How to implement a new backend

Index

• Subclass :class:` whoosh.index.Index`.

• Indexes must implement the following methods.

  • :meth:` whoosh.index.Index.is_empty`

  • :meth:` whoosh.index.Index.doc_count`

  • :meth:` whoosh.index.Index.reader`

  • :meth:` whoosh.index.Index.writer`

• Indexes that require/support locking must implement the following methods.

  • :meth:` whoosh.index.Index.lock`

  • :meth:` whoosh.index.Index.unlock`

• Indexes that support deletion must implement the following methods.

  • :meth:` whoosh.index.Index.delete_document`

  • :meth:` whoosh.index.Index.doc_count_all` – if the backend has delayed deletion.

• Indexes that require/support versioning/transactions may implement the following methods.

  • :meth:` whoosh.index.Index.latest_generation`

  • :meth:` whoosh.index.Index.up_to_date`

  • :meth:` whoosh.index.Index.last_modified`

• Index may implement the following methods (the base class’s versions are no-ops).

  • :meth:` whoosh.index.Index.optimize`

  • :meth:` whoosh.index.Index.close`

IndexWriter

• Subclass :class:` whoosh.writing.IndexWriter`.

• IndexWriters must implement the following methods.

  • :meth:` whoosh.writing.IndexWriter.add_document`

  • :meth:` whoosh.writing.IndexWriter.add_reader`

• Backends that support deletion must implement the following methods.

  • :meth:` whoosh.writing.IndexWriter.delete_document`

• IndexWriters that work as transactions must implement the following methods.

  • :meth:` whoosh.reading.IndexWriter.commit` – Save the additions/deletions done with this IndexWriter to the main index, and release any resources used by the IndexWriter.

  • :meth:` whoosh.reading.IndexWriter.cancel` – Throw away any additions/deletions done with this IndexWriter, and release any resources used by the IndexWriter.

IndexReader

• Subclass :class:` whoosh.reading.IndexReader`.

• IndexReaders must implement the following methods.

  • :meth:` whoosh.reading.IndexReader.__contains__`

  • :meth:` whoosh.reading.IndexReader.__iter__`

  • :meth:` whoosh.reading.IndexReader.iter_from`

  • :meth:` whoosh.reading.IndexReader.stored_fields`

  • :meth:` whoosh.reading.IndexReader.doc_count_all`

  • :meth:` whoosh.reading.IndexReader.doc_count`

  • :meth:` whoosh.reading.IndexReader.doc_field_length`

  • :meth:` whoosh.reading.IndexReader.field_length`

  • :meth:` whoosh.reading.IndexReader.max_field_length`

  • :meth:` whoosh.reading.IndexReader.postings`

  • :meth:` whoosh.reading.IndexReader.has_vector`

  • :meth:` whoosh.reading.IndexReader.vector`

  • :meth:` whoosh.reading.IndexReader.doc_frequency`

  • :meth:` whoosh.reading.IndexReader.frequency`

• Backends that support deleting documents should implement the following methods.

  • :meth:` whoosh.reading.IndexReader.has_deletions`

  • :meth:` whoosh.reading.IndexReader.is_deleted`

• Backends that support versioning should implement the following methods.

  • :meth:` 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.

  • :meth:` whoosh.reading.IndexReader.field`

  • :meth:` whoosh.reading.IndexReader.field_names`

  • :meth:` whoosh.reading.IndexReader.scorable_names`

  • :meth:` whoosh.reading.IndexReader.vector_names`

• IndexReaders may implement the following methods.

  • :meth:` whoosh.reading.DocReader.close` – closes any open resources associated with the reader.

Matcher

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

• Subclass :class:` whoosh.matching.Matcher`.

• Implement the following methods at minimum.

  • :meth:` whoosh.matching.Matcher.is_active`

  • :meth:` whoosh.matching.Matcher.copy`

  • :meth:` whoosh.matching.Matcher.id`

  • :meth:` whoosh.matching.Matcher.next`

  • :meth:` whoosh.matching.Matcher.value`

  • :meth:` whoosh.matching.Matcher.value_as`

  • :meth:` whoosh.matching.Matcher.score`

• Depending on the implementation, you may implement the following methods more efficiently.

  • :meth:` whoosh.matching.Matcher.skip_to`

  • :meth:` whoosh.matching.Matcher.weight`

• If the implementation supports quality, you should implement the following methods.

  • :meth:` whoosh.matching.Matcher.supports_quality`

  • :meth:` whoosh.matching.Matcher.quality`

  • :meth:` whoosh.matching.Matcher.block_quality`

  • :meth:` whoosh.matching.Matcher.skip_to_quality`