David Rowley <dgrowleyml@gmail.com> writes:
> I just thought that my idea was good enough and very cheap too, won't all
> numerics that are actually stored in a column have the same scale anyway?
No; unconstrained numeric columns (ie, if you just say "numeric") don't
force their contents to any particular scale. It might be that we don't
have to optimize for that case, since it's not in the SQL spec, but it
is definitely supported by PG.
regards, tom lane