.. _ref-installing-search-engines:

=========================
Installing Search Engines
=========================

Solr
====

Official Download Location: http://www.apache.org/dyn/closer.cgi/lucene/solr/

Solr is Java but comes in a pre=packaged form that requires very little other
than the JRE and Jetty. It's very performant and has an advanced featureset.
Haystack requires Solr 1.3+. Installation is relatively simple::

    curl -O http://apache.mirrors.tds.net/lucene/solr/1.4.1/apache-solr-1.4.1.tgz
    tar xvzf apache-solr-1.4.1.tgz
    cd apache-solr-1.4.1
    cd example
    java -jar start.jar

You'll need to revise your schema. You can generate this from your application
(once Haystack is installed and setup) by running 
``./manage.py build_solr_schema``. Take the output from that command and place
it in ``apache-solr-1.4.1/example/solr/conf/schema.xml``. Then restart Solr.

You'll also need a Solr binding, ``pysolr``. The official ``pysolr`` package,
distributed via PyPI, is the best version to use (2.0.13+). Place ``pysolr.py``
somewhere on your ``PYTHONPATH``.

.. note::

    ``pysolr`` has it's own dependencies that aren't covered by Haystack. For
    best results, you should have an ElementTree variant install (preferably the
    ``lxml`` variant), ``httplib2`` for timeouts (though it will fall back to
    ``httplib``) and either the ``json`` module that comes with Python 2.5+ or
    ``simplejson``.

More Like This
--------------

To enable the "More Like This" functionality in Haystack, you'll need
to enable the ``MoreLikeThisHandler``. Add the following line to your
``solrconfig.xml`` file within the ``config`` tag::

    <requestHandler name="/mlt" class="solr.MoreLikeThisHandler" />

Spelling Suggestions
--------------------

To enable the spelling suggestion functionality in Haystack, you'll need to
enable the ``SpellCheckComponent``.

The first thing to do is create a special field on your ``SearchIndex`` class
that mirrors the ``text`` field, but has ``indexed=False`` on it. This disables
the post-processing that Solr does, which can mess up your suggestions.
Something like the following is suggested::

    class MySearchIndex(indexes.SearchIndex):
        text = indexes.CharField(document=True, use_template=True)
        # ... normal fields then...
        suggestions = indexes.CharField()
        
        def prepare(self, obj):
            prepared_data = super(NoteIndex, self).prepare(object)
            prepared_data['suggestions'] = prepared_data['text']
            return prepared_data

Then, you enable it in Solr by adding the following line to your
``solrconfig.xml`` file within the ``config`` tag::

    <searchComponent name="spellcheck" class="solr.SpellCheckComponent">

        <str name="queryAnalyzerFieldType">textSpell</str>

        <lst name="spellchecker">
          <str name="name">default</str>
          <str name="field">suggestions</str>
          <str name="spellcheckIndexDir">./spellchecker1</str>
          <str name="buildOnCommit">true</str>
        </lst>
    </searchComponent>

Then change your default handler from::

    <requestHandler name="standard" class="solr.StandardRequestHandler" default="true" />

... to ...::

    <requestHandler name="standard" class="solr.StandardRequestHandler" default="true">
        <arr name="last-components">
            <str>spellcheck</str>
        </arr>
    </requestHandler>

Be warned that the ``<str name="field">suggestions</str>`` portion will be specific to
your ``SearchIndex`` classes (in this case, assuming the main field is called
``text``).


Whoosh
======

Official Download Location: http://bitbucket.org/mchaput/whoosh/

Whoosh is pure Python, so it's a great option for getting started quickly and
for development, though it does work for small scale live deployments. The
current recommended version is 1.3.1+. You can install via PyPI_ using::

    sudo easy_install whoosh
    # ... or ...
    sudo pip install whoosh

Note that, while capable otherwise, the Whoosh backend does not currently
support "More Like This" or faceting. Support for these features has recently
been added to Whoosh itself & may be present in a future release.

.. _PyPI: http://pypi.python.org/pypi/Whoosh/


Xapian
======

Official Download Location: http://xapian.org/download

Xapian is written in C++ so it requires compilation (unless your OS has a
package for it). Installation looks like::

    curl -O http://oligarchy.co.uk/xapian/1.0.11/xapian-core-1.0.11.tar.gz
    curl -O http://oligarchy.co.uk/xapian/1.0.11/xapian-bindings-1.0.11.tar.gz
    
    tar xvzf xapian-core-1.0.11.tar.gz
    tar xvzf xapian-bindings-1.0.11.tar.gz
    
    cd xapian-core-1.0.11
    ./configure
    make
    sudo make install
    
    cd ..
    cd xapian-bindings-1.0.11
    ./configure
    make
    sudo make install

Xapian is a third-party supported backend. It is not included in Haystack
proper due to licensing. To use it, you need both Haystack itself as well as
``xapian-haystack``. You can download the source from
http://github.com/notanumber/xapian-haystack/tree/master. Installation
instructions can be found on that page as well. The backend, written
by David Sauve (notanumber), fully implements the `SearchQuerySet` API and is
an excellent alternative to Solr.