CODEWITHSUNDEEP
pythondjangodjango-models
Paul D. Waite
Paul D. Waite

Reputation: 98816

How can I find the union of two Django querysets?

I’ve got a Django model with two custom manager methods. Each returns a different subset of the model’s objects, based on a different property of the object.

Is there any way to get a queryset, or just a list of objects, that’s the union of the querysets returned by each manager method?

Upvotes: 130

Views: 85237

Answers (4)

The Matrix
The Matrix

Reputation: 1338

When combining or operations, like in this example:

a = a1 | a2
ab = a | b

the ab result contains a lot of results. distinct() can be called but it tries too much time to be executed even if I exec

ab = a.distinct() | b.distinct()

Upvotes: 0

Jose Cherian
Jose Cherian

Reputation: 7737

Starting from version 1.11, django querysets have a builtin union method.

q = q1.union(q2) #q will contain all unique records of q1 + q2
q = q1.union(q2, all=True) #q will contain all records of q1 + q2 including duplicates
q = q1.union(q2,q3) # more than 2 queryset union

See my blog post on this for more examples.

Upvotes: 72

Xianxing
Xianxing

Reputation: 321

I would suggest using 'query1.union(query2)' instead of 'query1 | query2'; I got different results from the above two methods and the former one is what I expected. The following is what I had come across:

print "union result:"
for element in query_set1.union(query_set2):
    print element

print "| result:"
for element in (query_set1 | query_set2):
    print element

result:

union result:
KafkaTopic object
KafkaTopic object
KafkaTopic object
KafkaTopic object
KafkaTopic object

| result:
KafkaTopic object
KafkaTopic object

Upvotes: 11

Jordan Reiter
Jordan Reiter

Reputation: 21002

This works and looks a bit cleaner:

records = query1 | query2

If you don't want duplicates, then you will need to append .distinct():

records = (query1 | query2).distinct()

Upvotes: 231

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