id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
31926	Queryset crashes when recreated from a pickled query with FilteredRelation used in aggregation.	Beda Kosata	David Wobrock	"I am pickling query objects (queryset.query) for later re-evaluation as per https://docs.djangoproject.com/en/2.2/ref/models/querysets/#pickling-querysets. However, when I tried to rerun a query that contains a {{{ FilteredRelation }}} inside a filter, I get an {{{ psycopg2.errors.UndefinedTable: missing FROM-clause entry for table ""t3"" }}} error.

I created a minimum reproducible example.

**models.py**

{{{
from django.db import models


class Publication(models.Model):

    title = models.CharField(max_length=64)


class Session(models.Model):

    TYPE_CHOICES = (('A', 'A'), ('B', 'B'))

    publication = models.ForeignKey(Publication, on_delete=models.CASCADE)
    session_type = models.CharField(choices=TYPE_CHOICES, default='A', max_length=1)
    place = models.CharField(max_length=16)
    value = models.PositiveIntegerField(default=1)
}}}


**The actual code to cause the crash**:

{{{
import pickle

from django.db.models import FilteredRelation, Q, Sum

from django_error.models import Publication, Session


p1 = Publication.objects.create(title='Foo')
p2 = Publication.objects.create(title='Bar')
Session.objects.create(publication=p1, session_type='A', place='X', value=1)
Session.objects.create(publication=p1, session_type='B', place='X', value=2)
Session.objects.create(publication=p2, session_type='A', place='X', value=4)
Session.objects.create(publication=p2, session_type='B', place='X', value=8)
Session.objects.create(publication=p1, session_type='A', place='Y', value=1)
Session.objects.create(publication=p1, session_type='B', place='Y', value=2)
Session.objects.create(publication=p2, session_type='A', place='Y', value=4)
Session.objects.create(publication=p2, session_type='B', place='Y', value=8)

qs = Publication.objects.all().annotate(
    relevant_sessions=FilteredRelation('session', condition=Q(session__session_type='A'))
).annotate(x=Sum('relevant_sessions__value'))
# just print it out to make sure the query works
print(list(qs))

qs2 = Publication.objects.all()
qs2.query = pickle.loads(pickle.dumps(qs.query))
# the following crashes with an error
#     psycopg2.errors.UndefinedTable: missing FROM-clause entry for table ""t3""
#     LINE 1: ...n"".""id"" = relevant_sessions.""publication_id"" AND (T3.""sessio...
print(list(qs2))
}}}

In the crashing query, there seems to be a difference in the {{{ table_map }}} attribute - this is probably where the {{{ t3 }}} table is coming from.

Please let me know if there is any more info required for hunting this down.

Cheers
Beda

p.s.- I also tried in Django 3.1 and the behavior is the same.
p.p.s.- just to make sure, I am not interested in ideas on how to rewrite the query - the above is a very simplified version of what I use, so it would probably not be applicable anyway."	Bug	closed	Database layer (models, ORM)	2.2	Normal	fixed		David Wobrock	Accepted	1	0	0	0	0	0