docs: public void setTransactionType(final TransactionType transactionType) {
          if (null == schemaName) {
              throw new ShardingException("Please select database, then switch transaction type.");
          }
          if (isSwitchFailed()) {
              throw new ShardingException("Failed to switch transaction type, please terminate current transaction.");
          }
          this.transactionType = transactionType;
      }