#27245: can't revert migration with index_together with one field
     Reporter:  rm_            |      Owner:  nobody
         Type:  Bug            |     Status:  new
    Component:  Uncategorized  |    Version:  1.8
     Severity:  Normal         |   Keywords:
 Triage Stage:  Unreviewed     |  Has patch:  0
Easy pickings:  0              |      UI/UX:  0
 With django 1.8.14 i added a composite index with one field (lame, sorry!)
 because the field is from an abstract model and it seemed the cleanest way
 to handle that:

 +    class Meta:
 +        index_together = ['owner']

 The migrations got created and applied finely:
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals

 from django.db import migrations, models

 class Migration(migrations.Migration):

     dependencies = [
         ('foobar', '0002_auto_20160315_1805'),

     operations = [

 Problem is i can't revert the migration:

   File "manage.py", line 10, in <module>
   File "/venv/local/lib/python2.7/site-
 packages/django/core/management/__init__.py", line 354, in
   File "/venv/local/lib/python2.7/site-
 packages/django/core/management/__init__.py", line 346, in execute
   File "/venv/local/lib/python2.7/site-
 packages/django/core/management/base.py", line 394, in run_from_argv
     self.execute(*args, **cmd_options)
   File "/venv/local/lib/python2.7/site-
 packages/django/core/management/base.py", line 445, in execute
     output = self.handle(*args, **options)
   File "/venv/local/lib/python2.7/site-
 packages/django/core/management/commands/migrate.py", line 222, in handle
     executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
   File "/venv/local/lib/python2.7/site-
 packages/django/db/migrations/executor.py", line 112, in migrate
     self.unapply_migration(states[migration], migration, fake=fake)
   File "/venv/local/lib/python2.7/site-
 packages/django/db/migrations/executor.py", line 168, in unapply_migration
     state = migration.unapply(state, schema_editor)
   File "/venv/local/lib/python2.7/site-
 packages/django/db/migrations/migration.py", line 162, in unapply
     operation.database_backwards(self.app_label, schema_editor,
 from_state, to_state)
   File "/venv/local/lib/python2.7/site-
 packages/django/db/migrations/operations/models.py", line 415, in
     return self.database_forwards(app_label, schema_editor, from_state,
   File "/venv/local/lib/python2.7/site-
 packages/django/db/migrations/operations/models.py", line 411, in
     getattr(new_model._meta, self.option_name, set()),
   File "/venv/local/lib/python2.7/site-
 packages/django/db/backends/base/schema.py", line 336, in
     self._delete_composed_index(model, fields, {'index': True},
   File "venv/local/lib/python2.7/site-
 packages/django/db/backends/base/schema.py", line 349, in
     ", ".join(columns),
 ValueError: Found wrong number (2) of constraints for

 So the easy way to fix this is to don't permit te creation of a migration
 with less than two fields. OTOH it would be quite cool to use the non
 composite way of removing an index if the constraints are not enough.
 Whatever you decide i can spend some time on the fix.

Ticket URL: <https://code.djangoproject.com/ticket/27245>
Django <https://code.djangoproject.com/>
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