@Override
  public String getTimestampPrecision()
      throws IoTDBConnectionException, StatementExecutionException {
    String timestampPrecision = "ms";
    for (int i = 0; i < RETRY; i++) {
      ISession session = getSession();
      try {
        timestampPrecision = session.getTimestampPrecision();
        putBack(session);
        return timestampPrecision;
      } catch (TException e) {
        // TException means the connection is broken, remove it and get a new one.
        LOGGER.warn("getTimestampPrecision failed", e);
        cleanSessionAndMayThrowConnectionException(session, i, new IoTDBConnectionException(e));
      } catch (RuntimeException e) {
        putBack(session);
        throw e;
      } catch (Throwable e) {
        LOGGER.error("unexpected error in getTimestampPrecision", e);
        putBack(session);
        throw new RuntimeException(e);
      }
    }
    return timestampPrecision;
  }
insert data in one row, if you want improve your performance, please use insertRecords method
or insertTablet method

@see Session#insertRecords(List, List, List, List, List)
@see Session#insertTablet(Tablet)
iotdb-client/session/src/main/java/org/apache/iotdb/session/pool/SessionPool.java