#27828: ORM crash on F('date_field') - F('int_field') on PostgreSQL -------------------------------------+------------------------------------- Reporter: Vytis | Owner: nobody Banaitis | Type: Bug | Status: new Component: Database | Version: 1.10 layer (models, ORM) | Severity: Normal | Keywords: Triage Stage: | Has patch: 0 Unreviewed | Needs documentation: 0 | Needs tests: 0 Patch needs improvement: 0 | Easy pickings: 0 UI/UX: 0 | -------------------------------------+------------------------------------- PostgreSQL allows to use subtraction with a date and an int, returning a date. The integer is taken as a time delta in days.
I was trying to use this in Django. {{{#!python class DateModel(models.Model): date_field = models.DateField() int_field = models.IntegerField() }}} {{{#!python In [3]: qs = DateModel.objects.annotate(result=ExpressionWrapper(F('date_field') - F('int_field'), output_field=DateField())) }}} However, this query crashes: {{{#!python In [4]: qs.all() Out[4]: --------------------------------------------------------------------------- ProgrammingError Traceback (most recent call last) /home/vytis/src/django/django/db/backends/utils.py in execute(self, sql, params) 61 else: ---> 62 return self.cursor.execute(sql, params) 63 ProgrammingError: function age(date, integer) does not exist LINE 1: ...del"."date_field", "myapp_datemodel"."int_field", age("myapp... ^ HINT: No function matches the given name and argument types. You might need to add explicit type casts. }}} Generated SQL: {{{ SELECT "myapp_datemodel"."id", "myapp_datemodel"."date_field", "myapp_datemodel"."int_field", age("myapp_datemodel"."date_field", "myapp_datemodel"."int_field") AS "result" FROM "myapp_datemodel" }}} While looking for a solution, I came across a typo in django/db/models/expressions.py (introduced in [changeset:"766afc22a1dfa7d34a08de85356b7bc9dba025e7" 766afc22]): https://github.com/django/django/blob/9718fa2e8abe430c3526a9278dd976443d4ae3c6/django/db/models/expressions.py#L386 Note the `lhs_output` on both sides of operation. Fixing this typo resolves the crash. -- Ticket URL: <https://code.djangoproject.com/ticket/27828> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To post to this group, send email to django-updates@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/049.433349467209f749f240b55df1055acb%40djangoproject.com. For more options, visit https://groups.google.com/d/optout.