From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Mark Dilger <pgsql@markdilger.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: [SQL] Interval subtracting
Date: Wed, 1 Mar 2006 15:33:33 -0500 (EST)
Message-ID: <200603012033.k21KXX125006@candle.pha.pa.us> (raw)
In-Reply-To: <14834.1141244891@sss.pgh.pa.us>
Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > I don't think we can accept a change that takes a negative and turns it
> > into a positive and negative.
>
> Yeah, I find the patch's changes to the regression results pretty
> disturbing.
>
> Perhaps the correct definition ought to be like "if month part >= 0
> then the reduced day part should be between 0 and 30, otherwise the
> reduced day part should be between 0 and -30". However there are
> still corner cases to worry about. If the original month and day
> parts are of different sign, you might not be able to do such a
> reduction without changing the sign of the month part, consider
> "1 month -95 days". Not clear what to do with this.
>
> I guess I would expect a good result to satisfy one of these three
> cases:
> * month > 0 and 0 <= day < 30
> * month < 0 and -30 < day <= 0
> * month = 0 and -30 < day < 30
> If you believe that then "1 month -95 days" should justify to
> "-2 months -5 days".
I believe it. :-)
--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com
+ If your life is a hard drive, Christ can be your backup. +
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: pgman@candle.pha.pa.us, tgl@sss.pgh.pa.us, pgsql@markdilger.com, pgsql-hackers@postgresql.org
Subject: Re: [SQL] Interval subtracting
In-Reply-To: <200603012033.k21KXX125006@candle.pha.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox