This is the reference: (not sure if I interpreted it right - sorry, newb :)
"If you use a multiple-table UPDATE statement involving InnoDB tables for which there are foreign key constraints, the MySQL optimizer might process tables in an order that differs from that of their parent/ child relationship. In this case, the statement fails and rolls back. Instead, update a single table and rely on the ON UPDATE capabilities that InnoDB provides to cause the other tables to be modified accordingly. See Section 13.5.5.4, “FOREIGN KEY Constraints”." from: http://dev.mysql.com/doc/refman/5.1/en/update.html + http://www.dbforums.com/mysql/1191227-cannot-delete-update-parent-row-foreign-key-constraint-fails.html On Jan 9, 10:23 pm, Tony <tony.0.tho...@gmail.com> wrote: > I read somewhere that InnoDB cant determine the order to apply DB > operations to rows when the request spans multiple tables??? (i.e. > constraint violation???) Is anyone using MySQL + InnoDB and having > similar issues? or is is it the norm to process models in Django on a > per model basis instead of letting the DB cascade deletes across > models? > > On Jan 8, 11:17 pm, Tony <tony.0.tho...@gmail.com> wrote: > > > Dear List, > > > I'm developing with 1.0.2 and am getting the following error: > > > (1451, 'Cannot delete or update a parent row: a foreign key constraint > > fails (`project/comment_comment`, CONSTRAINT > > `in_reply_to_id_refs_id_35b80077` FOREIGN KEY (`in_reply_to_id`) > > REFERENCES `comment_comment` (`id`))') > > > ... where the Comment model i've defined is: > > > class Comment(models.Model): > > objects = CommentManager() > > > user = models.ForeignKey(User) > > title = models.CharField(max_length=60) > > comment = models.TextField() > > content_type = models.ForeignKey(ContentType) > > object_id = models.PositiveIntegerField() > > owner = generic.GenericForeignKey('content_type', 'object_id') > > in_reply_to = models.ForeignKey('self', null=True, blank=True, > > related_name='reply_to') > > rating = models.FloatField(default=5.00) > > created = models.DateTimeField('date created', auto_now_add=True) > > > ... when trying to delete the owner object (genericforeignkey) and > > when there are two comments pointing to the owner object - one with > > in_reply_to == None, and the other with in_reply_to == the first > > comment. The cascade works fine if I try to delete the first comment, > > but when i'm trying to delete the owner object the error comes up??? > > Could anyone please help me understand why this exception is being > > thrown, and how to possibly fix it? > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
