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
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