RE: postgres_fdw - cached connection leaks if the associated user mapping/foreign server is dropped

Hi

I have an issue about the existing testcase.

"""
-- Test that alteration of server options causes reconnection SELECT c3, c4 FROM ft1 ORDER BY c3, c1 LIMIT 1; -- should work ALTER SERVER loopback OPTIONS (SET dbname 'no such database'); SELECT c3, c4 FROM ft1 ORDER BY c3, c1 LIMIT 1; -- should fail DO $d$
BEGIN
EXECUTE $$ALTER SERVER loopback
OPTIONS (SET dbname '$$||current_database()||$$')$$;
END;
$d$;
SELECT c3, c4 FROM ft1 ORDER BY c3, c1 LIMIT 1; -- should work again """

IMO, the above case is designed to test the following code[1]:
With the patch, it seems the following code[1] will not work for this case, right?
(It seems the connection will be disconnect in pgfdw_xact_callback)

I do not know does it matter, or should we add a testcase to cover that?

[1] /*
* If the connection needs to be remade due to invalidation, disconnect as
* soon as we're out of all transactions.
*/
if (entry->conn != NULL && entry->invalidated && entry->xact_depth == 0)
{
elog(DEBUG3, "closing connection %p for option changes to take effect",
entry->conn);
disconnect_pg_server(entry);
}

Best regards,
houzj