From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Bruce Momjian <bruce(at)momjian(dot)us> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org> |
Subject: | Re: Zero-padding and zero-masking fixes for to_char(float) |
Date: | 2015-03-24 13:47:56 |
Message-ID: | 20150324134756.GA857409@tornado.leadboat.com |
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Lists: | pgsql-hackers |
On Sun, Mar 22, 2015 at 10:53:12PM -0400, Bruce Momjian wrote:
> On Sun, Mar 22, 2015 at 04:41:19PM -0400, Noah Misch wrote:
> > On Wed, Mar 18, 2015 at 05:52:44PM -0400, Bruce Momjian wrote:
> > > This "junk" digit zeroing matches the Oracle behavior:
> > >
> > > SELECT to_char(1.123456789123456789123456789d, '9.9999999999999999999999999999999999999') as x from dual;
> > > ------
> > > 1.1234567891234568000000000000000000000
> > >
> > > Our output with the patch would be:
> > >
> > > SELECT to_char(float8 '1.123456789123456789123456789', '9.9999999999999999999999999999999999999');
> > > ------
> > > 1.1234567891234500000000000000000000000
> > These outputs show Oracle treating 17 digits as significant while PostgreSQL
> > treats 15 digits as significant. Should we match Oracle in this respect while
> > we're breaking compatibility anyway? I tend to think yes.
>
> Uh, I am hesistant to adjust our precision to match Oracle as I don't
> know what they are using internally.
http://sqlfiddle.com/#!4/8b4cf/5 strongly implies 17 significant digits for
float8 and 9 digits for float4.
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