Convert between durations?

[tisonkun]

Timestamps can be converted between different time unit, but Durations can only be reinterpreted from/to int64.

Is it possible to convert between Durations in different time unit?

pub fn can_cast_types(from_type: &DataType, to_type: &DataType) -> bool {
...
        (Timestamp(_, _), Timestamp(_, _) | ...) => true,
...
        (Int64, Duration(_)) => true,
        (Duration(_), Int64) => true,
...
}

[tisonkun]

cc @alamb @tustvold or if you know who are familiar with this sort of APIs.

[tustvold]

Adding support to the cast kernels for these makes sense to me and can likely follow the pattern for Timestamps

[alamb]

I agree converting durations makes sense.

Here is a similar request from @simonvandel in DataFusion: apache/datafusion#11097

@nrc has done some work recently to improve duration support as well here #6245

[tisonkun]

I'm preparing a PR now.

UPDATE - #6452