Re: Zero-padding and zero-masking fixes for to_char(float)

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: Zero-padding and zero-masking fixes for to_char(float)
Date: 2015-04-02 18:14:43
Message-ID: 20150402181443.GD941@momjian.us
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On Wed, Apr 1, 2015 at 11:48:37AM -0400, Bruce Momjian wrote:
> This should return something like 15555600000000.000... (per Oracle
> output at the URL above, float4 has 6 significant digits on my compiler)
> but I can't seem to figure how to get printf() to round non-fractional
> parts. I am afraid the only solution is to use printf's %e format and
> place the decimal point myself.

Hearing nothing, I went with the %e approach; patch attached. The new
output looks right:

test=> SELECT to_char(float4 '15555555555555.912345678912345678900000000000000000000000',
repeat('9', 50) || '.' || repeat('9', 50));
to_char
--------------------------------------------------------------------------------------------------------
15555600000000.00000000000000000000000000000000000000000000000000
(1 row)

> The fact I still don't have a complete solution suggests this is 9.6
> material but I still want to work on it so it is ready.

I will keep this patch for 9.6 unless I hear otherwise.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +

Attachment Content-Type Size
to_char.diff text/x-diff 31.5 KB

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