[Django] #36598: Django migrations is unable to find remove constraints from non-public schema for Postgres

[Django]

#36598: Django migrations is unable to find remove constraints from non-public
schema for Postgres
-------------------------------------+-------------------------------------
Reporter: Salaah Amin | Type:
| Uncategorized
Status: new | Component: Database
| layer (models, ORM)
Version: 4.2 | Severity: Normal
Keywords: postgres, db, orm | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
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.
--
Ticket URL: <https://code.djangoproject.com/ticket/36598>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#36598: Django migrations is unable to find remove constraints from non-public
schema for Postgres
-------------------------------------+-------------------------------------

Reporter: Salaah Amin | Owner: (none)
Type: Bug | Status: new
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:

Keywords: postgres, db, orm | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Salaah Amin):

* type: Uncategorized => Bug

--
Ticket URL: <https://code.djangoproject.com/ticket/36598#comment:1>