r9701 breaks for combinations of values_list and unique - it inserts duplicate references in SQL

[cmutel@…]

r9701 introduces a change that leads to malformed SQL in queries that include values_list and distinct queries, at least in SQLite. A simple example:

class Database(models.Model):
    name = models.TextField()

class Process(models.Model):
    database = models.ForeignKey(Database)
    name = models.TextField()

The query

Database.objects.filter(id__in=Process.objects.filter(id__in=(1,2)).values_list(
'database', flat=True).distinct()) 

produces the following SQL:

SELECT "basic_database"."id", "basic_database"."name" FROM "basic_database" WHERE 
"basic_database"."id" IN (SELECT DISTINCT U0."database_id", U0."database_id" FROM 
"basic_process" U0 WHERE U0."id" IN (1, 2)) LIMIT 21

where U0."database_id" is repeated, and produces an error:

OperationalError: only a single result allowed for a SELECT that is part of an expression

Unfortunately, this is the limit of my Python knowledge, so I don't have a patch to correct this problem.

The query functions perfectly in r9700 and earlier.

[Malcolm Tredinnick]

That query cannot possibly come from the queryset you specify, since that queryset will never generate a limit. It's close, though, and does demonstrate a problem.

The root issue is that qs.values_list(...).values(....) doesn't work properly, which needs fixing.

[Malcolm Tredinnick]

(In [9717]) Fixed #9985 -- qs.values_list(...).values(...) was constructing incorrect SQL.

[(none)]

Milestone post-1.0 deleted