#31723: Lag() with DecimalField crashes on SQLite.
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Reporter: qwango | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 3.0
(models, ORM) |
Severity: Normal | Resolution:
Keywords: Lag | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
Likely an issue due to `SQLiteNumericMixin`
https://github.com/django/django/blob/27c09043da52ca1f02605bf28600bfd5ace95ae4/django/db/models/expressions.py#L16-L28
We could make `Window` inherit from `SQLiteNumericMixin` and make
`SQLiteNumericMixin.as_sqlite` a noop when `getattr(self,
'window_compatible', False)`.
An alternative would be to make `Window` inherit from `SQLiteNumericMixin`
and make its `as_sqlite` special case itself when
`isinstance(self.output_field, 'DecimalField')` with something along
{{{#!python
def as_sqlite(self, compiler, connection):
if isinstance(self.output_field, 'DecimalField'):
copy = self.copy()
source_expressions = copy.get_source_expressions()
source_expressions[0].output_field = FloatField()
copy.set_source_expressions(source_expressions)
return super(Window, copy).as_sqlite(compiler, connection)
return self.as_sql(compiler, connection)
}}}
That would avoid teaching `SQLiteNumericMixin` about window functions and
make sure window compatible functions can be used outside of windows
expressions while being wrapped appropriately.
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Ticket URL: <https://code.djangoproject.com/ticket/31723#comment:2>
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