#29229: QuerySet.values_list() combined with .extra() or .annotate() may produce
wrong .union()
-------------------------------------+-------------------------------------
Reporter: master | Owner: nobody
Type: Bug | Status: new
Component: Database | Version: master
layer (models, ORM) |
Severity: Release | Keywords: union values_list
blocker |
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
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Regression introduced in 2.0, still present in 2.0.3.
Easy context to reproduce the problem: suppose a Message model, in a
postman app. Only one ordinary field is enough for the demo.
{{{#!python
qs1 = Message.objects.extra(select={'count': 0}).values_list('id',
'count').order_by()
print(qs1.query) # as expected:
# SELECT (0) AS "count", "postman_message"."id"
# FROM "postman_message"
qs2 =
Message.objects.values('somefield').annotate(count=models.Count('pk')).annotate(id=models.Max('pk')).values_list('id',
'count').order_by()
print(qs2.query) # as expected:
# SELECT COUNT("postman_message"."id") AS "count",
MAX("postman_message"."id") AS "id"
# FROM "postman_message" GROUP BY "postman_message"."somefield"
print(qs1.union(qs2).query) # !! WRONG !! the qs2 part is truncated:
# SELECT (0) AS "count", "postman_message"."id" FROM "postman_message"
# UNION
# SELECT MAX("postman_message"."id") AS "id" FROM "postman_message" GROUP
BY "postman_message"."somefield"
}}}
Compared to version 1.11, it comes from this addition in
db/models/sql/compiler.py/get_combinator_sql():
{{{#!python
if not compiler.query.values_select and self.query.values_select:
compiler.query.set_values(self.query.values_select)
}}}
Here, self.query.values_select is ('id',).
For qs2, values_select is indeed empty, as coded in
db/models/sql/query.py/set_values(),
because in this case the two values_list() arguments are managed in
annotation_names[].
--
Ticket URL: <https://code.djangoproject.com/ticket/29229>
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