Re: 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
bitpattern of my double/float is not what is actually saved in the database. This causes difficulties in situations
whereyou 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
testcase 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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