Re: pg_upgrade and extra_float_digits

Andrew Dunstan wrote:
> >>> 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.

The code in pg_dump 9.0 is:
   /*    * If supported, set extra_float_digits so that we can dump float data    * exactly (given correctly
implementedfloat I/O code, anyway)    */   if (g_fout->remoteVersion >= 90000)       do_sql_command(g_conn, "SET
extra_float_digitsTO 3");   else if (g_fout->remoteVersion >= 70400)
 
-->     do_sql_command(g_conn, "SET extra_float_digits TO 2");

The indicated line had to be changed to '3'.  I did not change anything
else, and it was only done in my private CVS tree.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com