From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Lamar Owen <lamar.owen@wgcr.org>
Cc: Thomas Lockhart <lockhart@fourpalms.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tim Hart <tjhart@mac.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [SQL] line datatype
Date: Tue, 16 Jul 2002 12:26:49 -0400 (EDT)
Message-ID: <200207161626.g6GGQnk01519@candle.pha.pa.us> (raw)
In-Reply-To: <200207161210.23948.lamar.owen@wgcr.org>
Lamar Owen wrote:
> On Tuesday 16 July 2002 11:29 am, Thomas Lockhart wrote:
> > > > We do need a solution for exact dump/reload of floating-point data,
> > > > but I don't see why the lack of it should be reason to disable access
> > > > to the LINE type.
>
> > > I don't understand why dumping the two point values isn't sufficient.
>
> > Which two point values? LINE is handled as an equation, not as points,
> > unlike the LSEG type which has two points.
>
> > One possibility is to have the external representation *be* the same as
> > LSEG, then convert internally. Then we need to decide how to scale those
> > points; maybe always using a unit vector is the right thing to do...
>
> Lines are entered now by specifying two points, anywhere on the line, right?
> The internal representation is then slope-intercept? Why not allow either
> the 'two-point' entry, or direct entry as slope-intercept? How do we
> represent lines now in output? Do we pick two arbitrary points on the line?
> If so, I can see Thomas' point here, where the original data entry might have
> specified two relatively distant points -- but then there's a precision error
> anyway converting to slope-intercept, if indeed that is the internal
> representation. So why not dump in slope-intercept form, if that is the
> internal representation?
Yow, I can see the pain of having slope/intercept and trying to output
two points. What if we store line internally as two points, and convert
to slope/intercept when needed. That way, it would dump out just as it
was entered.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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, lamar.owen@wgcr.org, lockhart@fourpalms.org, tgl@sss.pgh.pa.us, tjhart@mac.com, pgsql-hackers@postgresql.org
Subject: Re: [SQL] line datatype
In-Reply-To: <200207161626.g6GGQnk01519@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