presto-hive/src/main/java/io/prestosql/plugin/hive/HiveConnector.java/HiveConnector/getMetadata
class HiveConnector:    @Override
    public ConnectorMetadata getMetadata(ConnectorTransactionHandle transaction)
    {
        ConnectorMetadata metadata = transactionManager.get(transaction);
        checkArgument(metadata != null, "no such transaction: %s", transaction);
        return new ClassLoaderSafeConnectorMetadata(metadata, classLoader);
    }