ivory.ffg.data

Class CompressedPositionalPostings

java.lang.Object

ivory.bloomir.data.CompressedPostings

ivory.ffg.data.CompressedPositionalPostings

All Implemented Interfaces:

Writable

public class CompressedPositionalPostings
extends CompressedPostings

A compressed positional postings list representation. This class uses PForDelta to compress a given set of document ids into blocks of equal size. In this implementation, the positions are compressed using gamma coding.

Author:

Nima Asadi

Method Summary

Methods

Modifier and Type	Method and Description
void	close()
int[]	decompressPositions(int index) Retrieves positions for a document given a forward index and the index of the document in the document id vector.
boolean	equals(Object o)
static CompressedPositionalPostings	newInstance(int[] data, List<TermPositions> positions) Constructs an instance of this class by encoding the document ids as well as their term positions
void	readFields(DataInput input)
static CompressedPositionalPostings	readInstance(DataInput input) Reads and returns an instance of this class from input
void	write(DataOutput output)

Methods inherited from class ivory.bloomir.data.CompressedPostings

decompressBlock, getBlockCount, getBlockNumber, getBlockSize, getBlockStartIndex, getPositionInBlock, isFirstElementInBlock, newInstance

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

close

public void close()

decompressPositions

public int[] decompressPositions(int index)
                          throws IOException

Retrieves positions for a document given a forward index and the index of the document in the document id vector.

Parameters:

index - Index of the document id in the document id vector

Returns:

Positions of the occurrences of the term within a document

Throws:

IOException

equals

public boolean equals(Object o)

Overrides:

equals in class CompressedPostings

newInstance

public static CompressedPositionalPostings newInstance(int[] data,
                                       List<TermPositions> positions)
                                                throws IOException

Constructs an instance of this class by encoding the document ids as well as their term positions

Parameters:

data - An array of document ids

positions - List of TermPosition objects, one for each document id

Returns:

A compressed positional postings list object

Throws:

IOException

readFields

public void readFields(DataInput input)
                throws IOException

Specified by:

readFields in interface Writable

Overrides:

readFields in class CompressedPostings

Throws:

IOException

readInstance

public static CompressedPositionalPostings readInstance(DataInput input)
                                                 throws IOException

Reads and returns an instance of this class from input

Parameters:

input - DataInput

Returns:

An instance of the compressed positional postings list

Throws:

IOException

write

public void write(DataOutput output)
           throws IOException

Specified by:

write in interface Writable

Overrides:

write in class CompressedPostings

Throws:

IOException