Re: preserving db/ts/relfilenode OIDs across pg_upgrade (was Re: storing an explicit nonce)

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Shruthi Gowda <gowdashru(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Kincaid <tomjohnkincaid(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>
Subject: Re: preserving db/ts/relfilenode OIDs across pg_upgrade (was Re: storing an explicit nonce)
Date: 2021-08-26 17:34:48
Message-ID: 20210826173448.GJ22637@momjian.us
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On Thu, Aug 26, 2021 at 01:20:38PM -0400, Robert Haas wrote:
> So I think this proposed change is in the safe direction. If
> relfilenodes were currently preserved and we wanted to make them not
> be preserved, then I think you would be quite right to say "whoa,
> whoa, that could be a problem." Indeed it could. If anyone then in the
> future wanted to introduce a dependency on them staying the same, they
> would have a problem. However, nothing in the server itself can care
> about relfilenodes - or anything else - being *different* across a
> pg_upgrade. The whole point of pg_upgrade is to make it feel like you
> have the same database after you run it as you did before you ran it,
> even though under the hood a lot of surgery has been done. Barring
> bugs, you can never be sad about there being too LITTLE difference
> between the post-upgrade database and the pre-upgrade database.

Yes, this makes sense, and it is good we have stated the possible
benefits now:

* pgBackRest
* pg_upgrade diagnostics
* TDE (maybe)

We can eventually evaluate the value of this based on those items.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

If only the physical world exists, free will is an illusion.

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