Re: pg_upgrade project status

Zdenek Kotala wrote:
> Bruce Momjian napsal(a):
> > Zdenek Kotala wrote:
> >> In the last week community made decision about pg_upgrade project and its 
> >> implementation. I would like to try summarize this conclusion and I add other 
> >> topic which should be finished for 8.4.
> >>
> >> Convert on read has been selected as a good way, because it is not invasive and 
> >> does not limit fresh database. But, this way needs core modification which 
> >> allows to do online in-place upgrade. It means no online in-place upgrade to 8.4 
> >> will be implemented. Sorry about that, but we need move forward and there is not 
> >> easy way without core modification to do it.
> >>
> >> As I mentioned manytimes before there are two major issues with convert on read 
> >> and one small issue.
> >>
> >> 1) Data does not fit on the new page. It will be solve by pre-upgrade check 
> >> which reserve space on each page, before upgrade.
> > 
> > Rather than specifying free space as an amount, I was thinking of having
> > a boolean like 'ready_for_upgrade' and the system internally would know
> > how much free space for each page and tuple.
> 
> You need booth, flag which shows you that the relation/database is ready for 
> upgrade and free space reservation configuration for each column. System cannot 
> know it because PostgreSQL is not oracle :-). It does not know what will happend 
> during next version development :-). It have to be setup by pre-upgrade script.

So every Postgres version will allow space reservation based on the
table and page, and the pre-upgrade script will set those values based
on the table's columns --- makes sense, and avoids the need for a minor
update to Postgres to add new code --- good idea.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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