Re: Proposal: Multiversion page api (inplace upgrade)

Heikki Linnakangas napsal(a):
> Zdenek Kotala wrote:
>> 4) Implementation
>>
>> The main point of implementation is to have several version of 
>> PageHeader structure (e.g. PageHeader_04, PageHeader_03 ...) and 
>> correct structure will be handled in special branch (see examples).
> 
> (this won't come as a surprise as we talked about this in PGCon, but) I 
> think we should rather convert the page structure to new format in 
> ReadBuffer the first time a page is read in. That would keep the changes 
> a lot more isolated.

I agree with Tom's reply. And anyway this approach will be mostly isolated into 
page.c and you need to able read old page in both cases.

> Note that you need to handle not only page header changes, but changes 
> to internal representations of different data types, and changes like 
> varvarlen and combocid. Those are things that have happened in the past; 
> in the future, I'm foreseeing changes to the toast header, for example, 
> as there's been a lot of ideas related to toast options compression.

I know, this is a first small step for inplace upgrade. Tupleheader will follow. 
Page structure is basic. I want to split development into small steps, because 
it is easy to review.
     Zdenek