On Tue, Oct 18, 2005 at 02:00:57PM -0400, Neil Conway wrote:
> We could improve on this by reordering fields on-disk to reduce
> alignment/padding requirements, during CREATE TABLE. We'd need to be
> sure to present the same column order back to the client application, of
> course, but that should be possible. The notion of a "physical column
> number" (on-disk position of the column) as well as a "logical column
> numer" (position of the column in the table -- e.g. in SELECT *
> expansion) would also make it easy to implement column reordering in
> ALTER TABLE, which has been requested a few times.
AIUI a patch was submitted but rejected on the basis that it would
break too many client apps that rely on the current catalog setup. And
it was combined with "alter column type" discussion at the time. And a
number of other reasons I didn't understand at the time.
http://archives.postgresql.org/pgsql-patches/2003-11/msg00281.php
http://archives.postgresql.org/pgsql-hackers/2003-11/msg00869.php
Yes, once you seperate physical and logical column ordering this
becomes possible, but you have to do it first :)
Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.