On Tue, Jun 9, 2009 at 10:10 AM, Roland Hughes
<roland@logikalsolutions.com> wrote:
On Tuesday 09 June 2009 08:55:18 am Tino Schwarze wrote:
>
> You just need to preserve everything from Postgres' data directory
> (which shouldn't be much data).
>
While it shouldn't be much data, it is also non-robust. With robust databases, you can create as many databases as you want in as many places as you want. A "fresh install" means that you only have to "tell" the database monitor about those places again. Everything is still there and usable.
It's really sad that PostgreSQL doesn't have an ADD TABLESPACE command or the functionality built into CREATE TABLESPACE to recognize a tablespace already exists and simply recreate the entry for it in the default tablespace. When one creates an entire database in this new tablespace, PostgreSQL should need nothing other than to know the tablespace exists as everything else should be stored in that tablespace.
Now now :-) In all fairness, even something like Oracle (I think one could argue that the industry considers this a 'robust' database) needs certain metadata available to import a tablespace from another instance -- i.e. you have to export metadata, and if you lost the first instance before you do that but save a tablespace, you'd be in the same predicament.
A fairly important concept in the Oracle world is protection of a control file, in postgres, you really need to preserve control structures like the pg_clog, the control file, etc... Personally, I don't know anything about RDB, but I would venture a guess that you're going to encounter restrictions there as well.
--Scott
