Re: WORM and Read Only Tables (v0.1)

On Sat, 2007-12-15 at 13:32 +0100, Albert Cervera i Areny wrote:
> > Read-Only Tables
> > ----------------
> > Postgres supports the concept of freezing tuples, so they can live
> > forever within the database without needing further writes. Currently
> > there is no command that will guarantee that a table has been completely
> > frozen. This makes it difficult to reliably write data files to WORM
> > media for longer term archiving. (WORM means Write-Once, Read-Many).
> > It's also a pain having to VACUUM a large table again just because a
> > small number of rows need to be frozen.
> >
>
> I'm not an expert at all, but I'd like to understand this, do you plan that
> READ-ONLY tables wouldn't even store transaction information? That should
> save quite a lot of space. Maybe when the table would be moved to the
> compressed tablespace, MVCC information could be dropped too? Of course that
> would avoid future insert & update possibilities though.

It could, but its a lot of work for little gain. The tuple headers look
like they will compress fairly well, so why bother to remove them at
all?

--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com