Horton

Re: Option to not use ringbuffer in VACUUM, using it in failsafe mode

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Robert Haas <robertmhaas@gmail.com>, Melanie Plageman <melanieplageman@gmail.com>, David Rowley <dgrowleyml@gmail.com>
Date: 2023-01-11T19:06:26Z
Lists: pgsql-hackers 
On Wed, Jan 11, 2023 at 10:58 AM Andres Freund <andres@anarazel.de> wrote:
> Any idea about the name? The obvious thing is to reference ring buffers in the
> option name, but that's more of an implementation detail...

What are the chances that anybody using this feature via a manual
VACUUM command will also use INDEX_CLEANUP off? It's not really
supposed to be used routinely, at all. Right? It's just for
emergencies.

Perhaps it can be tied to INDEX_CLEANUP=off? That makes it hard to get
just the behavior you want when testing VACUUM, but maybe that doesn't
matter.

Realistically, most of the value here comes from changing the failsafe
behavior, which doesn't require the user to know anything about
VACUUM. I know that AWS has reduced the vacuum_failsafe_age default on
RDS to 1.2 billion (a decision made before I joined Amazon), so it is
already something AWS lean on quite a bit where available.

-- 
Peter Geoghegan

Commits

  1. Add unit to vacuum_buffer_usage_limit value in postgresql.conf.sample.

  2. Improve VACUUM/ANALYZE BUFFER_USAGE_LIMIT docs

  3. Add --buffer-usage-limit option to vacuumdb

  4. Add VACUUM/ANALYZE BUFFER_USAGE_LIMIT option

  5. Move various prechecks from vacuum() into ExecVacuum()

  6. Always make a BufferAccessStrategy for ANALYZE

  7. Rename BufferAccessStrategyData.ring_size to nbuffers

  8. Disable vacuum's use of a buffer access strategy during failsafe

  9. Only make buffer strategy for vacuum when it's likely needed

  10. Remove some global variables from vacuum.c

  11. Doc: add Buffer Access Strategy to the glossary