Re: [WIP] In-place upgrade

"Robert Haas" <robertmhaas(at)gmail(dot)com> writes:

>>> Maybe. The difference is that I'm talking about converting tuples,
>>> not pages, so "What happens when the data doesn't fit on the new
>>> page?" is a meaningless question.
>>
>> No it's not, because as you pointed out you still need a way for the user to
>> force it to happen sometime. Unless you're going to be happy with telling
>> users they need to update all their tuples which would not be an online
>> process.
>>
>> In any case it sounds like you're saying you want to allow multiple versions
>> of tuples on the same page -- which a) would be much harder and b) doesn't
>> solve the problem since the page still has to be converted sometime anyways.
>
> No, that's not what I'm suggesting. My thought was that any V3 page
> would be treated as if it were completely full, with the exception of
> a completely empty page which can be reinitialized as a V4 page. So
> you would never add any tuples to a V3 page, but you would need to
> update xmax, hint bits, etc. Eventually when all the tuples were dead
> you could reuse the page.

But there's no guarantee that will ever happen. Heikki claimed you would need
a mechanism to convert the page some day and you said you proposed a system
where that wasn't true.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's Slony Replication support!