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
28329	Cast() does not work with PositiveIntegerField on MySQL.	Paolo D'Apice	Mariusz Felisiak	"Hi, 

I found that the wrong SQL is generated for MySQL 5.7 when using `django.db.models.functions.Cast`.

Suppose I have a model:
{{{
class Model(models.Model):
    id = models.AutoField()
    string = models.CharField()
}}}
This works correctly, cast a string to integer:
{{{
print Model.objects.annotate(as_int=functions.Cast('string', models.IntegerField())).query
SELECT `Model`.`id`, `Model`.`string`, CAST(`Model`.`string`) AS signed integer) AS `as_int` FROM `Model`
}}}

But if cast to unsigned integer (which is what I need):
{{{
print Model.objects.annotate(as_int=functions.Cast('string', models.PositiveIntegerField())).query
SELECT `Model`.`id`, `Model`.`string`, CAST(`Model`.`string`) AS integer UNSIGNED) AS `as_int` FROM `Model`
}}}

Here is the error:
{{{
Model.objects.annotate(as_int=functions.Cast('string', models.PositiveIntegerField()))
ProgrammingError: (1064, ""You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'integer UNSIGNED) AS `id_int` FROM `Model` at line 1"")
}}}

So it seems that casting to `IntegerField` uses the correct MySQL type `signed integer` but casting to `PositiveInteger` uses the wrong type `integer unsigned` (it should be `unsigned integer`, see the MySQL documentation at https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_cast).

"	Bug	closed	Database layer (models, ORM)	dev	Normal	fixed			Accepted	1	0	0	0	1	0