#31679: Django sublty produces incorrect query when the same keyword appears in
both aggregate() and annotate()
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Reporter: StefanosChaliasos | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 3.0
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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I have the following query:
{{{#!python
Model.objects.annotate(foo=F('column')).aggregate(foo=Sum(F('foo')))
}}}
Initially, I was running this query on SQLite and Django was producing a
result (i.e. 0).
When I switched to MySQL this query crushed with the following exception:
{{{
Traceback (most recent call last):
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/utils.py", line 86, in _execute
return self.cursor.execute(sql, params)
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/mysql/base.py", line 74, in execute
return self.cursor.execute(query, args)
File "/dir/.env/lib/python3.8/site-packages/MySQLdb/cursors.py", line
209, in execute
res = self._query(query)
File "/dir/.env/lib/python3.8/site-packages/MySQLdb/cursors.py", line
315, in _query
db.query(q)
File "/dir/.env/lib/python3.8/site-packages/MySQLdb/connections.py",
line 239, in query
_mysql.connection.query(self, query)
MySQLdb._exceptions.OperationalError: (1054, "Unknown column 'foo' in
'field list'")
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "mysql.py", line 15, in <module>
ret2 =
Model.objects.using('mysql').annotate(foo=F('column')).aggregate(foo=Sum(F('foo')))
File "/dir/.env/lib/python3.8/site-packages/django/db/models/query.py",
line 384, in aggregate
return query.get_aggregation(self.db, kwargs)
File "/dir/.env/lib/python3.8/site-
packages/django/db/models/sql/query.py", line 502, in get_aggregation
result = compiler.execute_sql(SINGLE)
File "/dir/.env/lib/python3.8/site-
packages/django/db/models/sql/compiler.py", line 1151, in execute_sql
cursor.execute(sql, params)
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/utils.py", line 100, in execute
return super().execute(sql, params)
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/utils.py", line 68, in execute
return self._execute_with_wrappers(sql, params, many=False,
executor=self._execute)
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/utils.py", line 86, in _execute
return self.cursor.execute(sql, params)
File "/dir/.env/lib/python3.8/site-packages/django/db/utils.py", line
90, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/utils.py", line 86, in _execute
return self.cursor.execute(sql, params)
File "/dir/.env/lib/python3.8/site-
packages/django/db/backends/mysql/base.py", line 74, in execute
return self.cursor.execute(query, args)
File "/dir/.env/lib/python3.8/site-packages/MySQLdb/cursors.py", line
209, in execute
res = self._query(query)
File "/dir/.env/lib/python3.8/site-packages/MySQLdb/cursors.py", line
315, in _query
db.query(q)
File "/dir/.env/lib/python3.8/site-packages/MySQLdb/connections.py",
line 239, in query
_mysql.connection.query(self, query)
django.db.utils.OperationalError: (1054, "Unknown column 'foo' in 'field
list'")
}}}
After examining the SQL query produced by Django, I realized that the
query is not correct.
Specifically, Django produced the following SQL query:
{{{#!sql
SELECT SUM(`foo`) AS `foo` FROM `model`
}}}
Instead of
{{{#!sql
SELECT SUM(`foo`) FROM (SELECT `model`.`column` AS `foo` FROM `model`)
subquery
}}}
The issue appears when a keyword in aggregate function is the same with
one of the keywords in annotate function. I initially thought that Django
does not have any restriction on the keywords used in aggregate (i.e. a
keyword in aggregate can be the same with the name of a column from the
inspected model).
If you think that aggregate should not conflict with the annotate, then
Django should produce a warning as running this query in SQLite subtly
produces an incorrect result.
--
Ticket URL: <https://code.djangoproject.com/ticket/31679>
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