Re: foreign key locks, 2nd attempt

On 16.01.2012 21:52, Alvaro Herrera wrote:
>
> Excerpts from Heikki Linnakangas's message of lun ene 16 16:17:42 -0300 2012:
>>
>> On 15.01.2012 06:49, Alvaro Herrera wrote:
>>> - pg_upgrade bits are missing.
>>
>> I guess we'll need to rewrite pg_multixact contents in pg_upgrade. Is
>> the page format backwards-compatible?
>
> It's not.
>
> I haven't worked out what pg_upgrade needs to do, honestly.  I think we
> should just not copy old pg_multixact files when upgrading across this
> patch.

Sorry, I meant whether the *data* page format is backwards-compatible? 
the multixact page format clearly isn't.

>  I was initially thinking that pg_multixact should return the
> empty set if requested members of a multi that preceded the freeze
> point.  That way, I thought, we would just never try to access a page
> originated in the older version (assuming the freeze point is set to
> "current" whenever pg_upgrade runs).  However, as things currently
> stand, accessing an old multi raises an error.  So maybe we need a
> scheme a bit more complex to handle this.

Hmm, could we create new multixact files filled with zeros, covering the 
range that was valid in the old cluster?

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