Hi!
I was reading the ORM documentation about annotate and aliases. Given
class Paper(models.Model): pass
class Author(models.Model):
paper = models.ForeignKey(Paper, on_delete=models.CASCADE)
name = models.CharField(max_length=100)
and the query
Paper.objects.filter(author__name__contains="Foo").filter(author__name__contains="Bar").annotate(bar=F("author__pk")).filter(bar=123)
Django 2.0.3 generates the query
SELECT ... FROM "x_paper" INNER JOIN "x_author" ON ... INNER JOIN
"x_author" T3 ON ...
WHERE (
"x_author"."name" LIKE %Foo% ESCAPE '\'
AND T3."name" LIKE %Bar% ESCAPE '\'
AND "x_author"."id" = 123)
In other words, the annotate(bar=F("author__pk")) binds bar to the first
join and not the second T3 join. Is this a bug?
I need to find all papers with one author fulfilling a set of criteria and
another author (another as in author1.pk != author2.pk) fulfilling a
different set of criteria.
The only way I can think of to do that is by somehow naming something from
the join, like this
Paper.objects
.filter(author__name__contains="Foo").annotate(foo_pk=F("author__pk"))
.filter(author__name__contains="Bar").annotate(bar_pk=F("author__pk"))
.exclude(foo_pk=F("bar_pk"))
It could also be used to solve related join queries, like "find papers with
authors with the same last name".
The only way I can see out at the moment is generating a query without the
exclude part, then parsing it to find the Tx alias names and putting them
in a RawSQL expression to form the final query.
Ole
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