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
29442	wrong sql for cast datetime to date in sqlite backend	Mauro	nobody	"""data_dimissione"" is datetime field and I need list of days, so my queryset is like

qs = objects.all().annotate(date_only=Cast(""data_dimissione"", DateField())).values_list('date_only', flat=True).distinct() 

It works on mysql , but django 1.11.10-1~bpo9+1 with sqlite3   3.16.2-5+deb9u1  raise TypeError
{{{
  .....
  File  ""../site-packages/django/db/backends/sqlite3/operations.py"", line 232, in convert_datefield_value
    raise e
TypeError: expected string or buffer
}}}

Reason is  sql query is  like 

SELECT DISTINCT CAST(""ps_ps"".""data_dimissione"" AS date) AS ""date_only"", ........

but data results is 
2018|......
see https://code.djangoproject.com/ticket/28727#comment:6


Correct sql seems
SELECT DISTINCT date(""ps_ps"".""data_dimissione"" ) AS ""date_only"", .

"	Bug	closed	Database layer (models, ORM)	1.11	Normal	duplicate	sqlite3 cast		Unreviewed	0	0	0	0	0	0