To: pgsql-sql@postgresql.org
From: "Milen A. Radev" <milen@radev.net>
Subject: Re: Floating point type to store numbers
Date: Tue, 17 Apr 2007 22:10:40 +0300
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Radhika Sambamurti написа:
> Hi,
> I am currently using Postgresql to maintain an application which is used
> for trading and back office operations. Currently our monetary fields are
> stored in Varchar. I am finding a huge CPU utilization while converting
> from varchar to float. I think for reasons unknown to me, we originally
> stored $ amounts and rates in varchar. I am planning to convert our tables
> that hold money fields and rates from varchar to float. I do not want to
> convert to numeric because numeric is a special string type.
> 
> The question is: how accurate is floating point numbers in Postgres. We
> are using 7.4 soon to be moving to 8.2.
> I need the accuracy to about 6 decimal points. I have read that floating
> points can convert to numbers in accurately.


I believe the manual is quite clear on that one (
http://www.postgresql.org/docs/current/static/datatype-numeric.html#DATATYPE-FLOAT)
:

" - If you require exact storage and calculations (such as for monetary
amounts), use the numeric type instead."


So if you decide to use floats after this warning you are on your own.


-- 
Milen A. Radev