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
22672	ManyToMany insert fails with integrity error when a foreign key is empty string	leetreveil@…	nobody	"How to reproduce:

{{{#!python
class Tag(models.Model):
    id = models.CharField(_(u'id'), max_length=128, primary_key=True)

class Post(models.Model):
    tags = models.ManyToManyField(Tag, blank=True, null=True)
}}}


{{{#!python
post_obj = Post.objects.get(id='someid')
tag_obj = Tag.objects.get(id='')
post_obj.tags.add(tag_obj)
}}}

So when adding a tag object with it's id as a empty string (which is valid) will fail with django.db.utils.IntegrityError: (1048, ""Column 'tag_id' cannot be null"").

Looking into the generated sql tag_id is being converted to NULL:


{{{
INSERT INTO `post_tags` (`post_id`, `tag_id`) VALUES ('someid', NULL)
}}}

How do we stop the orm from converting tag_id to NULL and allow it to stay as a empty string?"	Uncategorized	closed	Database layer (models, ORM)	1.6	Normal	duplicate			Unreviewed	0	0	0	0	0	0