Simon,
Thanks enormously. A little experimentation and I got that to work!
Brilliant. Am most pleased it was possible. Good ol' Django to the rescue.
The thing I got stuck on for a bit was an assertion failure because qs
was DISTINCT and the or'ed qs was not (the or operation raises a rather
cryptic assertion failure then ;-). But nailed it, by examing the SQL
and yes, one contained a DISTINCT clause so I just added it to the other
and was happy ...
Regards,
Bernd.
Simon Charette wrote:
Hello Bern,
You're actually pretty close to the solution.
You should be able to OR an existing querysets filters by using the
"|" operator
between querysets of the same model. That would be the following:
qs |= Model.objects.filter(Q(...))
Simon
Le mercredi 14 mars 2018 23:45:41 UTC-4, Bernd Wechner a écrit :
Another interesting problem.
Let's say I have a QuerySet which already applies some filters.
It's provided by a third party library mind you, and all you have
is the QuerySet instance.
Now I would like to loosen the filter a bit, ad an ORed filter.
Not a trivial thing it seems. Q objects aren't obviously available
unless we can extract the Q object for the existing filter.
In code the scenario looks like:
|
# A Queryset is buillt with some unknown filter criteria
qs =Model.objects.filter(....)
# All we see in out code is the QuerySet qs. But we want somehow
to add a filter criterion. We can do this:
qs =qs.filter(...)
# and the new filter criteria will be added, but with AND logic.
What if we want to add one with OR logic (loosen the filter some)
# It might look like:
qs =qs |Q(...)
# But does it? How can we add an ORed filter criterion to qs?
|
Basically, there's a chance it's not possible! But if it is, it
would rely on some syntax for combining chained .filter() methods
with an OR logic (which seems constrained to Q objects) or
extracting the current filter from a QuerySet and its constraints
as a Q object, so we can OR a new constraint to it, and then
reapply the filter.
Bit of a mystery to me.
Hoping someone has some insights I'm not getting from the docs here.
Regards,
Bernd.
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