[Django] #28108: new Pagination object create hit to database

[Django]

#28108: new Pagination object create hit to database
-------------------------------------+-------------------------------------
Reporter: Oleksandr | Owner: nobody
Shtalinberg |
Type: Bug | Status: new
Component: Core | Version: 1.11
(Other) |
Severity: Normal | Keywords: Pagination
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
This line self._check_object_list_is_ordered()
https://github.com/django/django/commit/c4980e28e57f385d8ffed5e32ce373e52ce61049
#diff-bbce48ca2decf49cb1a52079680d2c3aR30
create hit to database when I just create new Pagination object with
Django 1.11

https://travis-ci.org/shtalinberg/django-el-pagination/jobs/224166104
Django 1.8-1.10 don't have that bug - all tests success

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Ticket URL: <https://code.djangoproject.com/ticket/28108>
Django <https://code.djangoproject.com/>
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[Django]

#28108: new Pagination object create hit to database
-------------------------------------+-------------------------------------
Reporter: Oleksandr | Owner: nobody
Shtalinberg |

Type: Bug | Status: closed

Component: Core (Other) | Version: 1.11

Severity: Normal | Resolution: invalid
Keywords: Pagination | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Simon Charette):

* status: new => closed
* resolution: => invalid

Comment:

The extraneous query is executed when the `UnorderedObjectListWarning`
message, which includes the queryset representation, is created as shown
in your build.

{{{
test_num_queries
(el_pagination.tests.templatetags.test_el_pagination_tags.LazyPaginateTest)
... /home/travis/build/shtalinberg/django-el-
pagination/.tox/py27-dj111/lib/python2.7/site-
packages/django/core/paginator.py:112: UnorderedObjectListWarning:
Pagination may yield inconsistent results with an unordered object_list:
<QuerySet [<TestModel: TestModel: 1>, <TestModel: TestModel: 2>,
<TestModel: TestModel: 3>, <TestModel: TestModel: 4>, <TestModel:
TestModel: 5>, <TestModel: TestModel: 6>, <TestModel: TestModel: 7>,
<TestModel: TestModel: 8>, <TestModel: TestModel: 9>, <TestModel:
TestModel: 10>, <TestModel: TestModel: 11>, <TestModel: TestModel: 12>,
<TestModel: TestModel: 13>, <TestModel: TestModel: 14>, <TestModel:
TestModel: 15>, <TestModel: TestModel: 16>, <TestModel: TestModel: 17>,
<TestModel: TestModel: 18>, <TestModel: TestModel: 19>, <TestModel:
TestModel: 20>, '...(remaining elements truncated)...']>
}}}

Making sure to pass an ordered set of objects to `paginate` should solve
your issue.

This could be done by adding `order_by('pk')` to the queryset your
`make_model_instances()` [https://github.com/shtalinberg/django-el-
pagination/blob/a156097afd8fb2be4075b4659a251f7deb954ada/el_pagination/tests/templatetags/test_el_pagination_tags.py#L87
function returns].

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Ticket URL: <https://code.djangoproject.com/ticket/28108#comment:1>