Possible bug - when migrating and removing unique constraint.

[jenlu]

Possible bug - when migrating and removing unique constraint.

Postgres 9.4.1 / 9.5.7 + Django 1.9.5 + psycopg 2.6.1

——

My setup is models/database representing sports events, and with competitors in different events.

Each competitor in different sports has for their model/class:

class Meta:

unique_together = ('event', 'number')

i.e. ensure a unique starting number in an event, now we are relaxing (removing this constraint)
this but having issues when migrating.

The above is represented in postgress as a UNIQUE constraint
and in all models.py the above constraint is as-above — but in pg it is represented as

(i) UNIQUE (event_id, number)

and sometimes as...

(ii) UNIQUE (number, event_id)

…and now when doing migration - for all tables where it is represented as (i) everything
goes well, but in tables where (ii) the following error:

File "/Users/XXX/.virtualenvs/ssi195_2711/lib/python2.7/site-packages/django/db/migrations/migration.py", line 123, in apply

operation.database_forwards(self.app_label, schema_editor, old_state, project_state)

File "/Users/XXX/.virtualenvs/ssi195_2711/lib/python2.7/site-packages/django/db/migrations/operations/models.py", line 359, in database_forwards

getattr(new_model._meta, self.option_name, set()),

File "/Users/XXX/.virtualenvs/ssi195_2711/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 318, in alter_unique_together

self._delete_composed_index(model, fields, {'unique': True}, self.sql_delete_unique)

File "/Users/XXX/.virtualenvs/ssi195_2711/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 347, in _delete_composed_index

", ".join(columns),

ValueError: Found wrong number (0) of constraints for match_ppc_ppccompetitor(event_id, number)

So seems to need to do some migrations manually and no biggie - but yet strange and unsure if Django or pg issue….

/ Jens