Re: [GENERAL] Floating point error

From: Abhijit Menon-Sen <ams(at)2ndQuadrant(dot)com>
To: Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>
Cc: Maciek Sakrejda <m(dot)sakrejda(at)gmail(dot)com>, Daniel Farina <daniel(at)heroku(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Tom Duffey <tduffey(at)trillitech(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [GENERAL] Floating point error
Date: 2013-06-24 06:16:36
Message-ID: 20130624061636.GA1946@toroid.org
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At 2013-03-06 10:04:25 +0000, laurenz(dot)albe(at)wien(dot)gv(dot)at wrote:
>
> How about this elaboration?

Sorry to nitpick, but I don't like that either, on the grounds that if I
had been in Tom Duffey's place, this addition to the docs wouldn't help
me to understand and resolve the problem.

I'm not entirely convinced that any brief mention of extra_float_digits
would suffice, but here's a proposed rewording:

The <xref linkend="guc-extra-float-digits"> setting controls the
number of extra significant digits included when a floating point
value is converted to text for output. With the default value of
<literal>0</literal>, the output is portable to every platform
supported by PostgreSQL. Increasing it will produce output that
is closer to the stored value, but may be unportable.

It's a pretty generic sort of warning, but maybe it would help?

(I'm marking this "Waiting on author" in the CF.)

-- Abhijit

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