Xapian-Haystack -- A backend for Django-Haystack
================================================

Overview
--------
xapian-haystack is a backend for use with the Django Haystack search API and the Xapian search engine.

* More information on Haystack can be found here: `haystacksearch.org <http://haystacksearch.org/>`_.
* More information on Xapian can be found here: `xapian.org <http://xapian.org>`_.

Requirements
------------

- Python 2.4 (May work with 2.3, but untested)
- Django 1.0.x
- Django-Haystack 2.0.X
- Xapian 1.0.13+ (May work with earlier versions, but untested)

Notes
-----

- Due to an issue with mod_python possibly causing deadlocks with Xapian (`issue #364 <http://trac.xapian.org/ticket/364>`_), when Python is not invoked through the "main interpreter", mod_python is not supported with xapian-haystack.  It may work, with some tweaking, but your mileage will vary.

- Because Xapian does not support simultaneous ``WritableDatabase`` connections, it is *strongly* recommended that users take care when using ``RealTimeSearchIndex``.  If there is a possibility of simultaneous write attempts on the database, keep in mind that they are likely to trigger multiple reindex attempts on the search index.  If this occurs an `DatabaseLockError` exception will be raised by Xapian.  To avoid this, either set ``WSGIDaemonProcess processes=1`` or use some other way of ensuring that there are not multiple attempts to write to the indexes.  Alternatively, use ``SearchIndex`` and a cronjob to reindex content at set time intervals (sample cronjob can be found `here <http://gist.github.com/216247>`_) or derive your own ``SearchIndex`` to implement some other form of keeping your indexes up to date.  A good alternative is to use a `QueuedSearchIndex <http://github.com/toastdriven/queued_search>`_.

Installation
------------

#. Copy or symlink ``xapian_backend.py`` into ``haystack/backends/`` or install it by running one of the following commands:

    ``python setup.py install``

    or

    ``pip install xapian-haystack``

    or

    ``easy_install xapian-haystack``

#. Set to something similar to:

    HAYSTACK_CONNECTIONS = {
        'default': {
            'ENGINE': 'haystack.backends.xapian_backend.XapianEngine',
            'PATH': os.path.join(os.path.dirname(__file__), 'xapian_index')
        },
    }

Configuration
-------------

As well as the flags described `here <http://docs.haystacksearch.org/dev/settings.html>`_, the xapian backend includes two additional variables:

    - `HAYSTACK_XAPIAN_FLAGS` -- used to further configure how indexes are stored and manipulated.  By default, this value is set to `FLAG_PHRASE | FLAG_BOOLEAN | FLAG_LOVEHATE | FLAG_WILDCARD | FLAG_PURE_NOT`.  See the `Xapian::QueryParser::feature_flag in the Xapian documentation <http://xapian.org/docs/apidoc/html/classXapian_1_1QueryParser.html>`_ for further explanation of the available Xapian.QueryParser flags.

    - `HAYSTACK_XAPIAN_WEIGHTING_SCHEME` -- used to override the default weighting scheme used during search.  `HAYSTACK_XAPIAN_WEIGHTING_SCHEME` is assumed to be a tuple that corepsonds to the arguments to a BM25Weight constructor.  See `Xapian::BM25Weight::BM25Weight in the Xapian documentation <http://xapian.org/docs/apidoc/html/classXapian_1_1BM25Weight.html>`_ for further information.

    - `HAYSTACK_XAPIAN_LANGUAGE` -- used to override the default stemming language.  By default, Xapian will stem all terms in english.

Testing
-------

The easiest way to test xapian-haystack is to symlink or copy the ``xapian_haystack/tests`` folder into the haystack/tests folder so that your source tree resembles this layout::

    django-haystack
        |
        +---haystack
        |       |
        |       +---backends
        |              |
        |              +---solr_backend.py
        |              +---whoosh_backend.py
        |              +---xapian_backend.py
        +---tests
                |
                +---core
                |    |
                |    +---[...]
                |
                +---[...]
                |
                +---xapian_tests
                |       |
                |       +---[...]
                |
                +---xapian_settings.py

Once this is done, the tests can be executed in a similar fashion as the rest of the Haystack test-suite::

    django-admin.py test xapian_tests --settings=xapian_settings


Source
------

The latest source code can always be found here: `github.com/notanumber/xapian-haystack <http://github.com/notanumber/xapian-haystack/>`_

Credits
-------

xapian-haystack is maintained by `David Sauve <mailto:david.sauve@bag-of-holding.com>`_, and was originally funded by `Trapeze <http://www.trapeze.com>`_.

License
-------

xapian-haystack is Copyright (c) 2009, 2010, 2011, 2012 David Sauve, 2009, 2010 Trapeze. It is free software, and may be redistributed under the terms specified in the LICENSE file.

Questions, Comments, Concerns:
------------------------------

Feel free to open an issue here: `github.com/notanumber/xapian-haystack/issues <http://github.com/notanumber/xapian-haystack/issues>`_
Alternatively, ask questions on the django-haystack `mailing list <http://groups.google.com/group/django-haystack/>`_ or `irc channel <irc://irc.freenode.net/haystack>`_.