org.terrier.structures.postings.bit

Class BasicIterablePosting

java.lang.Object

org.terrier.structures.postings.BasicPostingImpl

org.terrier.structures.postings.bit.BasicIterablePosting

All Implemented Interfaces:

Closeable, Serializable, AutoCloseable, org.apache.hadoop.io.Writable, IterablePosting, Posting, WritablePosting

Direct Known Subclasses:

BasicIterablePostingDocidOnly, BlockFieldIterablePosting, BlockIterablePosting, FieldIterablePosting

public class BasicIterablePosting
extends BasicPostingImpl
implements IterablePosting

Basic inverted and direct index format: [gamma(first docid +1) unary (frequency)], [gamma(delta docid) unary(frequency)]

Since:

3.0

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected BitIn	bitFileReader
protected DocumentIndex	doi
protected int	numEntries

Fields inherited from class org.terrier.structures.postings.BasicPostingImpl

dl, id, tf

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

EOL

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BasicIterablePosting() Create a new posting iterator
	BasicIterablePosting(BitIn _bitFileReader, int _numEntries, DocumentIndex _doi) Create a new posting iterator

Method Summary

Methods

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() Returns 0
int	next() Move this iterator to the next posting.
int	next(int target) Move this iterator to the posting with specified id, or next posting after that.

Methods inherited from class org.terrier.structures.postings.BasicPostingImpl

getFrequency, getId, readFields, setDocumentLength, setId, setTf, toString, write

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.terrier.structures.postings.Posting

getFrequency, getId, setId

Field Detail

numEntries

protected int numEntries

bitFileReader

protected BitIn bitFileReader

doi

protected DocumentIndex doi

Constructor Detail

BasicIterablePosting

protected BasicIterablePosting()

Create a new posting iterator

BasicIterablePosting

public BasicIterablePosting(BitIn _bitFileReader,
                    int _numEntries,
                    DocumentIndex _doi)
                     throws IOException

Create a new posting iterator

Parameters:

_bitFileReader - BitIn to read the postings from

_numEntries - number of postings in the list

_doi - document index to use to satisfy getDocumentLength()

Throws:

IOException - thrown in an IO exception occurs

Method Detail

next

public int next()
         throws IOException

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 target)
         throws IOException

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

Specified by:

next in interface IterablePosting

Parameters:

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

Returns:

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

Throws:

IOException

endOfPostings

public boolean endOfPostings()

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.

getDocumentLength

public int getDocumentLength()

Returns 0

Specified by:

getDocumentLength in interface Posting

Overrides:

getDocumentLength in class BasicPostingImpl

Returns:

length of the document of the current posting in tokens.

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

asWritablePosting

public WritablePosting asWritablePosting()

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

Specified by:

asWritablePosting in interface Posting

Overrides:

asWritablePosting in class BasicPostingImpl

Returns:

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