Horton

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

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Stephen Frost <sfrost@snowman.net>, Shruthi Gowda <gowdashru@gmail.com>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Masahiko Sawada <sawada.mshk@gmail.com>, Tom Kincaid <tomjohnkincaid@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Development <pgsql-hackers@postgresql.org>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2021-08-24T18:49:00Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Rethink method for assigning OIDs to the template0 and postgres DBs.

  2. pg_upgrade: Preserve database OIDs.

  3. pg_upgrade: Preserve relfilenodes and tablespace OIDs.

  4. Fix for new Boolean node

  5. Improve error handling of HMAC computations

  6. Add macro RelationIsPermanent() to report relation permanence

  7. Enhance nbtree index tuple deletion.

On Tue, Aug 24, 2021 at 02:34:26PM -0400, Robert Haas wrote:
> On Tue, Aug 24, 2021 at 2:16 PM Bruce Momjian <bruce@momjian.us> wrote:
> > One other issue --- the more that pg_upgrade preserves, the more likely
> > pg_upgrade will break when some internal changes happen in Postgres.
> > Therefore, if you want pg_upgrade to preserve something, you have to
> > have a good reason --- even code simplicity might not be a sufficient
> > reason.
> 
> While I accept that as a general principle, I don't think it's really
> applicable in this case. pg_upgrade already knows all about
> relfilenodes; it has a source file called relfilenode.c. I don't see
> that a pg_upgrade that preserves relfilenodes is any more or less
> likely to break in the future than a pg_upgrade that renumbers all the
> files so that the relation OID and the relfilenode are equal. You've
> got about the same amount of reliance on the on-disk layout either
> way.

I was making more of a general statement that preservation can be
problematic and its impact must be researched.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

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