From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruce Momjian <bruce@momjian.us>
Cc: Bryn Llewellyn <bryn@yugabyte.com>
Cc: Zhihong Yu <zyu@yugabyte.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: Isaac Morland <isaac.morland@gmail.com>
Cc: John W Higgins <wishdev@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Have I found an interval arithmetic bug?
Date: Mon, 12 Apr 2021 19:38:21 -0400
Message-ID: <3135041.1618270701@sss.pgh.pa.us> (raw)
In-Reply-To: <20210412232237.GA4231@momjian.us>
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<20210405163310.GP6592@telsasoft.com>
<20210405180158.GB12179@momjian.us>
<20210408172444.GC6909@momjian.us>
<CALNJ-vR9s8zjGkUrxqLbK5GMS8Rn-o=dxb56gNSaWCHUKQZAvQ@mail.gmail.com>
<CALNJ-vQE-W9K8b_XicbeR6CEkzUsA=CqarkwTLjudYTBpH90uw@mail.gmail.com>
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<20210412161842.GA22319@momjian.us>
<8707105F-C45D-4ACB-8F71-51CE5BED58A5@yugabyte.com>
<20210412232237.GA4231@momjian.us>
Bruce Momjian <bruce@momjian.us> writes:
> On Mon, Apr 12, 2021 at 03:09:48PM -0700, Bryn Llewellyn wrote:
>> After all, you've bitten the bullet now and changed the behavior. This means that the semantics of some extant applications will change. So... in for a penny, in for a pound?
> The docs now say:
> Field values can have fractional parts; for example, <literal>'1.5
> weeks'</literal> or <literal>'01:02:03.45'</literal>. The fractional
> --> parts are used to compute appropriate values for the next lower-order
> internal fields (months, days, seconds).
> meaning fractional years flows to the next lower internal unit, months,
> and no further. Fractional months would flow to days. The idea of not
> flowing past the next lower-order internal field is that the
> approximations between units are not precise enough to flow accurately.
Um, what's the argument for down-converting AT ALL? The problem is
precisely that any such conversion is mostly fictional.
> With my patch, the output is now:
> SELECT INTERVAL '3 years 10.241604 months';
> interval
> ------------------------
> 3 years 10 mons 7 days
> It used to flow to seconds.
Yeah, that's better than before, but I don't see any principled argument
for it not to be "3 years 10 months", full stop.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, bruce@momjian.us, bryn@yugabyte.com, zyu@yugabyte.com, pryzby@telsasoft.com, isaac.morland@gmail.com, wishdev@gmail.com
Subject: Re: Have I found an interval arithmetic bug?
In-Reply-To: <3135041.1618270701@sss.pgh.pa.us>
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