Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Amit Kapila <amit.kapila16@gmail.com>, John Naylor <john.naylor@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-05-06T16:05:21Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> ... I guess you could incur the overhead repeatedly if the relation starts
> out at 1 block, grows to 4, is vacuumed back down to 1, lather, rinse,
> repeat, but is that actually realistic?

While I've not studied the patch, I assumed that once a relation has an
FSM it won't disappear.  Making it go away again if the relation gets
shorter seems both fairly useless and a promising source of bugs.

			regards, tom lane

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.