pg_table_is_visible / obj_description / pg_get_indexdef / pg_get_constraintdef / to_regclass / current_schema() / pg_get_serial_sequence not recognized

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Repro:

  SELECT pg_catalog.pg_table_is_visible(1);   -- ERROR
  SELECT obj_description(1, 'pg_class');      -- ERROR
  SELECT pg_get_indexdef(1);                  -- ERROR
  SELECT pg_get_constraintdef(1);             -- ERROR
  SELECT to_regclass('public.foo');           -- ERROR
  SELECT current_schema();                    -- ERROR
  SELECT current_database();                  -- ERROR
  SELECT version();                           -- ERROR
  SELECT pg_get_serial_sequence('t','id');    -- ERROR

Expected:

Standard PostgreSQL behavior for each function.

Observed:

All raise psycopg SyntaxError naming the function. The underlying
catalog tables (pg_class, pg_namespace, pg_attribute, pg_type) are
readable, so only the helper functions are missing.

Why it matters:

Django's introspection layer
(django/db/backends/postgresql/introspection.py) emits these from
get_table_list, get_relations, get_constraints, etc. Any ORM-level
test that runs migrate fails immediately. sqlalchemy, alembic, and
asyncpg's introspection helpers similarly depend on these.