Can't alter column to AutoField on postgreSQL

[pjrharley@…]

After testing my case in ticket #402 I tried it out on postgreSQL and came across the following error:

django.db.utils.DatabaseError?: type "serial" does not exist

I think the problem comes down to the discussion here:

​http://old.nabble.com/ALTER-TABLE-with-TYPE-serial-does-not-work-td21769575.html

[andrew]

It's unfortunate that I'll have to special-case this, but I agree, it needs fixing.

[shibz]

Any workaround for this?

[shibz]

I was able to successfully migrate from an integer field to an auto field in postgres using a few custom commands. For anyone else having this problem, you can try this workaround:

1. Change integer field to auto field in models.
2. Generate auto schemamigration like usual.
3. Edit generated file. Under forward/backward delete the alter_table autofield command.
4. Add the following custom commands in the appropriate function, substituting appropriate column/table names:

def forwards(self, orm):
    db.execute("CREATE SEQUENCE %TABLENAME%_%COLUMNNAME%_seq")
    db.execute("SELECT setval('%TABLENAME%_%COLUMNNAME%_seq', (SELECT MAX(%COLUMNNAME%) FROM %TABLENAME%))")
    db.execute("ALTER TABLE %TABLENAME% ALTER COLUMN %COLUMNNAME% SET DEFAULT nextval('%TABLENAME%_%COLUMNNAME%_seq'::regclass)")


def backwards(self, orm):
    db.execute("ALTER TABLE %TABLENAME% ALTER COLUMN %COLUMNNAME% DROP DEFAULT")
    db.execute("DROP SEQUENCE %TABLENAME%_%COLUMNNAME%_seq")

5. Run migration

I haven't tested the backwards migration, but I don't see any reason why it wouldn't work.

[anonymous]

+1 for fixing this and the vaguely related #833, with both fixed you could drop / change primary keys in postgresql

[anonymous]

I tried the workaround, and now I'm experiencing this problem: ​http://stackoverflow.com/questions/6412962/django-admin-instance-needs-to-have-a-primary-key-value-before-a-many-to-many

Basically every time I tried to add an object of the type that I did this to in the Admin interface, I get this error:
'Team' instance needs to have a primary key value before a many-to-many relationship can be used.

[anonymous]

Don't forget in forwards method, to link the Primary Key and the sequence:

db.execute("ALTER SEQUENCE %TABLENAME%_%COLUMNNAME%_seq OWNED BY %TABLENAME%_%COLUMNNAME%.seq")

Else a call to pg_get_serial_sequence postgresql('%TABLENAME%','%COLUMNNAME%') returns NULL, and last_insert_id or sequences resetting at the end of a loaddata do not work (sequence is not updated with last id value).

[anonymous]

thanks shibz, that worked for me