On Wed, Feb 29, 2012 at 5:52 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Wed, Feb 29, 2012 at 4:34 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> Easier for who? I don't care for the idea of code that has to cope with
>>> two page formats, or before long N page formats, because if we don't
>>> have some mechanism like this then we will never be able to decide that
>>> an old data format is safely dead.
>
>> Huh? You can drop support for a new page format any time you like.
>> You just decree that version X+1 no longer supports it, and you can't
>> pg_upgrade to it until all traces of the old page format are gone.
>
> And how would a DBA know that?
We'd add a column to pg_class that tracks which page version is in use
for each relation.
--
Robert Haas
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