Error in Queryset with operator | (union queryset) + slice

[vini.gracindo@…]

class Example:
    name = models.CharField(max_length = 30)
    public = models.BooleanField()

>>> Example.objects.create('example 1', False)
<Example: Example object>
>>> Example.objects.create('example 2', False)
<Example: Example object>
>>> Example.objects.create('example 3', True)
<Example: Example object>
>>> Example.objects.create('example 4', True)
<Example: Example object>
>>> Example.objects.create('example 5', False)
<Example: Example object>
>>> query = Example.objects.filter(public = True)
>>> if(query.count() < 3):
...     query = query | Example.objects.filter(public = False).order_by('?')[:1]
...
>>> query.count()
5
>>>

When using the union of querysets to slice it "ignores" the slice and takes all objects where public = false.

[Anssi Kääriäinen]

What should the expected output be? Maybe (pseudoquery):

select * from example
where (original_query_conditions) or pk in (select pk from example where public = false order by random() limit 1)

Or, in this special case this could be written as:

select * from example
where (original_query_conditions) or pk = (select pk from example where public = false order by random() limit 1)

[anonymous]

Expected:

>> query = query | Example.objects.filter(public = False).order_by('?')[:1]
>> print query.count()
3

[Ian Foote]

​PR

[Tim Graham <timograham@…>]

In e1fc07c:

Fixed #17930 -- Allowed ORing (|) with sliced QuerySets.