How to implement a new backend

Index

• Subclass whoosh.index.Index.
• Indexes must implement the following methods.
  • whoosh.index.Index.is_empty()
  • whoosh.index.Index.doc_count()
  • whoosh.index.Index.reader()
  • whoosh.index.Index.writer()
• Indexes that require/support locking must implement the following methods.
  • whoosh.index.Index.lock()
  • whoosh.index.Index.unlock()
• Indexes that support deletion must implement the following methods.
  • whoosh.index.Index.delete_document()
  • whoosh.index.Index.doc_count_all() – if the backend has delayed deletion.
• Indexes that require/support versioning/transactions may implement the following methods.
  • whoosh.index.Index.latest_generation()
  • whoosh.index.Index.up_to_date()
  • whoosh.index.Index.last_modified()
• Index may implement the following methods (the base class’s versions are no-ops).
  • whoosh.index.Index.optimize()
  • whoosh.index.Index.close()

IndexWriter

• Subclass whoosh.writing.IndexWriter.
• IndexWriters must implement the following methods.
  • whoosh.writing.IndexWriter.add_document()
  • whoosh.writing.IndexWriter.add_reader()
• Backends that support deletion must implement the following methods.
  • whoosh.writing.IndexWriter.delete_document()
• IndexWriters that work as transactions must implement the following methods.
  • whoosh.reading.IndexWriter.commit() – Save the additions/deletions done with this IndexWriter to the main index, and release any resources used by the IndexWriter.
  • whoosh.reading.IndexWriter.cancel() – Throw away any additions/deletions done with this IndexWriter, and release any resources used by the IndexWriter.

IndexReader

• Subclass whoosh.reading.IndexReader.
• IndexReaders must implement the following methods.
  • whoosh.reading.IndexReader.__contains__()
  • whoosh.reading.IndexReader.__iter__()
  • whoosh.reading.IndexReader.iter_from()
  • whoosh.reading.IndexReader.stored_fields()
  • whoosh.reading.IndexReader.doc_count_all()
  • whoosh.reading.IndexReader.doc_count()
  • whoosh.reading.IndexReader.doc_field_length()
  • whoosh.reading.IndexReader.field_length()
  • whoosh.reading.IndexReader.max_field_length()
  • whoosh.reading.IndexReader.postings()
  • whoosh.reading.IndexReader.has_vector()
  • whoosh.reading.IndexReader.vector()
  • whoosh.reading.IndexReader.doc_frequency()
  • whoosh.reading.IndexReader.frequency()
• Backends that support deleting documents should implement the following methods.
  • whoosh.reading.IndexReader.has_deletions()
  • whoosh.reading.IndexReader.is_deleted()
• Backends that support versioning should implement the following methods.
  • whoosh.reading.IndexReader.generation()
• If the IndexReader object does not keep the schema in the self.schema attribute, it needs to override the following methods.
  • whoosh.reading.IndexReader.field()
  • whoosh.reading.IndexReader.field_names()
  • whoosh.reading.IndexReader.scorable_names()
  • whoosh.reading.IndexReader.vector_names()
• IndexReaders may implement the following methods.
  • whoosh.reading.DocReader.close() – closes any open resources associated with the reader.

Matcher

The whoosh.reading.IndexReader.postings() method returns a whoosh.matching.Matcher object. You will probably need to implement a custom Matcher class for reading from your posting lists.

• Subclass whoosh.matching.Matcher.
• Implement the following methods at minimum.
  • whoosh.matching.Matcher.is_active()
  • whoosh.matching.Matcher.copy()
  • whoosh.matching.Matcher.id()
  • whoosh.matching.Matcher.next()
  • whoosh.matching.Matcher.value()
  • whoosh.matching.Matcher.value_as()
  • whoosh.matching.Matcher.score()
• Depending on the implementation, you may implement the following methods more efficiently.
  • whoosh.matching.Matcher.skip_to()
  • whoosh.matching.Matcher.weight()
• If the implementation supports quality, you should implement the following methods.
  • whoosh.matching.Matcher.supports_quality()
  • whoosh.matching.Matcher.quality()
  • whoosh.matching.Matcher.block_quality()
  • whoosh.matching.Matcher.skip_to_quality()