Truncation problem with adding ManyToMany Fields results in "relation already exists"

[anonymous]

Using Postgres.

When you add a many to many that has long-named tables/fields, you can spill over the length limit and have collisions where South's truncation results in identically-named elements.

Error printed is "psycopg2.ProgrammingError?: relation "model_fields_etc_name_so_long_its_truncated" already exists"

A small test case is attached.

[adamfast@…]

Django project / app that demonstrates the error.

[adamfast@…]

Forgot to mention in the body above that the test project works fine with south left out of installed apps, using Django's normal syncdb mechanism.

[andrew]

The index names are actually generated by Django; I've posted about this to the Django developers mailing list, since it's technically a bug in the core (it doesn't happen in this case since Django doesn't do indexes the same way, but I've recreated it with a different model).

It might well turn out to be a WONTFIX, since it's easy enough to pick shorter table and column names with Meta.db_table and Field.db_column, but we'll see.

[andrew]

Bumping version.

[aball@…]

I'm seeing this too. I'd be willing to help fix it if necessary, but I'd like a little bit more information to go on first. I really do not want to rename my tables.

Andrew, could you point me to your post to the Django developers? I'd also appreciate any additional information about how South index generation differs from what Django would normally do.

[aball@…]

I suppose this is the thread on the django-developers Google group:

​http://groups.google.com/group/django-developers/browse_thread/thread/60129b8e734dd045/6c6b900bae40b4c3?lnk=gst&q=andrew+godwin#6c6b900bae40b4c3

[andrew]

Yes, that's the one. I'm not sure there'll be much decision on this till after 1.2 is released; for now, I recommend working around it by using shorter table names (you _could_ compile postgres, but I don't recommend it).

[aball@…]

The index names should be made shorter automatically in Django 1.2, due to patches on ticket #13434 and #13441 which have made it to the trunk. Django 1.2 is now has a release candidate, but hasn't yet been released.

[andrew]

Excellent, then in this case I'll close the ticket as invalid (since it wasn't solved by us).

[aball@…]

Replying to aball@…:

The index names should be made shorter automatically in Django 1.2, due to patches on ticket #13434 and #13441 which have made it to the trunk. Django 1.2 is now has a release candidate, but hasn't yet been released.

For what it's worth, patching Django 1.1.1 with the patches attached to those tickets works fine.