From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Bryn Llewellyn <bryn(at)yugabyte(dot)com> |
Cc: | Zhihong Yu <zyu(at)yugabyte(dot)com>, Tom Lane PostgreSQL <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Justin Pryzby <pryzby(at)telsasoft(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> |
Subject: | Re: Have I found an interval arithmetic bug? |
Date: | 2021-07-26 17:35:41 |
Message-ID: | 20210726173541.GA13525@momjian.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general pgsql-hackers |
On Sun, Jul 25, 2021 at 11:56:54AM -0700, Bryn Llewellyn wrote:
> As far as I’ve been able, the PG documentation doesn’t do a good job of
> defining the semantics of any of these operations. Some (like the “justify”
This is because fractional interval values are not used or asked about
often.
> functions” are sketched reasonably well. Others, like interval multiplication,
> are entirely undefined.
Yes, the “justify” functions were requested and implemented because they
met a frequently-requested need unrelated to fractional values, though
they do have spill-up uses.
> This makes discussion of simple test like the two I showed immediately above
> hard. It also makes any discussion of correctness, possible bugs, and proposed
> implementation changes very difficult.
Agreed. With fractional values an edge use-case, we are trying to find
the most useful implementation.
> As I’ve said, my conclusion is that the only safe approach is to create and use
> only “pure” interval values (where just one of the internal fields is
> non-zero). For this reason (and having seen what I decided was the impossibly
> unmemorable rules that my modeled implementation uses) I didn’t look at the
> rules for the other fields that the interval literal allows (weeks, centuries,
> millennia, and so on).
I think the current page is clear about _specifying_ fractional units,
but you are right that multiplication/division of fractional values is
not covered.
--
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.
From | Date | Subject | |
---|---|---|---|
Next Message | Olagoke Akinyemi | 2021-07-26 18:24:29 | pg-audit extension |
Previous Message | Rob Sargent | 2021-07-26 17:20:15 | Re: Recursive Parent-Child Function Bottom Up |
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2021-07-26 17:38:16 | Re: Rename of triggers for partitioned tables |
Previous Message | Tom Lane | 2021-07-26 17:33:29 | Re: Skip temporary table schema name from explain-verbose output. |