Hi,

first thanks for this awesome software. But I have some trouble and I don't know how to proceed. First I try to find out what else I could provide for this report to be a good bug report.

First, I use the latest version (v1.14.0) from openSUSE build Service. I know, I should compile it by my self to avoid any other causes for this behavior. But for now I still use this package from there

Here is the location of the file(tsdbRead.c)：https://github.com/taosdata/TDengine/blob/develop/src/tsdb/src/tsdbRead.c

As shown in line 1622, Assigning value from pColIdx->offset to offset here, but that stored value is overwritten before it can be used. Who is interested in revising it？

![image](https://user-images.githubusercontent.com/48907085/137857499-b31b7223-b999-42b1-98ab-5db47989534

Relevant telegraf.conf:

[[outputs.graylog]]
  ## UDP endpoint for your graylog instances.
  servers = ["127.0.0.1:12201"]

Expected behavior:

Input plugin name field (e.g. "name":"log_tail") should be sent with _ prefix. Regarding Gelf specification (https://docs.graylog.org/en/4.1/pages/gelf.html#gelf-payload-specification), all non standard fields should always