On 07/31/2015 09:22 AM, Gurjeet Singh wrote:
On Jul 30, 2015 2:23 PM, "Tom Lane" <t...@sss.pgh.pa.us> wrote:
But the elephant in the room is on-disk compatibility. There is
absolutely no way that we can just change xmin/xmax to 64 bits without a
disk format break. However, if we do something like what Heikki is
suggesting, it's at least conceivable that we could convert incrementally
(ie, if you find a page with the old header format, assume all tuples in
it are part of epoch 0; and do not insert new tuples into it unless there
is room to convert the header to new format ... but I'm not sure what we
do about tuple deletion if the old page is totally full and we need to
write an xmax that's past 4G).
Can we safely relegate the responsibility of tracking the per block epoch
to a relation fork?
Sounds complicated and fragile. I would rather attack the page version
problem head on.
- Heikki
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