Re: Re: [Oledb-dev] double precision error with pg linux server, but not with windows pg server - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Re: [Oledb-dev] double precision error with pg linux server, but not with windows pg server
Date
Msg-id 21828.1179635615@sss.pgh.pa.us
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In response to Re: Re: [Oledb-dev] double precision error with pg linux server, but not with windows pg server  (Shachar Shemesh <shachar@shemesh.biz>)
Responses Re: Re: [Oledb-dev] double precision error with pg linux server, but not with windows pg server  (Shachar Shemesh <shachar@shemesh.biz>)
List pgsql-hackers
Shachar Shemesh <shachar@shemesh.biz> writes:
> Tom Lane wrote:
>> No, not unless you can make the case why this handles NaNs and
>> denormalized numbers compatibly across platforms...
>> 
> NaNs and infinite (plus and minus) should not be a problem.

Really?  Need I point out that these concepts, let alone their
representation, are not standardized in non-IEEE float implementations?

> I'm not sure what denormalized numbers are.

You should find out before proposing representation replacements for
floats.

> What is the scenario in which you would want to tell them apart?
> Likewise, would you really want to tell +0 and -0 apart?

There are competent authorities --- for instance, the guys who created
the IEEE float standard --- who think it's worth distinguishing them.
IIRC (it's been fifteen or so years since I did any serious numerical
analysis) the arguments in favor have mostly to do with preserving
maximal accuracy for intermediate results in a series of calculations.
So maybe you could claim that these arguments are not so relevant to
storage in a database.  But personally I don't think it's the province
of a database to decide that it need not accurately preserve the data
it's given to store.
        regards, tom lane


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