Re: WAL page magic number (was Re: Re: [COMMITTERS] pgsql: Make CheckRequiredParameterValues() depend upon correct)

Bruce Momjian wrote:
> Heikki Linnakangas wrote:
>> Tom Lane wrote:
>>> Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>>>> Browsing the history of XLOG_PAGE_MAGIC, it used to be incremented by
>>>> one whenever the format changes, at least as long as it has been been in
>>>> xlog_internal.h. It started at 0xD05B in 2005, and was incremented by
>>>> one by each commit till 0xD062. But then the hot standby patch bumped it
>>>> to 0xD166, and on March 19th Simon changed it to 0x9002, and on March
>>>> 28th to 0x9003.
>>>> Is there a plan somewhere on all that, or was it just random whacking?
>>> Random whacking. Simon seems to have decided to try to make the number
>>> mean something, but it never meant anything before. It's not a version
>>> number, it's a magic identifier. We might need to avoid certain values
>>> to prevent collisions with other file formats, so I'm suspicious of
>>> trying to make it match up with some expectation.
>> Ok, for better or worse, I whacked it back to the old series.
>
> Agreed. Making it match the version would be odd because you then have
> t bump it for every major release.

Not necessarily. It would make sense to me to just keep it the same if
there has been no changes. The magic number would indicate the first
version that used that format.

I'm not advocating a switch to that system, but it would be sensible as
well.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com