def log_event(cur, file_id, event_type, old=None, new=None):
    cur.execute(
        """
        INSERT INTO file_events (
            file_id, event_type, event_time,
            old_size, new_size,
            old_hash, new_hash
        )
        VALUES (%s, %s, NOW(), %s, %s, %s, %s)
        """,
        (
            file_id,
            event_type,
            old["size"] if old else None,
            new["size"] if new else None,
            old["content_hash"] if old else None,
            new["content_hash"] if new else None,
        )
    )