Horton

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

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

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Amit Kapila <amit.kapila16@gmail.com>, John Naylor <john.naylor@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-04-23T17:31:25Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2019-04-23 15:46:17 +0530, Amit Kapila wrote:
>> If we invalidate it only when there's no space on the page, then when
>> should we set it back to available, because if we don't do that, then
>> we might miss the space due to concurrent deletes.

> Well, deletes don't traditionally (i.e. with an actual FSM) mark free
> space as available (for heap). I think RecordPageWithFreeSpace() should
> issue a invalidation if there's no FSM, and the block goes from full to
> empty (as there's no half-full IIUC).

Why wouldn't we implement this just as a mini four-entry FSM stored in
the relcache, and update the entries according to the same rules we'd
use for regular FSM entries?

			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.