Filling null tag values

I recently created a new tag key called “hostname” in my measurement. Previously there was only “host” as a tag key.

As a result, my measurement now has both host and hostname as tag keys. However, this also populates the hostname tag with nulls for the previous data.

What I want to do is populate the value of the null hostname tag values with the host tag values for the previous data.

I am currently using version 1.7.6