Re: Emit fewer vacuum records by reaping removable tuples during pruning

Melanie Plageman <melanieplageman@gmail.com>

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From: Melanie Plageman <melanieplageman@gmail.com>

To: Pg Hackers <pgsql-hackers@postgresql.org>

Cc: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Peter Geoghegan <pg@bowt.ie>

Date: 2023-11-17T23:12:08Z

Lists: pgsql-hackers

Attachments

v2-0002-Set-would-be-dead-items-LP_UNUSED-while-pruning.patch (text/x-patch) patch v2-0002
v2-0001-Indicate-rel-truncation-unsafe-in-lazy_scan-no-pr.patch (text/x-patch) patch v2-0001

On Mon, Nov 13, 2023 at 5:28 PM Melanie Plageman
<melanieplageman@gmail.com> wrote:
> When there are no indexes on the relation, we can set would-be dead
> items LP_UNUSED and remove them during pruning. This saves us a vacuum
> WAL record, reducing WAL volume (and time spent writing and syncing
> WAL).
...
> Note that (on principle) this patch set is on top of the bug fix I
> proposed in [1].
>
> [1] https://www.postgresql.org/message-id/CAAKRu_YiL%3D44GvGnt1dpYouDSSoV7wzxVoXs8m3p311rp-TVQQ%40mail.gmail.com

Rebased on top of fix in b2e237afddc56a and registered for the january fest
https://commitfest.postgresql.org/46/4665/

- Melanie

Commits

Combine FSM updates for prune and no-prune cases.
- 5eafacd2797d 17.0 landed
Remove LVPagePruneState.
- e313a6113704 17.0 landed
Move VM update code from lazy_scan_heap() to lazy_scan_prune().
- cb970240f13d 17.0 landed
Optimize vacuuming of relations with no indexes.
- c120550edb86 17.0 landed
Be more consistent about whether to update the FSM while vacuuming.
- 45d395cd75ff 17.0 landed
Remove hastup from LVPagePruneState.
- e2d5b3b9b643 17.0 landed
Use scanned_pages to decide when to failsafe check.
- 07eef53955ea 16.0 cited
Simplify lazy_scan_heap's handling of scanned pages.
- 44fa84881fff 15.0 cited
While vacuuming a large table, update upper-level FSM data every so often.
- 851a26e26637 11.0 cited