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Re: ResultSet getString() result differs in 8.3 jdbc (compared to 8.1), with "real" type

From: Tanel <tanel(dot)ehrenpreis(at)finestmedia(dot)ee>
To: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: ResultSet getString() result differs in 8.3 jdbc (compared to 8.1), with "real" type
Date: 2009-05-15 07:08:54
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-jdbc

Guillaume Cottenceau-2 wrote:
> Tanel <tanel.ehrenpreis 'at'> writes:
>> Hi,
>> I made some searches also, however found nothing exactly related to this
>> problem. We just shifted from using 8.1 driver to 8.3 however seems that
>> 8.3
>> driver handles differently Postgresql floating type values, when using
>> getString() on them ? 
>> For example, when there is "real" type value 20.7 in database and we try
>> to
>> get it through getString() then old 8.1 driver returns nicely 20.7, but
>> new
>> 8.3 driver is returning something like 20.700001.
> Wanting to manipulate precise decimal values with float or double
> datatypes is bound to fail, because the binary representation of
> values make it impossible - it holds the mantissa and the
> exponent, so some rounding must happen. The "display" will depend
> on rounding and so forth. 20.7 doesn't exist "as such" in the
> computer, when using float or double datatypes.
> If you want to manipulate precise decimal numbers, use the SQL
> NUMERIC data type (BigDecimal in java); or else, you can always
> use "fixed point" numbers, e.g. if you need a monetary value you
> may store cent values as an integer (2070 in database to
> represent $20.7) and shift by 100 only for user interfacing.
> Beside, getString() on a floating type value is just wrong, but
> you guessed it already! :)
> -- 
> Guillaume Cottenceau
> -- 
> Sent via pgsql-jdbc mailing list (pgsql-jdbc(at)postgresql(dot)org)
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Yes, it is sometimes quite frustrating when all different kind of data types
are used as Strings. Unfortunately this is quite big enterprise portal that
is running with slightly different versions in 7 countries with ancient
system core that was made some other developers ages ago :) . So we are
trying to cause as little changes at the moment as possible, as testing all
functionality would take a week :) . However I certainly strongly suggest
client to take into plan changing this core system part. 

We are currently using floating types for some additional description values
only, where it is not important if few digits in the end are not exact
(numbers themselves are quite small also), so numeric types using would
probably add considerable overload.... currently the problem was just that
they were quite "ugly" when showed in the portal (etc 27.00001 when using
getString()), no real functionality loss...
As the old 8.1 driverĀ“s getString() did not use 2 extra digits, then at the
moment we were just looking for a quick fix, system could be re-structured
later, but thanx ;)

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Subject: Re: ResultSet getString() result differs in 8.3 jdbc (compared to 8.1), with "real" type
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Subject: Re: COPY support: plan and progress

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