Horton

Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access)

Melanie Plageman <melanieplageman@gmail.com>

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From: Melanie Plageman <melanieplageman@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Kirill Reshke <reshkekirill@gmail.com>, Andrey Borodin <x4mmm@yandex-team.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2025-10-08T22:54:25Z
Lists: pgsql-hackers

Commits

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

  1. Remove table_scan_analyze_next_tuple unneeded parameter OldestXmin

  2. Simplify visibility check in heap_page_would_be_all_visible()

  3. Eliminate use of cached VM value in lazy_scan_prune()

  4. Combine visibilitymap_set() cases in lazy_scan_prune()

  5. Fix const qualification in prune_freeze_setup()

  6. Simplify vacuum visibility assertion

  7. Split heap_page_prune_and_freeze() into helpers

  8. Assert that cutoffs are provided if freezing will be attempted

  9. Split PruneFreezeParams initializers to one field per line

  10. Refactor heap_page_prune_and_freeze() parameters into a struct

  11. Make heap_page_is_all_visible independent of LVRelState

  12. Inline TransactionIdFollows/Precedes[OrEquals]()

  13. Add helper for freeze determination to heap_page_prune_and_freeze

  14. Bump XLOG_PAGE_MAGIC after xl_heap_prune change

  15. Correct prune WAL record opcode name in comment

  16. Add error codes when vacuum discovers VM corruption

  17. Remove unused xl_heap_prune member, reason

  18. Remove unneeded VM pin from VM replay

  19. Add assert and log message to visibilitymap_set

  20. Add error codes to some corruption log messages

Attachments

On Mon, Oct 6, 2025 at 6:40 PM Melanie Plageman
<melanieplageman@gmail.com> wrote:
>
> In attached v16, I’ve reverted to removing XLOG_HEAP2_VISIBLE
> entirely, rather than first removing each caller's heap page from the
> VM WAL chain. I reordered changes and squashed several refactoring
> patches to improve patch-by-patch readability. This should make the
> set read differently from earlier versions that removed
> XLOG_HEAP2_VISIBLE and had more step-by-step mechanical refactoring.
>
> I think if we plan to go all the way with removing XLOG_HEAP2_VISIBLE,
> having intermediate patches that just set PD_ALL_VISIBLE when making
> other heap pages are more confusing than helpful. Also, I think having
> separate flags for setting PD_ALL_VISIBLE in the WAL record
> over-complicated the code.

I decided to reorder the patches to remove XLOG_HEAP2_VISIBLE from
vacuum phase III before removing it from vacuum phase I because
removing it from phase III doesn't require preliminary refactoring
patches. I've done that in the attached v17.

I've also added an experimental patch on the end that refactors large
chunks of heap_page_prune_and_freeze() into helpers. I got some
feedback off-list that heap_page_prune_and_freeze() is too unwieldy
now. I'm not sure how I feel about them yet, so I haven't documented
them or moved them up in the patch set to before changes to
heap_page_prune_and_freeze().

0001: Eliminate XLOG_HEAP2_VISIBLE from COPY FREEZE
0002: Eliminate XLOG_HEAP2_VISIBLE from phase III of vacuum
0003 - 0006: cleanup and refactoring to prepare for 0007
0007: Eliminate XLOG_HEAP2_VISIBLE from vacuum prune/freeze
0008 - 0009: Remove XLOG_HEAP2_VISIBLE
0010 - 0012: refactoring to prepare for 0013
0013: Set VM on-access
0014: Set pd_prune_xid on insert
0015: Experimental refactoring of heap_page_prune_and_freeze into helpers

- Melanie