Re: pg_upgrade project status

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.

    Zdenek