org.terrier.structures.postings

Class ORIterablePosting

java.lang.Object

org.terrier.structures.postings.IterablePostingImpl

org.terrier.structures.postings.ORIterablePosting

All Implemented Interfaces:

Closeable, AutoCloseable, IterablePosting, Posting

Direct Known Subclasses:

BlockORIterablePosting, FieldORIterablePosting

public class ORIterablePosting
extends IterablePostingImpl

An IterablePosting that combines more than one IterablePosting into a single IterablePosting. By doing so, multiple term's posting lists can appear as a singe posting list.

Since:

3.5

Author:

Craig Macdonald

See Also:

FieldORIterablePosting, BlockORIterablePosting, BlockFieldORIterablePosting

Field Summary

Fields inherited from interface org.terrier.structures.postings.IterablePosting

END_OF_LIST, EOL

Constructor Summary

Constructors

Constructor and Description
ORIterablePosting(IterablePosting[] ips) Create a Basic ORIterablePosting from the specified postings

Method Summary

Modifier and Type	Method and Description
protected void	addPosting(Posting p)
WritablePosting	asWritablePosting() Copies this posting to one free of an iterator.
void	close()
boolean	endOfPostings() Status method to see if this posting list iterator has been finished
protected void	firstPosting(Posting p)
int	getDocumentLength() Return the length of the document for this posting.
int	getFrequency() Return the frequency of the term in the current document
int	getId() Return the id of the current posting.
static ORIterablePosting	mergePostings(IterablePosting[] ips) Factory method to create an appropriate ORIterablePosting from the specified IterablePostings.
int	next() Move this iterator to the next posting.
int	next(int target) This implementation of next(int) which uses next()
void	setId(int _id) It may be of benefit to update the frequency of the id in some applications.

Methods inherited from class java.lang.Object

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

Constructor Detail

ORIterablePosting

public ORIterablePosting(IterablePosting[] ips)
                  throws IOException

Create a Basic ORIterablePosting from the specified postings

Throws:

IOException

Method Detail

mergePostings

public static ORIterablePosting mergePostings(IterablePosting[] ips)
                                       throws IOException

Factory method to create an appropriate ORIterablePosting from the specified IterablePostings. Four types of ORIterablePosting maybe returned, based on the lowest common denominator type of the specified IterablePosting classes:

• BlockFieldORIterablePosting - if the all posting lists are both a BlockPosting and FieldPosting
• BlockORIterablePosting - if the all posting lists are a BlockPosting but not all a FieldPosting
• FieldORIterablePosting - if the all posting lists are a FieldPosting but not all a BlockPosing
• ORIterablePosting - otherwise

Throws:

IOException

endOfPostings

public boolean endOfPostings()

Status method to see if this posting list iterator has been finished

Returns:

true if next() or next(int) would return EOL or have returned EOL.

firstPosting

protected void firstPosting(Posting p)

addPosting

protected void addPosting(Posting p)

next

public int next()
         throws IOException

Move this iterator to the next posting.

Returns:

id of next posting, or EOL if end of posting list

Throws:

IOException

next

public int next(int target)
         throws IOException

Description copied from class: IterablePostingImpl

This implementation of next(int) which uses next()

Specified by:

next in interface IterablePosting

Overrides:

next in class IterablePostingImpl

Parameters:

target - id of the posting to find in this posting list.

Returns:

id of the posting found, or EOL if end of posting list.

Throws:

IOException

asWritablePosting

public WritablePosting asWritablePosting()

Copies this posting to one free of an iterator. Kind of like a clone.

Returns:

an identical posting, but which can be maniulated free of this iterator

getDocumentLength

public int getDocumentLength()

Return the length of the document for this posting. Usually uses the DocumentIndex, may do otherwise if document length statistics are in posting list

Returns:

length of the document of the current posting in tokens.

getFrequency

public int getFrequency()

Return the frequency of the term in the current document

Returns:

frequency of posting, in tokens

getId

public int getId()

Return the id of the current posting. For the inverted index, this is the docid; for the direct index it corresponds to the term id

Returns:

id of the posting

setId

public void setId(int _id)

It may be of benefit to update the frequency of the id in some applications. This should not be used lightly, as it may break the decompression of other postings in iterators.

close

public void close()
           throws IOException

Throws:

IOException