org.apache.lucene.util.packed

Class EliasFanoDocIdSet

java.lang.Object

org.apache.lucene.search.DocIdSet

org.apache.lucene.util.packed.EliasFanoDocIdSet

All Implemented Interfaces:

Accountable

public class EliasFanoDocIdSet
extends DocIdSet

A DocIdSet in Elias-Fano encoding.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Field Summary

Fields inherited from class org.apache.lucene.search.DocIdSet

EMPTY

Constructor Summary

Constructors

Constructor and Description
EliasFanoDocIdSet(int numValues, int upperBound) Construct an EliasFanoDocIdSet.

Method Summary

Methods

Modifier and Type	Method and Description
void	encodeFromDisi(DocIdSetIterator disi) Encode the document ids from a DocIdSetIterator.
boolean	equals(Object other)
int	hashCode()
boolean	isCacheable() This DocIdSet implementation is cacheable.
DocIdSetIterator	iterator() Provides a DocIdSetIterator to access encoded document ids.
long	ramBytesUsed() Return the memory usage of this object in bytes.
static boolean	sufficientlySmallerThanBitSet(long numValues, long upperBound) Provide an indication that is better to use an EliasFanoDocIdSet than a FixedBitSet to encode document identifiers.

Methods inherited from class org.apache.lucene.search.DocIdSet

bits

Methods inherited from class java.lang.Object

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

Constructor Detail

EliasFanoDocIdSet

public EliasFanoDocIdSet(int numValues,
                 int upperBound)

Construct an EliasFanoDocIdSet. For efficient encoding, the parameters should be chosen as low as possible.

Parameters:

numValues - At least the number of document ids that will be encoded.

upperBound - At least the highest document id that will be encoded.

Method Detail

sufficientlySmallerThanBitSet

public static boolean sufficientlySmallerThanBitSet(long numValues,
                                    long upperBound)

Provide an indication that is better to use an EliasFanoDocIdSet than a FixedBitSet to encode document identifiers.

Parameters:

numValues - The number of document identifiers that is to be encoded. Should be non negative.

upperBound - The maximum possible value for a document identifier. Should be at least numValues.

Returns:

See EliasFanoEncoder.sufficientlySmallerThanBitSet(long, long)

encodeFromDisi

public void encodeFromDisi(DocIdSetIterator disi)
                    throws IOException

Encode the document ids from a DocIdSetIterator.

Parameters:

disi - This DocIdSetIterator should provide document ids that are consistent with numValues and upperBound as provided to the constructor.

Throws:

IOException

iterator

public DocIdSetIterator iterator()

Provides a DocIdSetIterator to access encoded document ids.

Specified by:

iterator in class DocIdSet

isCacheable

public boolean isCacheable()

This DocIdSet implementation is cacheable.

Overrides:

isCacheable in class DocIdSet

Returns:

true

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

ramBytesUsed

public long ramBytesUsed()

Description copied from interface: Accountable

Return the memory usage of this object in bytes. Negative values are illegal.

Specified by:

ramBytesUsed in interface Accountable

Overrides:

ramBytesUsed in class DocIdSet