django-haystack & SOLR randomise ordering

"""It's a hack for solr backend to apply django-style random ordering
with '?'. Change haystack/backends/solr_backend.py
"""
# .. Somewhere in the beginning
import random

# .. Somewhere in :638, replace content of for-loop into these:
                if order_by.startswith('-'):
                    order_by_list.append('%s desc' % order_by[1:])
                elif order_by.startswith('?'):
                    order_by_list.append('random_%04d desc' % random.randint(0, 9999))
                else:
                    order_by_list.append('%s asc' % order_by)

"""In solr schema, make sure you have:
Inside <types>:
    <fieldType name="random" class="solr.RandomSortField" />

Inside <fields>:
    <dynamicField name="random*" type="random" indexed="true"
        stored="false"/>


"""