Package org.terrier.structures.postings

Provides classes representing single postings and atreams of postings in a posting list (e.g. an inverted index or a direct index).

A single posting (e.g. occurrences of a term in document) is represented by a Posting object.

Posting p;
System.out.println("Docid "+ p.getId() + " has " + p.getFrequency() + " occurrences");

A stream of postings (e.g. terms in a document or occurrences of a term) are represented by an IterablePosting stream.

IterablePosting ip = //obtain from InvertedIndex;
while(ip.next() != IterablePosting.EOL)
{
  System.err.println("Docid "+ ip.getId() + " has " + ip.getFrequency() + " occurrences");
}

More complex posting implementations are supported by other Posting child interfaces:

• Posting - basic posting: id, frequency and document length only.
• BlockPosting - positions of occurrences are available.
• FieldPosting - the frequencies in each field, as well as field lengths are available.

In all cases during retrieval, IterablePosting implementations which also implement Posting, BlockPosting and/or FieldPosting are used, depending on how indexing has been performed. To see how to configure indexing, see Configure Indexing.

Interface Summary

Interface	Description
BlockPosting	Interface implemented by posting objects that have position information recorded.
FieldPosting	Interface implemented by posting objects that have field information recorded.
IterablePosting	An interface that allows a list of postings to be iterated over.
Posting	This interface represents one posting in a posting list.
WritablePosting	Allow a Posting to be serialized to a DataOut.

Class Summary

Class	Description
ANDIterablePosting	An instance of IterablePostings that works with passed arrays of ids and frequencies.
ArrayOfBasicIterablePosting	An instance of IterablePostings that works with passed arrays of ids and frequencies
ArrayOfBlockFieldIterablePosting	An array structure that golds BlockFieldIterablePostings
ArrayOfBlockIterablePosting	An array structure that golds BlockIterablePostings
ArrayOfFieldIterablePosting	An instance of IterablePostings that works with passed arrays of ids and frequencies for each field.
ArrayOfIdsIterablePosting	An instance of IterablePostings that works with a passed array of ids
BasicPostingImpl	Implementation of a Posting that is non-iterable.
BlockFieldORIterablePosting	ORIterablePosting implementation that implements FieldPosting and BlockPosting
BlockFieldPostingImpl	A writable block field posting list
BlockORIterablePosting	ORIterablePosting implementation that implements BlockPosting
BlockPostingImpl	BlockPostingImpl class
FieldOnlyIterablePosting	This class takes an IterablePosting list that has fields, and makes it appear as a single basic posting list.
FieldORIterablePosting	ORIterablePosting implementation that implements FieldPosting
FieldPostingImpl	Implementation of a posting containing fields
IterablePostingImpl	A base implementation of an IterablePosting, that provides a base implementation of next(int) method.
ORIterablePosting	An IterablePosting that combines more than one IterablePosting into a single IterablePosting.
PhraseIterablePosting	Implementation of an IterablePosting for block indices that returns only documents that match a multi-term phase.
PostingIdComparator	A comparator object for Posting objects, where they are sorted by id.
PostingTestUtils
PostingUtil	Handy methods for Posting classes, such as obtaining all ids in a posting list, or selecting the minimum id in an array of posting lists.
PostingUtil.DocidSpecificDocumentIndex
ProximityIterablePosting	Implementation of an IterablePosting for block indices that returns only documents that match phases within a fixed window size.