InfluxDB 2.x: Error: Unsupported input type for mean aggregate (string to integer)

My InfluxDB 2.x downsampling tasks could not run because of following error.

Error

Could not execute task run; Err: unsupported input type for mean aggregate: string: unsupported input type for mean aggregate: string

Cause

This error occurs because of type conflicts in the same fields respectively in the value of it.

Solution / Workaround

Unfortunately InfluxDB 2.x has no solution for this (or I don't know about them).
That's why we have to convert the type of the "_value" fields and rewrite this in a new measurement.

• Optionally: Create a new bucket (I called them "typeconversion")