presto-main/src/main/java/io/prestosql/transaction/TransactionManager.java/TransactionManager/activateTransaction
class TransactionManager:    default void activateTransaction(Session session, boolean transactionControl, AccessControl accessControl)
    {
        if (!session.getTransactionId().isPresent()) {
            return;
        }

        // reactivate existing transaction
        TransactionId transactionId = session.getTransactionId().get();
        if (transactionControl) {
            trySetActive(transactionId);
        }
        else {
            checkAndSetActive(transactionId);
        }
    }