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
30027	SQLite (pre 3.25.0) does not support window functions, raises OperationalError	Scott Stevens	nobody	"Window functions are supported in SQLite 3.25.0 and newer, but Python 3.6.7 and 3.7.1 only ships with SQLite 3.21.0. Window function syntax is invalid for older versions.

As per the title, window functions therefore aren't supported, but Django doesn't check the SQLite version or availability of window functions. Instead, when the generated SQL is executed, the `sqlite3` Python library raises the SQLite syntax error as `sqlite3.OperationalError`, which in turn is reraised as `django.db.utils.OperationalError`.

I believe this is not intended behaviour, as it is incredibly confusing, and not documented. Typically, if a database feature is not supported, Django will explicitly raise an error when attempting it, rather than allowing the SQL execution to fail. It is also normally documented.

The following code raises an exception (it should work for any model):

{{{
from django.db.models import F, Window
from django.db.models.functions.window import RowNumber
# import the model

MyModel.objects.annotate(rn=Window(expression=RowNumber(), order_by=[F('pk')]))
}}}


Basic Python code that will also raise `sqlite3.OperationalError`:

{{{
import sqlite3
conn = sqlite3.connect("":memory:"")
c = conn.cursor()
c.execute(""CREATE TABLE t0(x INTEGER PRIMARY KEY, y TEXT)"")
c.execute(""INSERT INTO t0 VALUES (1, 'aaa'), (2, 'ccc'), (3, 'bbb')"")
c.execute(""SELECT x, y, row_number() OVER (ORDER BY y) AS row_number FROM t0 ORDER BY x"")
}}}

Tested on master branch (commit c5568340a525ab9c6898ed02c257394cc47285d7) with Python 3.6.6 64-bit (Windows 10 x64). This likely also affects 2.0 and 2.1 branches."	Bug	closed	Database layer (models, ORM)	2.0	Normal	fixed	window functions, database, sqlite		Accepted	1	0	0	1	0	0