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From Jacques Nadeau <jacq...@apache.org>
Subject Re: [DISCUSS][Format] Time Interval Changes
Date Tue, 02 Apr 2019 15:05:38 GMT
>
> I could go either way, it has some benefits for forward compatibility I
> suppose, but on the other hand YAGNI, if you feel strongly, I'm ok
> including it.  However, the more optional fields we have for a specific
> enum value, makes me lean more towards a new type instead of just an enum.
>
I'm okay with skipping for now. Appreciate the focus on only what we
actually need.



> Could you elaborate on defining standard arithmetic conversions between
> time-delta/duration in seconds and other time unit (days, months, years) as
> part of the standard/format, I'm still not sure I understand what the
> use-case is here.
>

Here goes nothing...

Seems like there are two options for durations:
1) they aren't related to any other type
2) they have a relationship to timestamps and dates.

If 1, then the only thing I could understand is real world duration how
seconds are defined (and fractions thereof). E.g. [1] :D. In this
situation, there is no way to express any unit of time of higher
granularity than a second (e.g. days) since it is up to application
implementer to define the relationship. This severely limits the
expressiveness of the concept. (I can't ever use something TimeUnit.DAYS)
and stops the ability to cover the existing interval YEAR_MONTH type I
believe (since it has a resolution of months).

If 2, then we must define the canonical value of ts + duration, otherwise
duration are somewhat meaningless, thus the proposed translation chart
(which causes its own oddities depending on the resolution of the time type
you are adding to).

That being said, having started to remember previous discussions on this,
I'm most inclined to simply pick #1 and ignore the need for anything more.
The curiousness of interval math in database systems underscores the fact
that it apparently doesn't matter that much. In most cases, today + 3
months is close enough to today + 90 days for government work.

Let's +2 a patch and get it merged quickly so we never have to think about
this again :)

[1]  "the duration of 9,192,631,770 periods
<https://en.wikipedia.org/wiki/Frequency> of the radiation corresponding to
the transition between the two hyperfine levels
<https://en.wikipedia.org/wiki/Hyperfine_structure> of the ground state of
the caesium-133 <https://en.wikipedia.org/wiki/Caesium-133> atom" (at a
temperature of 0 K <https://en.wikipedia.org/wiki/Absolute_zero>)

>

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