public TimeZone getSessionTimeZone() {
    IClientSession session = currSession.get();
    if (session != null) {
      return session.getTimeZone();
    } else {
      // only used for test
      return TimeZone.getTimeZone(ZoneId.systemDefault());
    }
  }
update connection idle time after execution.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/protocol/session/SessionManager.java