Re: Changing Column Order (Was Re: MySQL vs PostgreSQL.)

Alessio Bragadini wrote:
> On Sat, 2002-10-12 at 11:37, Gavin Sherry wrote:
>
> > I cannot think of any reason why changing column order should be
> > implemented in Postgres. Seems like a waste of time/more code bloat for
> > something which is strictly asthetic.
> >
> > Regardless, I do have collegues/clients who ask when such a feature will
> > be implemented. Why is this useful?
>
> Has column ordering any effect on the physical tuple disposition? I've
> heard discussions about keeping fixed-size fields at the beginning of
> the tuple and similar.
>
> Sorry for the lame question. :-)

Yes, column ordering matches physical column ordering in the file, and
yes, there is a small penalty for accessing any columns after the first
variable-length column (pg_type.typlen < 0). CHAR() used to be a fixed
length column, but with TOAST (large offline storage) it became variable
length too. I don't think there is much of a performance hit, though.

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