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
30335	TypeError: unhashable type: 'list' when paginating queryset with KeyTransform annotation	Jaap Roes	Can Sarıgöl	"We have encountered a unexpected error when trying to upgrade an application from Django 2.1 to 2.2. 

In our application we have the requirement to order a queryset on a value that's found in a nested datastructure stored in a JSON field. To do this we use `KeyTransform`s to annotate the queryset with this value and order on this annotation. This queryset is then paginated.

This used to work in Django 2.1, but now raises a `TypeError` in Django 2.2.

I created a minimal example to reproduce the error:

`models.py`:
{{{
from django.db import models
from django.contrib.postgres.fields import JSONField

class Example(models.Model):
    data = JSONField(default=dict)
}}}

`tests.py`:
{{{
from django.test import TestCase
from django.core.paginator import Paginator
from django.contrib.postgres.fields.jsonb import KeyTextTransform, KeyTransform

from .models import Example

class TestKeyTransformPagination(TestCase):
    def setUp(self):
        Example.objects.create(data={
            'translations': [
                {'title': 'Ladies and gentleman'},
                {'title': 'Dames en heren'}
            ]
        })
        Example.objects.create(data={
            'translations': [
                {'title': 'Apples and pears'},
                {'title': 'Appels en peren'}
            ]
        })
        # The next example queryset raises: TypeError: unhashable type: 'list'
        # qs = Example.objects.order_by('data__translations__0__title')
        # qs[0]
        #
        # This is a workaround to achieve the desired ordering
        extract_title = KeyTextTransform('title', KeyTransform('0', KeyTransform('translations', 'data')))
        self.qs = Example.objects.annotate(title=extract_title).order_by('title')

    def test_queryset(self):
        self.assertEqual('Apples and pears', self.qs[0].data['translations'][0]['title'])

    def test_pagination(self):
        # Works on 2.1.x and master, raises TypeError: unhashable type: 'list' on 2.2
        paginator = Paginator(self.qs, per_page=10)
        page = paginator.page(1)
        self.assertEqual('Apples and pears', page.object_list[0].data['translations'][0]['title'])
}}}

While investigating this issue I discovered that this error does not happen on the current master.

After bisecting I can tell that commit 3767c7ff391d5f277e25bca38ef3730ddf9cea9c (Fixed #29244) introduces (or exposes) the exception and 3f32154f40a855afa063095e3d091ce6be21f2c5 (Fixed #30188) fixes the error.

Is it possible to backport the fix for #30188 to Django 2.2 so we can upgrade our application?"	Bug	closed	Database layer (models, ORM)	2.2	Release blocker	fixed	postgresql jsonb keytransform annotation pagination	Can Sarıgöl	Ready for checkin	1	0	0	0	0	0