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
34205	Arrayfield constraint issue in 4.1	James Gillard	nobody	"I'd already posted this in the django-users groups and someone had suggested this might be a bug, so am reposting here:

I can't yet work out whether this is a Django bug or how I'm using model constraints... Just upgraded from 4.0.8 to 4.1.4 and have hit this issue when saving this model in the admin. I'd read in the release notes that these constraints would be validated on model save, and that's the code that's leading to this exception. If it's not something I've done, it seems ArrayField isn't working with this new validation of my condition. The same happens for Q(phone_numbers__len__gte=0), and the error disappears if I comment out this condition. It seems the generated code might be wrong, as I see 12 ""%s"" and only 11 elements in params. All it's trying to do is ensure that an empty list isn't considered unique.

When hitting save I now get {{{ IndexError: tuple index out of range }}}

Here's the failing model:

{{{
phone_numbers = ArrayField(models.CharField(max_length=200), default=list, blank=True)

class Meta:
    constraints = [
        models.UniqueConstraint(
           fields=['phone_numbers'],
           condition=~Q(phone_numbers__len=0),
           name='unique_email_phones',
        ),
    ]
)
}}}
"	Uncategorized	new	Database layer (models, ORM)	4.1	Normal				Unreviewed	0	0	0	0	0	0