django.db.utils.IntegrityError when migrating a Postgres database.

[danielbraun]

Trying to upgrade a small Postgres database with the added PositionField.
Using Django 1.7 with its new built-in migrations.

django.db.utils.IntegrityError: check constraint "minisites_page_position_check" is violated by some row

I eventually ditched this app and used s plain IntegerField instead (sadly)

[bashu]

can confirm this...

[ghost]

Same here

[navyad]

facing same issue.

[smcoll]

Appears to have something to do with PositionField.get_internal_type() which reports to the database that it is a PositiveIntegerField. i think this causes a constraint to be written such that the value cannot be less than zero, which is a problem since the migration is setting the default to -1.

@jpwatts what is the benefit of overriding get_internal_type()?

[jpwatts]

It tells the database that it's a PositiveIntegerField because all valid positions are >= 0. Negative positions are shorthand for positions relative to the end of a collection. You can use them in code, but they are supposed to be resolved to absolute positions prior to being sent to the database. It looks like that isn't happening, but I don't think the fix is to remove the database constraint—it's to make sure invalid positions don't get sent to the database in the first place.

[danielbraun]

Just tested it again, and it still happens.
Just to clarify, I added a new field. Is it possible that the field's definition is missing a default value?

[smcoll]

It seems that Django migrations is likely using the default value of -1 at the database level when creating the new column for existing records, which is invalid for a PositiveIntegerField

[Solanar]

Using kwarg default=0 seems to cause the error to go away.

[deepanshu-nickelfox]

You can simply change each negative value from your Database manually or create a function for that.
(incase if you are trying to SmallIntegerField() -> PositiveSmallIntegerField()

This works for me.