why this happen? after build tsi index

_Describe the issue here._

##### Relevant URLs
- https://docs.influxdata.com/influxdb/v1.8/administration/rebuild-tsi-index/
- _Provide other relevant URLs (project issues, community threads, etc.)_

After rebuild the tsi index ,I find the field_keys contains two same fieldkey addrNum,but one is integer one is string,why this happen?

Start with the linked rebuild-tsi-index documentation and the reported TSI index behavior around field_keys. Reproduce the addrNum entries and inspect the available index and field metadata; done means determining whether the differing integer and string types are expected or a defect, with evidence recorded.

Written by the indexing model from the issue text.