Re: round behavior differs between 8.1.5 and 8.3.7

On Monday 20 April 2009 2:21:31 pm Robert Morton wrote:
> Howdy,
> None of the discussions about rounding so far have addressed what appears
> to be a significant change that occurred at some point between PostgreSQL
> v8.1.5 and v8.3.7. Can someone explain to me the difference between the
> two resultsets below? Additionally I would like to understand what option
> will consistently provide a banker's-round in v8.3.7, if possible.
>
> Here is the query, followed by the resultset for each version:
> SELECT
> round(3.5::numeric) as "rn3.5",
> round(3.5::float8) as "rf3.5",
> dround(3.5::numeric) as "dn3.5",
> dround(3.5::float8) as "df3.5",
> CAST(3.5::numeric as INTEGER) as "cn3.5",
> CAST(3.5::float8 as INTEGER) as "cf3.5",
> round(4.5::numeric) as "rn4.5",
> round(4.5::float8) as "rf4.5",
> dround(4.5::numeric) as "dn4.5",
> dround(4.5::float8) as "df4.5",
> CAST(4.5::numeric as INTEGER) as "cn4.5",
> CAST(4.5::float8 as INTEGER) as "cf4.5"
>
> v8.1.5:
> rn3.5,rf3.5,dn3.5,df3.5,cn3.5,cf3.5,rn4.5,rf4.5,dn4.5,df4.5,cn4.5,cf4.5
> 4,4,4,4,4,4,5,4,4,4,5,4
> v8.3.7:
> rn3.5,rf3.5,dn3.5,df3.5,cn3.5,cf3.5,rn4.5,rf4.5,dn4.5,df4.5,cn4.5,cf4.5
> 4,3,3,3,4,3,5,4,4,4,5,4
>
>
> Thanks,
> Robert

Well it wasn't 8.3.5 :) because:

postgres=# SELECT version();
version
------------------------------------------------------------------------------------------------
PostgreSQL 8.3.5 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 4.2.4 (Ubuntu
4.2.4-1ubuntu3)
(1 row)

postgres=# SELECT
postgres-# round(3.5::numeric) as "rn3.5",
postgres-# round(3.5::float8) as "rf3.5",
postgres-# dround(3.5::numeric) as "dn3.5",
postgres-# dround(3.5::float8) as "df3.5",
postgres-# CAST(3.5::numeric as INTEGER) as "cn3.5",
postgres-# CAST(3.5::float8 as INTEGER) as "cf3.5",
postgres-# round(4.5::numeric) as "rn4.5",
postgres-# round(4.5::float8) as "rf4.5",
postgres-# dround(4.5::numeric) as "dn4.5",
postgres-# dround(4.5::float8) as "df4.5",
postgres-# CAST(4.5::numeric as INTEGER) as "cn4.5",
postgres-# CAST(4.5::float8 as INTEGER) as "cf4.5"
postgres-# ;
rn3.5 | rf3.5 | dn3.5 | df3.5 | cn3.5 | cf3.5 | rn4.5 | rf4.5 | dn4.5 | df4.5 |
cn4.5 | cf4.5
-------+-------+-------+-------+-------+-------+-------+-------+-------+-------+-------+-------
4 | 4 | 4 | 4 | 4 | 4 | 5 | 4 | 4 | 4 |
5 | 4
(1 row)

--
Adrian Klaver
aklaver(at)comcast(dot)net