## org.apache.hadoop.util.bloom
Class RetouchedBloomFilter

    java.lang.Object
      org.apache.hadoop.util.bloom.Filter
          org.apache.hadoop.util.bloom.BloomFilter
              org.apache.hadoop.util.bloom.RetouchedBloomFilter

All Implemented Interfaces:
  Writable, RemoveScheme

    public final class RetouchedBloomFilter

extends BloomFilter
implements RemoveScheme

Implements a retouched Bloom filter, as defined in the CoNEXT 2006 paper.

It allows the removal of selected false positives at the cost of introducing random false negatives, and with the benefit of eliminating some random false positives at the same time.

Originally created by European Commission One-Lab Project 034819.

See Also:
  `The general behavior of a filter`, `A Bloom filter`, `The different selective clearing algorithms`, Retouched Bloom Filters: Allowing Networked Applications to Trade Off Selected False Positives Against False Negatives

Field Summary

Fields inherited from class org.apache.hadoop.util.bloom.Filter
`hash, hashType, nbHash, vectorSize`

Fields inherited from interface org.apache.hadoop.util.bloom.RemoveScheme
`MAXIMUM_FP, MINIMUM_FN, RANDOM, RATIO`

Constructor Summary
`RetouchedBloomFilter()` Default constructor - use with readFields
`RetouchedBloomFilter(int vectorSize, int nbHash, int hashType)` Constructor

Method Summary
`void` `add(Key key)` Adds a key to this filter.
`void` `addFalsePositive(Collection<Key> coll)` Adds a collection of false positive information to this retouched Bloom filter.
`void` `addFalsePositive(Key key)` Adds a false positive information to this retouched Bloom filter.
`void` `addFalsePositive(Key[] keys)` Adds an array of false positive information to this retouched Bloom filter.
`void` `addFalsePositive(List<Key> keys)` Adds a list of false positive information to this retouched Bloom filter.
`void` `readFields(DataInput in)` Deserialize the fields of this object from `in`.
`void` `selectiveClearing(Key k, short scheme)` Performs the selective clearing for a given key.
`void` `write(DataOutput out)` Serialize the fields of this object to `out`.

Methods inherited from class org.apache.hadoop.util.bloom.BloomFilter
`and, getVectorSize, membershipTest, not, or, toString, xor`

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

### RetouchedBloomFilter

    public RetouchedBloomFilter()

  Default constructor - use with readFields

### RetouchedBloomFilter

    public RetouchedBloomFilter(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(Key key)

  Description copied from class: `Filter`
  Adds a key to this filter.

  Overrides:
    `add` in class `BloomFilter`
  Parameters:
    `key` - The key to add.

### addFalsePositive

    public void addFalsePositive(Key key)

  Adds a false positive information to this retouched Bloom filter.

  Invariant: if the false positive is `null`, nothing happens.

  Parameters:
    `key` - The false positive key to add.

### addFalsePositive

    public void addFalsePositive(Collection<Key> coll)

  Adds a collection of false positive information to this retouched Bloom filter.

  Parameters:
    `coll` - The collection of false positive.

### addFalsePositive

    public void addFalsePositive(List<Key> keys)

  Adds a list of false positive information to this retouched Bloom filter.

  Parameters:
    `keys` - The list of false positive.

### addFalsePositive

    public void addFalsePositive(Key[] keys)

  Adds an array of false positive information to this retouched Bloom filter.

  Parameters:
    `keys` - The array of false positive.

### selectiveClearing

    public void selectiveClearing(Key k,
                                  short scheme)

  Performs the selective clearing for a given key.

  Parameters:
    `k` - The false positive key to remove from this retouched Bloom filter.
    `scheme` - The selective clearing scheme to apply.

### write

    public void write(DataOutput out)
               throws IOException

  Description copied from interface: `Writable`
  Serialize the fields of this object to `out`.

  Specified by:
    `write` in interface `Writable`
  Overrides:
    `write` in class `BloomFilter`
  Parameters:
    `out` - `DataOuput` to serialize this object into.
  Throws:
    `IOException`

### readFields

    public void readFields(DataInput in)
                    throws IOException

  Description copied from interface: `Writable`
  Deserialize the fields of this object from `in`.

  For efficiency, implementations should attempt to re-use storage in the existing object where possible.

  Specified by:
    `readFields` in interface `Writable`
  Overrides:
    `readFields` in class `BloomFilter`
  Parameters:
    `in` - `DataInput` to deseriablize this object from.
  Throws:
    `IOException`

Copyright © 2009 The Apache Software Foundation