#31639: F objects do not error when referencing transforms.
-------------------------------------+-------------------------------------
Reporter: Baptiste Mispelon | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: master
(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
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* stage: Unreviewed => Accepted
Comment:
I think the underlying issue here is that `F` objects simply don't support
transforms but silently drops them when resolving to `Col`.
For example, given the models you've provided
{{{#!python
Bill.objects.filter(issued_on__year=F('issued_on__year'))
}}}
Results in the following on SQLite
{{{#!sql
SELECT "db_functions_bill"."id", "db_functions_bill"."client_id",
"db_functions_bill"."issued_on" FROM "db_functions_bill" WHERE
django_date_extract('year', "db_functions_bill"."issued_on") =
"db_functions_bill"."issued_on"
}}}
Notice how the right hand side of the filter `__year` transform doesn't
result in wrapping what comes after the `=`.
It's not an issue with `filter`'s compilation, `.annotate` exhibit the
same behaviour
{{{#!python
Bill.objects.annotate(year=F('issued_on__year'))
}}}
{{{#!sql
SELECT "db_functions_bill"."id", "db_functions_bill"."client_id",
"db_functions_bill"."issued_on", "db_functions_bill"."issued_on" AS "year"
FROM "db_functions_bill"
}}}
In the end, references to transforms via `F` is not supported and whether
or not it should be discussed on the mailing list. Accepting the ticket on
the basis that we should at least error out in this case.
--
Ticket URL: <https://code.djangoproject.com/ticket/31639#comment:1>
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