Re: Have I found an interval arithmetic bug?

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Justin Pryzby <pryzby(at)telsasoft(dot)com>
Cc: Bryn Llewellyn <bryn(at)yugabyte(dot)com>, Zhihong Yu <zyu(at)yugabyte(dot)com>, Isaac Morland <isaac(dot)morland(at)gmail(dot)com>, John W Higgins <wishdev(at)gmail(dot)com>, 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: 2021-04-08 17:24:44
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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.
> > >
> > > « …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

Bruce Momjian <bruce(at)momjian(dot)us>

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

Attachment Content-Type Size
interval.diff text/x-diff 7.0 KB

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