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.. _highlighting-label:
Highlighting
============
Haystack supports two kinds of `Highlighting <https://django-haystack.readthedocs.io/en/latest/highlighting.html>`_,
and we support them both.
#. SearchQuerySet highlighting. This kind of highlighting requires a search backend which has support for
highlighting, such as Elasticsearch or Solr.
#. Pure python highlighting. This implementation is somewhat slower, but enables highlighting support
even if your search backend does not support it.
.. note::
The highlighter will always use the ``document=True`` field on your index to hightlight on.
See examples below.
SearchQuerySet Highlighting
---------------------------
In order to add support for ``SearchQuerySet().highlight()``, all you have to do is to add the
:class:`drf_haystack.filters.HaystackHighlightFilter` to the ``filter_backends`` in your view. The ``HaystackSerializer`` will
check if your queryset has highlighting enabled, and render an additional ``highlighted`` field to
your result. The highlighted words will be encapsulated in an ``<em>words go here</em>`` html tag.
**Example view with highlighting enabled**
.. code-block:: python
from drf_haystack.viewsets import HaystackViewSet
from drf_haystack.filters import HaystackHighlightFilter
from .models import Person
from .serializers import PersonSerializer
class SearchViewSet(HaystackViewSet):
index_models = [Person]
serializer_class = PersonSerializer
filter_backends = [HaystackHighlightFilter]
Given a query like below
.. code-block:: none
/api/v1/search/?firstname=jeremy
We would get a result like this
.. code-block:: json
[
{
"lastname": "Rowland",
"full_name": "Jeremy Rowland",
"firstname": "Jeremy",
"highlighted": "<em>Jeremy</em> Rowland\nCreated: May 19, 2015, 10:48 a.m.\nLast modified: May 19, 2015, 10:48 a.m.\n"
},
{
"lastname": "Fowler",
"full_name": "Jeremy Fowler",
"firstname": "Jeremy",
"highlighted": "<em>Jeremy</em> Fowler\nCreated: May 19, 2015, 10:48 a.m.\nLast modified: May 19, 2015, 10:48 a.m.\n"
}
]
Pure Python Highlighting
------------------------
This implementation make use of the haystack ``Highlighter()`` class.
It is implemented as :class:`drf_haystack.serializers.HighlighterMixin` mixin class, and must be applied on the ``Serializer``.
This is somewhat slower, but more configurable than the :class:`drf_haystack.filters.HaystackHighlightFilter` filter class.
The Highlighter class will be initialized with the following default options, but can be overridden by
changing any of the following class attributes.
.. code-block:: python
highlighter_class = Highlighter
highlighter_css_class = "highlighted"
highlighter_html_tag = "span"
highlighter_max_length = 200
highlighter_field = None
The Highlighter class will usually highlight the ``document_field`` (the field marked ``document=True`` on your
search index class), but this may be overridden by changing the ``highlighter_field``.
You can of course also use your own ``Highlighter`` class by overriding the ``highlighter_class = MyFancyHighLighter``
class attribute.
**Example serializer with highlighter support**
.. code-block:: python
from drf_haystack.serializers import HighlighterMixin, HaystackSerializer
class PersonSerializer(HighlighterMixin, HaystackSerializer):
highlighter_css_class = "my-highlighter-class"
highlighter_html_tag = "em"
class Meta:
index_classes = [PersonIndex]
fields = ["firstname", "lastname", "full_name"]
Response
.. code-block:: json
[
{
"full_name": "Jeremy Rowland",
"lastname": "Rowland",
"firstname": "Jeremy",
"highlighted": "<em class=\"my-highlighter-class\">Jeremy</em> Rowland\nCreated: May 19, 2015, 10:48 a.m.\nLast modified: May 19, 2015, 10:48 a.m.\n"
},
{
"full_name": "Jeremy Fowler",
"lastname": "Fowler",
"firstname": "Jeremy",
"highlighted": "<em class=\"my-highlighter-class\">Jeremy</em> Fowler\nCreated: May 19, 2015, 10:48 a.m.\nLast modified: May 19, 2015, 10:48 a.m.\n"
}
]
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