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Re: New IndexAM API controlling index vacuum strategies

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Masahiko Sawada <sawada.mshk@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Noah Misch <noah@leadboat.com>
Date: 2021-04-15T00:20:06Z
Lists: pgsql-hackers 
On Wed, Apr 14, 2021 at 5:08 PM Robert Haas <robertmhaas@gmail.com> wrote:
> I think this is largely missing the point Andres was making, which is
> that you made a significant behavior change after feature freeze
> without any real opportunity for discussion.

I don't believe that it was a significant behavior change, for the
reason I gave: the fact of the matter is that it's practically
impossible for us to truncate the heap anyway, provided we have
already decided to not vacuum (as opposed to prune) heap pages that
almost certainly have some LP_DEAD items in them. Note that later heap
pages are the most likely to still have some LP_DEAD items once the
failsafe triggers, which are precisely the ones that will affect
whether or not we can truncate the whole heap.

I accept that I could have done better with the messaging. I'll try to
avoid repeating that mistake in the future.

> More generally, you've
> changed a bunch of other stuff relatively quickly based on input from
> a relatively limited number of people. Now, it's fair to say that it's
> often hard to get input on things, and sometimes you have to just take
> your best shot and hope you're right.

I agree in general, and I agree that that's what I've done in this
instance. It goes without saying, but I'll say it anyway: I accept
full responsibility.

> But in this particular case, you
> didn't even try to get broader participation or buy-in. That's not
> good.

I will admit to being somewhat burned out by this project. That might
have been a factor.

-- 
Peter Geoghegan

Commits

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

  1. Don't truncate heap when VACUUM's failsafe is in effect.

  2. Teach VACUUM to bypass unnecessary index vacuuming.

  3. Add wraparound failsafe to VACUUM.

  4. Truncate line pointer array during VACUUM.

  5. Remove tupgone special case from vacuumlazy.c.

  6. Refactor lazy_scan_heap() loop.

  7. Propagate parallel VACUUM's buffer access strategy.

  8. Simplify state managed by VACUUM.

  9. Notice that heap page has dead items during VACUUM.

  10. Adjust lazy_scan_heap() accounting comments.

  11. Use full 64-bit XID for checking if a deleted GiST page is old enough.

  12. Fix some problems with VACUUM (INDEX_CLEANUP FALSE).