org.terrier.realtime.multi

Class MultiDirectIterablePosting

java.lang.Object

org.terrier.realtime.multi.MultiDirectIterablePosting

All Implemented Interfaces:

Closeable, AutoCloseable, IterablePosting, Posting

Direct Known Subclasses:

BlockMultiDirectIterablePosting

public class MultiDirectIterablePosting
extends Object
implements IterablePosting

This acts as a wrapper class that surrounds an IterablePosting object. It is designed for use with the MultiDirect structure, to allow fast termid lookups. The motivation is that when iterating over a direct index, the termids that come out are index shard local. To fix this, we add on the number of terms in each preceding lexicon to turn local termids into global ones. The MultiLexicon is then responsible for converting the global termid into its local termid and index shard components, which can be used to do the termid lookup.

Since:

4.0

Author:

Richard McCreadie

Field Summary

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

END_OF_LIST, EOL

Constructor Summary

Constructors

Constructor and Description
MultiDirectIterablePosting(IterablePosting posting, MultiLexicon lex, int shard)

Method Summary

Modifier and Type	Method and Description
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
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.
int	next() Move this iterator to the next posting.
int	next(int targetId) Move this iterator to the posting with specified id, or next posting after that.
static MultiDirectIterablePosting	of(IterablePosting ip, MultiLexicon lex, int shard, boolean blocks, boolean fields)
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

MultiDirectIterablePosting

public MultiDirectIterablePosting(IterablePosting posting,
                                  MultiLexicon lex,
                                  int shard)

Method Detail

getId

public int getId()

Description copied from interface: Posting

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

Specified by:

getId in interface Posting

Returns:

id of the posting

getFrequency

public int getFrequency()

Description copied from interface: Posting

Return the frequency of the term in the current document

Specified by:

getFrequency in interface Posting

Returns:

frequency of posting, in tokens

getDocumentLength

public int getDocumentLength()

Description copied from interface: Posting

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

Specified by:

getDocumentLength in interface Posting

Returns:

length of the document of the current posting in tokens.

setId

public void setId(int id)

Description copied from interface: Posting

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.

Specified by:

setId in interface Posting

asWritablePosting

public WritablePosting asWritablePosting()

Description copied from interface: Posting

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

Specified by:

asWritablePosting in interface Posting

Returns:

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

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

next

public int next()
         throws IOException

Description copied from interface: IterablePosting

Move this iterator to the next posting.

Specified by:

next in interface IterablePosting

Returns:

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

Throws:

IOException

next

public int next(int targetId)
         throws IOException

Description copied from interface: IterablePosting

Move this iterator to the posting with specified id, or next posting after that. This is usually implemented internally by next(), but more efficient implementations can override this behaviour.

Specified by:

next in interface IterablePosting

Parameters:

targetId - 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

endOfPostings

public boolean endOfPostings()

Description copied from interface: IterablePosting

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

Specified by:

endOfPostings in interface IterablePosting

Returns:

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

of

public static MultiDirectIterablePosting of(IterablePosting ip,
                                            MultiLexicon lex,
                                            int shard,
                                            boolean blocks,
                                            boolean fields)