#33319: Query.change_aliases raises an AssertionError
-------------------------------------+-------------------------------------
Reporter: Ömer Faruk Abacı | Owner: Vishal
| Pandey
Type: Bug | Status: assigned
Component: Database layer | Version: 3.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Vishal Pandey):
Replying to [comment:4 Simon Charette]:
Thank you for your helping hand.
I tried two approaches to solve this issue by tweaking `table_alias`
method of Query class, and it works with the above-attested sample code,
but unfortunately, both of them fail with few testcases.
By both the approaches, I am trying to resolve the conflicts between the
change_map's keys and its values
1st approach:
{{{
if alias_list:
from random import choice
alias = '%s%d' % (choice(ascii_uppercase), len(self.alias_map)
+ 1)
alias_list.append(alias)
}}}
Here, I am randomly choosing an uppercase letter as the first character of
alias, this returns different aliases, but a test_case is failing with
this approach, with the following traceback.
{{{
FAIL: test_multiple_search_fields (admin_changelist.tests.ChangeListTests)
[<object object at 0x7fc0aa886cf0>] (search_string='Tiny Desk Concert')
All rows containing each of the searched words are returned, where each
----------------------------------------------------------------------
Traceback (most recent call last):
File "/usr/lib/python3.8/unittest/case.py", line 60, in testPartExecutor
yield
File "/usr/lib/python3.8/unittest/case.py", line 582, in subTest
yield
File
"/home/vishal/Desktop/open_source/django/tests/admin_changelist/tests.py",
line 550, in test_multiple_search_fields
group_changelist = group_model_admin.get_changelist_instance(request)
File
"/home/vishal/Desktop/open_source/django/django/contrib/admin/options.py",
line 742, in get_changelist_instance
return ChangeList(
File
"/home/vishal/Desktop/open_source/django/django/contrib/admin/views/main.py",
line 100, in __init__
self.queryset = self.get_queryset(request)
File
"/home/vishal/Desktop/open_source/django/django/contrib/admin/views/main.py",
line 498, in get_queryset
qs = self.root_queryset.filter(Exists(qs))
File
"/home/vishal/Desktop/open_source/django/django/db/models/query.py", line
977, in filter
return self._filter_or_exclude(False, args, kwargs)
File
"/home/vishal/Desktop/open_source/django/django/db/models/query.py", line
995, in _filter_or_exclude
clone._filter_or_exclude_inplace(negate, args, kwargs)
File
"/home/vishal/Desktop/open_source/django/django/db/models/query.py", line
1002, in _filter_or_exclude_inplace
self._query.add_q(Q(*args, **kwargs))
File
"/home/vishal/Desktop/open_source/django/django/db/models/sql/query.py",
line 1374, in add_q
clause, _ = self._add_q(q_object, self.used_aliases)
File
"/home/vishal/Desktop/open_source/django/django/db/models/sql/query.py",
line 1395, in _add_q
child_clause, needed_inner = self.build_filter(
File
"/home/vishal/Desktop/open_source/django/django/db/models/sql/query.py",
line 1263, in build_filter
condition = filter_expr.resolve_expression(self,
allow_joins=allow_joins)
File
"/home/vishal/Desktop/open_source/django/django/db/models/expressions.py",
line 248, in resolve_expression
c.set_source_expressions([
File
"/home/vishal/Desktop/open_source/django/django/db/models/expressions.py",
line 249, in <listcomp>
expr.resolve_expression(query, allow_joins, reuse, summarize)
File
"/home/vishal/Desktop/open_source/django/django/db/models/sql/query.py",
line 1035, in resolve_expression
clone.bump_prefix(query)
File
"/home/vishal/Desktop/open_source/django/django/db/models/sql/query.py",
line 925, in bump_prefix
self.change_aliases({
File
"/home/vishal/Desktop/open_source/django/django/db/models/sql/query.py",
line 848, in change_aliases
assert set(change_map).isdisjoint(change_map.values())
AssertionError
}}}
In 2nd approach, I have rotated the `alias_prefix` in a circular manner
from T(class variable `alias_prefix` has value T) to Z, then from A to Z,
and so on, and it also works on the above-attested code but fails five
other test cases.
{{{
if alias_list:
alias = '%s%d' % (self.alias_prefix, len(self.alias_map) + 1)
self.alias_prefix = chr(ord(self.alias_prefix)+1) if
chr(ord(self.alias_prefix)+1) <= 'Z' else 'A'
alias_list.append(alias)
}}}
I feel something needs to be tweaked here only to solve the problem, but
because of my limited knowledge of the underlying codebase, I am not being
able to solve it.
I seek help from my fellow senior developers to solve this issue.
--
Ticket URL: <https://code.djangoproject.com/ticket/33319#comment:7>
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