[GemStone-Smalltalk] DateAndTime users' questionnaire

Paul Baumann plbaumann at gmail.com
Fri Jun 19 18:36:33 PDT 2020

I'm excited for this change, it will make a huge performance difference
having dates as immediates.

I had done this in tuning in application code where most beneficial. It
would persist an immediate integer that was seconds, ms, or ns from an
epoch datetime. Replication to gbs was then a very efficiently of course as
cache costs were skipped. The slot contained the integer and accessor
methods made it look like a datetime was stored. The accessor methods used
DateTime extensions (like maybe #ms:fromEpoch:, #seconds:fromEpoch:
#msFromEpoch:, and #secondsFromEpoch:) to do conversions between integer
and DateTime instances according to the epoch and granularity the accessors
had consistently specified for the slot in both objectspaces (gbs and gs).
This allowed for incremental application tuning and epoch control most
efficient for the attribute needs.

The epoch that I selected for most slots was probably 1/1/2000, but it
might have also been more recent if the attribute didn't need older dates
stored efficiently. Sorry, I don't recall what epoch and granularity was
generally most useful for most attributes. If polymorphism can be assumed
then you might as well pick an epoch in the near future and dates forward
will become more efficient.

Paul Baumann

On Fri, Jun 19, 2020, 7:46 PM Martin McClure via GemStone-Smalltalk <
gemstone-smalltalk at lists.gemtalksystems.com> wrote:

> If you use DateAndTime in your GemStone application, we at GemTalk would
> very much appreciate your feedback on the questions below.
> At customer request, we're working on a SmallDateAndTime class for
> GemStone -- a "Special" (immediate) version of DateAndTime that relates
> to DateAndTime similarly to the relationship between SmallInteger and
> LargeInteger. For customers with many persistent DateAndTime instances,
> this should improve both space and time performance.
> There are design tradeoffs in resolution, range, printing, etc., and it
> will help us make better decisions if we know how DateAndTime is being
> used now.
> (1) Which of the following messages do you use to create DateAndTime
> instances?
>   * DateAndTime now
>   * DateAndTime nowWithScale:
>   * DateAndTime fromString:
>   * DateAndTime year:day:hour* or year:month:day:hour*
>   * Other protocol
> (2) Do you need DateAndTimes with resolution finer than a microsecond?
> (3) What is your year range of DateAndTime; do you need or use
> DateAndTimes more than 5/10/50 years into the future (or the past)?
> (4) How do you handle DateAndTime printing?
> (5) Have you created a subclass of DateAndTime or DateAndTimeANSI, or
> added your own methods to DateAndTime or DateAndTimeANSI?  If this is
> general functionality that could be useful to include in the base,
> please let us know.
> (6) DateAndTime instances would need to be immutable, to be
> interoperable with SmallDateAndTime. If you are using methods that do
> update a DateAndTime, such as offset: or beRounded, does your code
> expect the receiver to be modified?
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