Horton

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

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Peter Geoghegan <pg@bowt.ie>, pgsql-hackers@postgresql.org, Robert Haas <robertmhaas@gmail.com>
Date: 2023-04-06T01:14:47Z
Lists: pgsql-hackers 
On Thu, 6 Apr 2023 at 12:42, Melanie Plageman <melanieplageman@gmail.com> wrote:
> Attached is a v12 of the whole vacuum_buffer_usage_limit patch set which
> includes a commit to fix the bug in master and a commit to move relevant
> code from vacuum() up into ExecVacuum().

I'm still playing catch up to the moving of the pre-checks from
vacuum() to ExecVacuum().  I'm now wondering...

Is it intended that VACUUM t1,t2; now share the same strategy?
Currently, in master, we'll allocate a new strategy for t2 after
vacuuming t1. Does this not mean we'll now leave fewer t1 pages in
shared_buffers because the reuse of the strategy will force them out
with t2 pages?  I understand there's nothing particularly invalid
about that, but it is a change in behaviour that the patch seems to be
making with very little consideration as to if it's better or worse.

David

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