From: Lamar Owen <lamar.owen@wgcr.org>
To: Thomas Lockhart <lockhart@fourpalms.org>
To: Bruce Momjian <pgman@candle.pha.pa.us>
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 12:10:23 -0400
Message-ID: <200207161210.23948.lamar.owen@wgcr.org> (raw)
In-Reply-To: <3D343BEA.1B51B9CD@fourpalms.org>
References: <200207161521.g6GFL5417443@candle.pha.pa.us>
<3D343BEA.1B51B9CD@fourpalms.org>
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?
But, you're telling me floats aren't dumpable/restoreable to exactly the same
value? (????) This can't be good.
--
Lamar Owen
WGCR Internet Radio
1 Peter 4:11
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To: pgsql-sql@postgresql.org
Cc: lamar.owen@wgcr.org, lockhart@fourpalms.org, pgman@candle.pha.pa.us, tgl@sss.pgh.pa.us, tjhart@mac.com, pgsql-hackers@postgresql.org
Subject: Re: [SQL] line datatype
In-Reply-To: <200207161210.23948.lamar.owen@wgcr.org>
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