Configurable SearchIndex for Haystack

indexes.py

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured

# Python 2.7 has an importlib with import_module; for older Pythons,
# Django's bundled copy provides it.
try:  # pragma: no cover
    from importlib import import_module  # pragma: no cover
except ImportError:  # pragma: no cover
    from django.utils.importlib import import_module  # pragma: no cover

assert hasattr(settings, 'HAYSTACK_SEARCH_INDEX'), "You should define an Haystach search index class in HAYSTACK_SEARCH_INDEX settings. Please edit your settings file accordingly"

try:
    mod_name, klass_name = settings.HAYSTACK_SEARCH_INDEX.rsplit('.', 1)
    mod = import_module(mod_name)
except ImportError, e:
    raise ImproperlyConfigured('Error loading search index class %s: "%s"'
                                % (mod_name, e))
try:
    SearchIndex = getattr(mod, klass_name)
except AttributeError:
    raise ImproperlyConfigured('Module "%s" does not define a search index '
        'class named "%s"' % (mod_name, klass_name))

local_settings.py

HAYSTACK_SEARCH_INDEX = 'haystack.indexes.RealTimeSearchIndex'

settings.py

HAYSTACK_SEARCH_INDEX = 'queued_search.indexes.QueuedSearchIndex'