public HiveTxnManager getTxnMgr() {
    return txnMgr;
  }
Get the transaction manager for the current SessionState.
Note that the Driver can be initialized with a different txn manager than the SessionState's
txn manager (HIVE-17482), and so it is preferable to use the txn manager propagated down from
the Driver as opposed to calling this method.
@return transaction manager for the current SessionState
ql/src/java/org/apache/hadoop/hive/ql/session/SessionState.java