Trivial example

from stored.queryset import FilterQuerySet
q = FilterQuerySet('Q(text__icontains="sometext")', 'someapp.somemodel')
q.objects.all() #outputs all

loads(dumps(q)).objects.all() #same result

Simple with literals

#define default literals
q0 = FilterQuerySet('Q(text__icontains="{literal_text}")',
                    'someapp.somemodel',
                    literal_parameter='"sometext"')

#new queryset with different `literal_text` value
q1 = q0.literal(literal_text='"some_other_text"').objects.all()
#literals are parsed with safe `ast.literal_eval` and can be taken from user input

#q1 can be pickled and thus user search can be stored in db
#if to keep different `FilterQuerySet` for each user.
loads(dumps(q1)).objects.all() #same result

More complex - user specific search with related fields and persistent parameters

models.py:

from django.db import models
from django.contrib.auth.models import User

from stored.queryset import FilterQuerySet

class RelatedModel(models.Model):
    user = models.ForeignKey(User, blank=True, null=True)#or maybe MtM
    rating = models.IntegerField()

class SomeModel(models.model):
    text = models.CharField()
    related_field = models.ForeignKey(RelatedModel)

views.py:

search_query = 'Q(text__icontains="{search}")\
&Q(related_field__in=related.filter(rating__gte={min_related_rating}))'

default_search_queryset = \
    FilterQuerySet(query, 'someapp.somemodel', min_related_rating='3')

def view(request):
    if not request.user.is_anonymous():
        profile = request.user.get_profile()
        query = loads(profile.search) \
                        if profile.search \
                        else default_search_queryset)

        #query.objects.all() will raise an exception -
        #we have to define `related` variable and `search` literal

        related = RelatedModel.objects.filter(Q(user=request.user)|Q(user__in=[None, '']))

        def store_search(query):
            profile.search = dumps(query)
            profile.save()
    else:
        query = default_search_queryset
        related = RelatedModel.objects.filter(Q(user__in=[None, '']))
        def store_search(query):
            pass

    #define evaluated variables
    actual_query = query(related=related)

    #ALERT: NEVER PASS USER INPUT AS EVALUATED VARIABLES
    #use literals for that

    if request.REQUEST.get('search', None): #bonus: previous search stored too
        actual_query.literals(search=request.REQUEST['search'])


    if request.REQUEST.get('min_rating', None): #override min_rating if required
        actual_query.literals(min_related_rating=request.REQUEST['min_rating'])

    #now we can store it together with last search string and `min_related_rating` parameter
    store_search(actual_query)
    #NOTICE. `related` and any evaluated variables will NOT be stored
    #so next time we have to call query with `related` again.

    return render_to_response('search.html', {'items':actual_query.objects})