def METHOD_NAME():
    bind = op.get_bind()
    session = db.Session(bind=bind)
    tables = [
        Annotation,
        Dashboard,
        Database,
        DruidCluster,
        DruidColumn,
        DruidDatasource,
        DruidMetric,
        Slice,
        SqlaTable,
        SqlMetric,
        TableColumn,
    ]
    for table in tables:
        for record in session.query(table).all():
            for col in record.__table__.columns.values():
                if not col.primary_key:
                    if getattr(record, col.name) == "":
                        setattr(record, col.name, None)
        session.commit()
    session.close()