How to obtain and/or save the queryset criteria to the DB?

Question

I would like to save a queryset criteria to the DB for reuse.

So, if I have a queryset like:

Client.objects.filter(state='AL') 

# I'm simplifying the problem for readability. In reality I could have 
# a very complex queryset, with multiple filters, excludes and even Q() objects.

I would like to save to the DB not the results of the queryset (i.e. the individual client records that have a state field matching 'AL'); but the queryset itself (i.e. the criteria used in filtering the Client model).

The ultimate goal is to have a "saved filter" that can be read from the DB and used by multiple django applications.

At first I thought I could serialize the queryset and save that. But serializing a queryset actually executes the query - and then I end up with a static list of clients in Alabama at the time of serialization. I want the list to be dynamic (i.e. each time I read the queryset from the DB it should execute and retrieve the most current list of clients in Alabama).

---

Edit: Alternatively, is it possible to obtain a list of filters applied to a queryset?

Something like:

qs = Client.objects.filter(state='AL')
filters = qs.getFilters()
print filters

{ 'state': 'AL' }

Answer 1

You can do as jcd says, storing the sql.

You can also store the conditions.

In [44]: q=Q( Q(content_type__model="User") | Q(content_type__model="Group"),content_type__app_label="auth")

In [45]: c={'name__startswith':'Can add'}

In [46]: Permission.objects.filter(q).filter(**c)
Out[46]: [<Permission: auth | group | Can add group>, <Permission: auth | user | Can add user>]

In [48]: q2=Q( Q(content_type__model="User") | Q(content_type__model="Group"),content_type__app_label="auth", name__startswith='Can add')

In [49]: Permission.objects.filter(q2)
Out[49]: [<Permission: auth | group | Can add group>, <Permission: auth | user | Can add user>]

In that example you see that the conditions are the objects c and q (although they can be joined in one object, q2). You can then serialize these objects and store them on the database as strings.

--edit--

If you need to have all the conditions on a single database record, you can store them in a dictionary

{'filter_conditions': (cond_1, cond_2, cond_3), 'exclude_conditions': (cond_4, cond_5)} 

and then serialize the dictionary.