Re: pg_upgrade and extra_float_digits

Tom Lane wrote:
> Andrew Dunstan <andrew@dunslane.net> writes:
>   
>> Bruce Momjian wrote:
>>     
>>> FYI, I test pg_upgrade by loading the old cluster's regression database
>>> from a pg_dump output file, then after the upgrade, I dump the
>>> regression database of the new cluster and diff the changes.
>>>
>>> The problem I just encountered is that pg_dump uses
>>> extra_float_digits=-3 for 9.0, while previous releases used '2'.  I had
>>> to do hack each server version to get a dump output that would match
>>> without rounding errors --- it did eventually work and validated.
>>>       
>
>   
>> That sounds like a disaster waiting to happen. The server version is 
>> going to affect much more than just this behaviour, surely. Wouldn't it 
>> be better to provide a pg_dump option to provide the extra_float_digits 
>> setting?
>>     
>
> What disaster?  That's only for test purposes, it has nothing to do with
> actual data transfer.
>
>             
>   

Maybe I have misunderstood. How exactly is the server version being 
hacked here? I know it's only for testing, but it still seems to me that 
lying to a program as heavily version dependant as pg_dump is in general 
a bad idea.

cheers

andrew