Re: Precision problems with storage of float/double

Hi Hiroshi

I googled this a little, and I think you are right. 17 and 9 should be enough. I don't have any problems with you changing the patch.

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> Date: Tue, 17 Jun 2014 12:24:51 +0900
> From: inoue(at)tpf(dot)co(dot)jp
> To: nukemd(at)hotmail(dot)com
> CC: pgsql-odbc(at)postgresql(dot)org
> Subject: Re: [ODBC] Precision problems with storage of float/double
>
> (2014/06/16 1:51), John Smith wrote:
>> Hi,
>>
>> I have found that floats and doubles that I save to the database with the ODBC driver may lose precision. The exact bit pattern of my double/float is not what is actually saved in the database. This causes difficulties in situations where you need to compare current record contents with the actual data that was inserted.
>>
>> It appears to be related to conversion from the double/float to text before it is sent to the database.
>>
>> I made a simple patch that appears to fix the issue (by adding more decimal digits in the string conversion), and a test case that tests the issue.
>
> Thanks.
>
> As far as I examined, 9 decimal digits for 32-bit reals and 17 decimal
> digits for 64-bit doubles are sufficient to guarantee the complete
> recovery.
> Is it OK to change decimal digits in your patch to those ones?
>
> Hmm I noticed that server's output should be changed in addition
> to this change. The setting of extra_float_digits should be changed
> from 2 to 3.
>
> regards,
> Hiroshi Inoue
>
>
>
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