Re: [PATCHES] ALTER TABLE ... SET TABLESPACE

On Mon, 21 Jun 2004, Tom Lane wrote:

> Gavin Sherry <swm@linuxworld.com.au> writes:
> > On Sun, 20 Jun 2004, Tom Lane wrote:
> >> Maybe you have to dump each block into WAL as you copy it.
> >> That would be kinda ugly ... though in point of fact less of a WAL load
> >> than writing individual tuples ...
>
> > Should I use the WAL-enabled case of  _bt_blwritepage() as a guide here?
>
> Yeah, actually that is a very good parallel.  If PITR archiving isn't
> turned on, you don't have to dump pages into WAL; you can substitute
> an fsync before commit, instead.  And if it's a temp table then you
> don't have to do either.  (Not sure anyone would ever do SET TABLESPACE
> on a temp table, but might as well get it right.)
>
> The xlog action here of copying a page image is currently
> btree-specific, but maybe we should move it to a more widely visible
> place, such as heapam.c.  I don't see any value in having identical
> xlog recovery actions in several different modules.

I was just thinking that. I imagine that this would be useful for WAL
logging of createdb() when that functionality gets implemented.

We might also be able to use it as a speed up for cluster() (some time
in the future). That is, we could form a complete page in memory in
relation_rebuild() and then write it out directly.

Gavin