache.hadoop.util.bloom.Filter filter)

Specified by:

or in class org.apache.hadoop.util.bloom.Filter

xor

public void xor(org.apache.hadoop.util.bloom.Filter filter)

Specified by:

xor in class org.apache.hadoop.util.bloom.Filter

toString

public String toString()

Overrides:

toString in class Object

getVectorSize

public int getVectorSize()

Returns:

size of the the bloomfilter

write

public void write(DataOutput out)
           throws IOException

Specified by:

write in interface org.apache.hadoop.io.Writable

Overrides:

write in class org.apache.hadoop.util.bloom.Filter

Throws:

IOException

readFields

public void readFields(DataInput in)
                throws IOException

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Overrides:

readFields in class org.apache.hadoop.util.bloom.Filter

Throws:

IOException