On Tue, Mar 5, 2013 at 12:03 AM, Albe Laurenz <laurenz.albe@wien.gv.at> wrote:
> I don't think that it is about looking nice.
> C doesn't promise you more than FLT_DIG or DBL_DIG digits of
> precision, so PostgreSQL cannot either.
>
> If you allow more, that would mean that if you store the same
> number on different platforms and query it, it might come out
> differently. Among other things, that would be a problem for
> the regression tests.
Thank you: I think this is what I was missing, and what wasn't clear
from the proposed doc patch. But then how can pg_dump assume that it's
always safe to set extra_float_digits = 3? Why the discrepancy between
default behavior and what pg_dump gets? It can't know whether the dump
is to be restored into the same system or a different one (and AFAICT,
there's not even an option to tweak extra_float_digits there).