Re: Have I found an interval arithmetic bug?

On Mon, Apr  5, 2021 at 02:01:58PM -0400, Bruce Momjian wrote:
> On Mon, Apr  5, 2021 at 11:33:10AM -0500, Justin Pryzby wrote:
> Well, bug or not, we are not going to change back branches for this, and
> if you want a larger discussion, it will have to wait for PG 15.
> 
> > > https://www.postgresql.org/docs/current/datatype-datetime.html#DATATYPE-INTERVAL-INPUT
> > > « …field values can have fractional parts; for example '1.5 week' or '01:02:03.45'. Such input is converted to
theappropriate number of months, days, and seconds for storage. When this would result in a fractional number of months
ordays, the fraction is added to the lower-order fields using the conversion factors 1 month = 30 days and 1 day = 24
hours.For example, '1.5 month' becomes 1 month and 15 days. Only seconds will ever be shown as fractional on output. »
 
> 
> I see that.  What is not clear here is how far we flow down.  I was
> looking at adding documentation or regression tests for that, but was
> unsure.  I adjusted the docs slightly in the attached patch.

Here is an updated patch, which will be for PG 15.  It updates the
documentation to state:

    The fractional parts are used to compute appropriate values for the next
    lower-order internal fields (months, days, seconds).

It removes the flow from fractional months/weeks to
hours-minutes-seconds, and adds missing rounding for fractional
computations.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.