mapper.min.forbid-nulls has the same behavior as
This mapper function returns the min of all the values found in each sliding window. The associated location and elevation are those of the selected value. If the min value is encountered several times, the selected one is the one that appears first chronologically.
mapper.min.forbid-nulls function can be applied to values of any type, when applied to BOOLEAN types, the value false is considered less than true.
If a value is NULL in the bucket, the result is NULL