to_char(numeric type, text) rounding instead of truncating
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/15/functions-formatting.html
Description:
I've encountered an issue with to_char(numeric type, text)
Apparently, it uses rounding instead of truncation which leads to
unpexpected results. This is not reflected in the documentation.
My specific example:
select to_Char(1235::real/(2::real+1235::real)*100, '99%')
The expected output was 99%. The output was ##% - since the number was
rounded to 100, there wasn't enough digits in the format.
If I add a digit after the decimal point
select to_char(1235::real/(2::real+1235::real)*100,'90D0%')
The output becomes 99.8%
It would be nice to have this behavior explained in the documentation so
people get more predictable results.
On Fri, 2023-07-21 at 04:56 +0000, PG Doc comments form wrote:
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/15/functions-formatting.html
Description:I've encountered an issue with to_char(numeric type, text)
Apparently, it uses rounding instead of truncation which leads to
unpexpected results. This is not reflected in the documentation.
My specific example:
select to_Char(1235::real/(2::real+1235::real)*100, '99%')
The expected output was 99%. The output was ##% - since the number was
rounded to 100, there wasn't enough digits in the format.
If I add a digit after the decimal point
select to_char(1235::real/(2::real+1235::real)*100,'90D0%')
The output becomes 99.8%It would be nice to have this behavior explained in the documentation so
people get more predictable results.
+1
How about the following:
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5a47ce4343..9421ace77e 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -8505,6 +8505,14 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
</para>
</listitem>+ <listitem>
+ <para>
+ If the format provides for fewer fractional digits than the number being
+ formatted has, <function>to_char()</function> will round the number to
+ the specified number of fractional digits.
+ </para>
+ </listitem>
+
<listitem>
<para>
The pattern characters <literal>S</literal>, <literal>L</literal>, <literal>D</literal>,Yours,
Laurenz Albe
On Wed, Jul 26, 2023 at 07:53:36AM +0200, Laurenz Albe wrote:
On Fri, 2023-07-21 at 04:56 +0000, PG Doc comments form wrote:
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/15/functions-formatting.html
Description:I've encountered an issue with to_char(numeric type, text)
Apparently, it uses rounding instead of truncation which leads to
unpexpected results. This is not reflected in the documentation.
My specific example:
select to_Char(1235::real/(2::real+1235::real)*100, '99%')
The expected output was 99%. The output was ##% - since the number was
rounded to 100, there wasn't enough digits in the format.
If I add a digit after the decimal point
select to_char(1235::real/(2::real+1235::real)*100,'90D0%')
The output becomes 99.8%It would be nice to have this behavior explained in the documentation so
people get more predictable results.+1
How about the following:
I slightly modified your patch and applied it back to PG 11 since all
supported Postgres versions have the same behavior. Thanks.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.