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

On 2019-Apr-30, John Naylor wrote:

> On Fri, Apr 26, 2019 at 11:52 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)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.

Hmm ... so, if vacuum runs and frees up any space from any of the pages,
then it should send out an invalidation -- it doesn't matter what the
FSM had, just that there is more free space now. That means every other
process will need to determine a fresh FSM, but that seems correct.
Sounds better than keeping outdated entries indicating no-space-available.

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Álvaro Herrera https://www.2ndQuadrant.com/
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