public long getMvccFromOperationContext(long group, long nonce) {
    if (nonce == HConstants.NO_NONCE) {
      return Long.MAX_VALUE;
    }
    NonceKey nk = new NonceKey(group, nonce);
    OperationContext result = nonces.get(nk);
    return result == null ? Long.MAX_VALUE : result.getMvcc();
  }
Return the write point of the previous succeed operation.
@param group Nonce group.
@param nonce Nonce.
@return write point of the previous succeed operation.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ServerNonceManager.java