Faceting

Links

• Faceting

Configuration

In these samples we will be faceting on the category_exact field:

• For faceting, we need to use a field from the model, but not allow SOLR to transform it. To achieve this, the build_solr_schema command will create a string field (rather than text). To do this, set the indexed attribute to False. Here is a sample field from the Haystack SearchIndex class:

  class SnapboardPostIndex(SearchIndex):
      text = CharField(model_attr='text', document=True)
      category_exact = CharField(indexed=False)
  
      def prepare_category_exact(self, obj):
          result = obj.thread.category.label
          return result.strip()
  

• Probably best to use a prepare_ method to generate the field content as using a text template can insert un-wanted new line characters. This is only an issue for SOLR fields of type string as we won’t perform any transformations on the data.

• When generating the SOLR schema.xml file using the build_solr_schema management command, check the indexed attribute to make sure it is set to true. For more information see the Faceting section in the Issues notes.

  Note: Don’t forget to re-start the SOLR server and rebuild the index.

• For faceted search, we need to create a separate urls.py file (perhaps in a search folder):

  from django.conf.urls.defaults import *
  from haystack.forms import FacetedSearchForm
  from haystack.query import SearchQuerySet
  from haystack.views import FacetedSearchView
  
  sqs = SearchQuerySet().facet('category_exact')
  
  urlpatterns = patterns('haystack.views',
      url(r'^$', FacetedSearchView(form_class=FacetedSearchForm, searchqueryset=sqs), name='haystack_search'),
  )
  

  Note:

  • The field name (category_exact) is set in the facet method.

  • Don’t forget to include this urls.py file in the project urls.py e.g:

    urlpatterns = patterns('',
        # Example:
        (r'^search/', include('search.urls')),
    )
    

• This search.html template is a little complicated and needs some more work:

  {% extends "admin/base_site.html" %}
  
  {% block content %}
      <h2>Search</h2>
  
      <form method="get" action=".">
          <table>
              <tbody>
                  {{ form.as_table }}
                  <tr>
                      <td>&nbsp;</td>
                      <td>
                          <input type="submit" value="Search">
                      </td>
                  </tr>
              </tbody>
          </table>
  
          {% if query %}
              <!-- Begin faceting. -->
              <h2>By Category</h2>
              <div>
                  <dl>
                      {% if facets.fields.category_exact %}
                          <dt>Category</dt>
                          {# Provide only the top 5 categories #}
                          {% for category in facets.fields.category_exact|slice:":5" %}
                              <dd><a href="{{ request.get_full_path }}&amp;selected_facets=category_exact:&quot;{{ category.0|urlencode }}&quot;">{{ category.0 }}</a> ({{ category.1 }})</dd>
                          {% endfor %}
                      {% else %}
                          <p>No category facets.</p>
                      {% endif %}
                  </dl>
              </div>
              <!-- End faceting -->
  
              <h3>Results</h3>
  
              {% for result in page.object_list %}
                  <p>
                      {{ result.object.id }}
                      <b>{{ result.model_name }}</b>
                      <a href="{{ result.object.get_absolute_url }}">
                          {% ifequal result.model_name 'post' %}
                              <b>{{ result.object.thread.category.label }}</b>
                              {{ result.object.text|truncatewords:80 }}
                          {% endifequal %}
                          {% ifequal result.model_name 'note' %}
                              {{ result.object.title }}
                              {{ result.object.body|truncatewords:80 }}
                          {% endifequal %}
                      </a>
                  </p>
              {% empty %}
                  <p>No results found.</p>
              {% endfor %}
          {% else %}
              {# Show some example queries to run, maybe query syntax, something else? #}
              <h3>No results...</h3>
          {% endif %}
      </form>
  {% endblock %}
  

Testing

To test the facets:

$ python manage.py shell
In [1]: from haystack.query import SearchQuerySet
In [2]: sqs = SearchQuerySet().facet('category_exact'); sqs.facet_counts()
Out[2]:
{'dates': {},
 'fields': {u'category_exact': [(u'The Best Restaurants\n\n', 258),
                                (u'Good Deals\n\n', 204),
                                (u'Skiing in the Vermont Area\n\n', 192),
                                (u'General Discussion\n\n', 171)]},
 'queries': {}}

…or to search for content at the same time:

sqs = SearchQuerySet().filter(content='feature').facet('category_exact'); sqs.facet_counts()