Re: Have I found an interval arithmetic bug?

From: Zhihong Yu <zyu(at)yugabyte(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, Bryn Llewellyn <bryn(at)yugabyte(dot)com>, Isaac Morland <isaac(dot)morland(at)gmail(dot)com>, John W Higgins <wishdev(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Have I found an interval arithmetic bug?
Date: 2021-04-11 19:57:32
Message-ID: CALNJ-vR9s8zjGkUrxqLbK5GMS8Rn-o=dxb56gNSaWCHUKQZAvQ@mail.gmail.com
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On Thu, Apr 8, 2021 at 10:24 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> 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 the appropriate number of months,
> days, and seconds for storage. When this would result in a fractional
> number of months or days, 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(at)momjian(dot)us> https://momjian.us
> EDB https://enterprisedb.com
>
> If only the physical world exists, free will is an illusion.
>
>
+1 to this patch.

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