Postgres introspection don't filter on visible objects.

[Georgi Yanchev]

Several instances of my Django application share the same Postgres database (each in own schema). To specify which schema to use I have in my Django settings:

DATABASES[default']['OPTIONS'] = {
            'options': '-c search_path={}'.format(get_env('POSTGRES_SCHEMA', 'public')),
        }

The problem is that migrations fail, because methods like get_constraints return constraints from other schemas: ​https://github.com/django/django/blob/a3417282ac0464a9a2d1d7685bcfef10feed2597/django/db/backends/postgresql/introspection.py#L145

When I look deeper into that code, it looks that there is a mess with schemas filtering.

1. The first SQL query in get_constraints will use hardcoded schema name public: ​https://github.com/django/django/blob/a3417282ac0464a9a2d1d7685bcfef10feed2597/django/db/backends/postgresql/introspection.py#L175
2. The second SQL in the same method doesn't filter by schema name, so it will return entries from all schemas: ​https://github.com/django/django/blob/a3417282ac0464a9a2d1d7685bcfef10feed2597/django/db/backends/postgresql/introspection.py#L214
3. get_table_list properly filters by using pg_catalog.pg_table_is_visible.
4. get_sequences and get_relations will return entries from all schemas.

[Mariusz Felisiak]

Thanks for this report. I agree that we can use pg_table_is_visible and remove filtering by public schema in get_sequences() and get_constraints(). Django doesn't support schema so it's rather a cleanup to me.

​PR

Comment: get_sequences() will return sequences only from public schema.

[Mariusz Felisiak <felisiak.mariusz@…>]

In c6581a40:

Fixed #30644 -- Made introspection use pg_table_is_visible() instead of filtering by public schema on PostgreSQL.