Part metadata in plugin not updating

[etrombly]

I'm working on a plugin currently and don't want to extend the DB to store some data, so I'm following the example on the metadata page.

        parts = Part.objects.iterator()
        for part in parts:
            if "lookup_status" in part.metadata.keys():
                match part.metadata["lookup_status"]:
                    case "submitted":
                        part.metadata["lookup_status"] = "updated"
                        # have to save the part for the update to commit, but it seems like it closes the db connection
                        part.save()
                    case "updated":
                        pass
            else:
                part.metadata["lookup_status"] = "submitted"
                part.save()

The above code is called by a scheduled task. The issue I'm having is if I check the metadata immediately after updating it it shows correctly, but on the next task run the metadata would be blank again. So looking at the mptt documentation I thought I might need to save the record (even though it's not in the example), this actually updates the part correctly, but I end up getting an error that the DB connection is closed. It looks like the connection is re-opened fine, but I'm not sure if I'm doing this correctly.

2026-03-16 16:16:39,392 ERROR Failed 'plugin.registry.call_plugin_function' (leopard-princess-hawaii-three) - the connection is closed : Traceback (most recent call last):
  File "/root/.local/lib/python3.11/site-packages/django/db/utils.py", line 98, in inner
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/psycopg/_server_cursor.py", line 121, in fetchmany
    recs = self._conn.wait(self._fetch_gen(size))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/psycopg/connection.py", line 483, in wait
    return waiting.wait(gen, self.pgconn.socket, interval=interval)
                             ^^^^^^^^^^^^^^^^^^
  File "psycopg_binary/pq/pgconn.pyx", line 214, in psycopg_binary.pq.PGconn.socket.__get__
  File "psycopg_binary/pq/pgconn.pyx", line 747, in psycopg_binary.pq._call_int
  File "psycopg_binary/pq/pgconn.pyx", line 727, in psycopg_binary.pq._ensure_pgconn
psycopg.OperationalError: the connection is closed

[matmair]

Either do all database changes atomically or persist the iterator (it is lazy currently)

[etrombly]

Thanks for the help, for anyone else with a similar issue in the future, what worked for me was:

        parts = [part.pk for part in Part.objects.iterator()]
        for part in parts:
            part = Part.objects.get(pk=part)