Re: [WIP] In-place upgrade

Greg Stark napsal(a):
> I don't think this really qualifies as "in place upgrade" since it would 
> mean creating a whole second copy of all your data. And it's only online 
> got read-only queries too.
> 
> I think we need a way to upgrade the pages in place and deal with any 
> overflow data as exceptional cases or else there's hardly much point in 
> the exercise.

It is exceptional case between V3 and V4 and only on heap, because you save in 
varlena. But between V4 and V5 we will lost another 4 bytes in a page header -> 
page header will be 28 bytes long but tuple size is same.

Try to get raw free space on each page in 8.3 database and you probably see a 
lot of pages where free space is 0. My last experience is something about 1-2% 
of pages.
    Zdenek