id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36598	Django migrations is unable to find remove constraints from non-public schema for Postgres	Salaah Amin	Salaah Amin	"I have a table in another schema (analytics) which is created and managed by Django. The following is a snippet of the table:


{{{
class Meta:
        db_table = '""analytics"".""occupancy""'
        indexes = [models.Index(fields=(""business_id"", ""-dt""))]
        constraints = [
            models.CheckConstraint(
                check=models.Q(occupancy_tables__gte=0.0)
                & models.Q(occupancy_tables___lte=1.0),
                name=""occupancy_tables_between_0_and_1"",
            ),
            models.CheckConstraint(
                check=models.Q(occupancy_covers__gte=0.0)
                & models.Q(occupancy_covers__lte=1.0),
                name=""occupancy_covers_between_0_and_1"",
            ),
        ]
}}}



If i create a new migration that results in these constraints being removed, it breaks.

Here is the traceback:

{{{
Traceback (most recent call last):
  File ""..../manage.py"", line 25, in <module>
    main()
  File ""..../manage.py"", line 21, in main
    execute_from_command_line(sys.argv)
  File ""....django/core/management/__init__.py"", line 442, in execute_from_command_line
    utility.execute()
  File ""....django/core/management/__init__.py"", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""....django/core/management/base.py"", line 412, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""....django/core/management/base.py"", line 458, in execute
    output = self.handle(*args, **options)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""....django/core/management/base.py"", line 106, in wrapper
    res = handle_func(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""....django/core/management/commands/migrate.py"", line 356, in handle
    post_migrate_state = executor.migrate(
                         ^^^^^^^^^^^^^^^^^
  File ""....django/db/migrations/executor.py"", line 135, in migrate
    state = self._migrate_all_forwards(
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""....django/db/migrations/executor.py"", line 167, in _migrate_all_forwards
    state = self.apply_migration(
            ^^^^^^^^^^^^^^^^^^^^^
  File ""....django/db/migrations/executor.py"", line 252, in apply_migration
    state = migration.apply(state, schema_editor)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""....django/db/migrations/migration.py"", line 132, in apply
    operation.database_forwards(
  File ""....django/db/migrations/operations/models.py"", line 659, in database_forwards
    alter_together(
  File ""....django/db/backends/base/schema.py"", line 554, in alter_unique_together
    self._delete_composed_index(
  File ""....django/db/backends/base/schema.py"", line 611, in _delete_composed_index
    raise ValueError(
ValueError: Found wrong number (0) of constraints for ""analytics"".""occupancy""(business_id, dt)
}}}

Taking a look at the code, the problem seems to be caused by `django.lib.backends.postgresql.introspection.DatabaseIntrospection.get_constraints.

The query adds ""pg_catalog.pg_table_is_visible(cl.oid)"". When I ran that query in pgadmin, removing that condition, the missing constraints appeared.

Looking at the postgres docs, pg_table_is_visible searches the search_path. However, I have added the schema to the search path in the db setup in settings.py:

{{{
DATABASES = {
    ...
    ""OPTIONS"": {
            ""options"": ""-c search_path=public,analytics"",
     },
}
}}}

Not sure if this is a misconfiguration on my part (couldn't find anything in Django docs), or if this is a bug/missing feature.
I am able to migrate ok when creating new tables, just deleting constraints seem to be a problem.

Note: I am currently using Django version 4.2. But looking at the source code, this (potential) issue may also be in v5.2."	Bug	closed	Database layer (models, ORM)	4.2	Normal	duplicate	postgres, db, orm	Salaah Amin	Unreviewed	1	0	0	0	0	0