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

Melanie Plageman <melanieplageman@gmail.com>

From: Melanie Plageman <melanieplageman@gmail.com>

To: Robert Haas <robertmhaas@gmail.com>

Cc: Michael Paquier <michael@paquier.xyz>, Peter Geoghegan <pg@bowt.ie>, Pg Hackers <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>

Date: 2024-01-05T20:34:22Z

Lists: pgsql-hackers

Attachments

v3-0004-Inline-LVPagePruneState-members-in-lazy_scan_prun.patch (text/x-patch) patch v3-0004
v3-0001-Indicate-rel-truncation-unsafe-in-lazy_scan-no-pr.patch (text/x-patch) patch v3-0001
v3-0003-Update-VM-in-lazy_scan_prune.patch (text/x-patch) patch v3-0003
v3-0002-Set-would-be-dead-items-LP_UNUSED-while-pruning.patch (text/x-patch) patch v3-0002
v3-0005-Remove-unneeded-struct-LVPagePruneState.patch (text/x-patch) patch v3-0005
v3-0006-Conslidate-FSM-update-code-in-lazy_scan_heap.patch (text/x-patch) patch v3-0006

On Fri, Jan 5, 2024 at 1:47 PM Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Fri, Jan 5, 2024 at 12:59 PM Melanie Plageman
> <melanieplageman@gmail.com> wrote:
> MP> I am planning to add a VM update into the freeze record, at which point
> MP> I will move the VM update code into lazy_scan_prune(). This will then
> MP> allow us to consolidate the freespace map update code for the prune and
> MP> noprune cases and make lazy_scan_heap() short and sweet.
>
> Can we see what that looks like on top of this change?

Yes, attached is a patch set which does this. My previous patchset
already reduced the number of places we unlock the buffer and update
the freespace map in lazy_scan_heap(). This patchset combines the
lazy_scan_prune() and lazy_scan_noprune() FSM update cases. I also
have a version which moves the freespace map updates into
lazy_scan_prune() and lazy_scan_noprune() -- eliminating all of these
from lazy_scan_heap(). This is arguably more clear. But Andres
mentioned he wanted fewer places unlocking the buffer and updating the
FSM.

- 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