Horton

Re: Unhappy about API changes in the no-fsm-for-small-rels patch

John Naylor <john.naylor@2ndquadrant.com>

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From: John Naylor <john.naylor@2ndquadrant.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-04-30T06:12:11Z
Lists: pgsql-hackers

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On Fri, Apr 26, 2019 at 11:52 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> As discussed above, we need to issue an
> invalidation for following points:  (a) when vacuum finds there is no
> FSM and page has more space now, I think you can detect this in
> RecordPageWithFreeSpace

I took a brief look and we'd have to know how much space was there
before. That doesn't seem possible without first implementing the idea
to save free space locally in the same way the FSM does. Even if we
have consensus on that, there's no code for it, and we're running out
of time.

> (b) invalidation to notify the existence of
> FSM, this can be done both by vacuum and backend.

I still don't claim to be anything but naive in this area, but does
the attached get us any closer?

-- 
John Naylor                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Revert "Avoid the creation of the free space map for small heap relations".

  2. Improve code comments in b0eaa4c51b.

  3. During pg_upgrade, conditionally skip transfer of FSMs.

  4. Add more tests for FSM.

  5. Fix typos in commit 8586bf7ed8.

  6. tableam: introduce table AM infrastructure.

  7. Clear the local map when not used.

  8. Doc: Update the documentation for FSM behavior for small tables.

  9. Make FSM test portable.

  10. Avoid creation of the free space map for small heap relations, take 2.