presto-jdbc/src/main/java/io/prestosql/jdbc/PrestoConnection.java/PrestoConnection/close
class PrestoConnection:    @Override
    public void close()
            throws SQLException
    {
        try {
            if (!closed.get() && (transactionId.get() != null)) {
                try (PrestoStatement statement = new PrestoStatement(this)) {
                    statement.internalExecute("ROLLBACK");
                }
            }
        }
        finally {
            closed.set(true);
        }
    }