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Re: Database file compatability

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: Database file compatability
Date: 2005-09-27 15:59:52
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Lists: pgsql-hackers
On Mon, Sep 26, 2005 at 07:05:28PM -0400, Tom Lane wrote:
> "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu> writes:
> > ""Jim C. Nasby"" <jnasby(at)pervasive(dot)com> wrote
> >> If a database is created with a 64 bit version of initdb, would a 32bit
> >> backend be able to talk to it? Likewise, would a backend compiled by a
> >> different compiler be able to?
> > The key problem I believe is the serials of ALIGNOF macros. Especially for 
> > MAX_ALIGNOF. Different Hardware/OS/compiler will have different 
> > understanding of it.
> Yeah.  It might be worth adding MAX_ALIGNOF to the set of configuration
> data stored in pg_control, just to be sure you couldn't shoot yourself
> in the foot that way.


ISTM that 64 bit is becomming much more common, so I think the odds of
someone going from a 32 to 64 bit (or vice-versa) version of PostgreSQL
on the same machine is much larger now than it has been in the past. I
think we really need to protect this as much as possible. This isn't so
much a foot-gun as a foot-nuclear-weapon.

Would I be correct in assuming that doing this for 8.1 would require
another initdb? :/ For something as minor as this, would it be
reasonable to ship a utility to avoid the initdb? I'd very much like to
see this in 8.1...
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software    work: 512-231-6117
vcard:       cell: 512-569-9461

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