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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: Kirill Reshke <reshkekirill@gmail.com>
Cc: Chao Li <li.evan.chao@gmail.com>, Andres Freund <andres@anarazel.de>, Andrey Borodin <x4mmm@yandex-team.ru>, Xuneng Zhou <xunengzhou@gmail.com>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2026-03-17T14:48:55Z
Lists: pgsql-hackers

Attachments

On Tue, Mar 17, 2026 at 5:05 AM Kirill Reshke <reshkekirill@gmail.com> wrote:
>
> > From 788860ded375fcf744201347b9dcbf496070bfb5 Mon Sep 17 00:00:00 2001
> > From: Melanie Plageman <melanieplageman@gmail.com>
> > Date: Wed, 25 Feb 2026 16:48:19 -0500
> > Subject: [PATCH v39 02/12] Add pruning fast path for all-visible and
>  all-frozen pages
>
> For the record, does this work with DISABLE_PAGE_SKIPPING? I think we
> don't  want the server to "fast-path" in case this option is set by
> the user...

Hmm. This is a good point. The docs for DISABLE_PAGE_SKIPPING say it
is about fixing visibility map corruption and the fast path does
detect and fix one type of visibility map corruption. It does not
investigate for dead line pointers, though. I suppose
DISABLE_PAGE_SKIPPING would want to also do that kind of VM corruption
detection. Thanks for thinking of that. Attached v40 adds an option to
disable the fast path.

- Melanie

Commits

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

  1. Stabilize btree_gist test against on-access VM setting

  2. Stabilize plancache test against on-access VM setting

  3. Make local buffers pin limit more conservative

  4. Update FSM during prune/freeze replay even if freespace is zero

  5. Pass down information on table modification to scan nodes

  6. Thread flags through begin-scan APIs

  7. Remove PlannedStmt->resultRelations in favor of resultRelationRelids

  8. Make it cheap to check if a relation is modified by a query

  9. Keep newest live XID up-to-date even if page not all-visible

  10. Add pruning fast path for all-visible and all-frozen pages

  11. Detect and fix visibility map corruption in more cases

  12. Save vmbuffer in heap-specific scan descriptors for on-access pruning

  13. Avoid BufferGetPage() calls in heap_update()

  14. Initialize missing fields in CreateExecutorState()

  15. Prefix PruneState->all_{visible,frozen} with set_

  16. Add PageGetPruneXid() helper

  17. Move commonly used context into PruneState and simplify helpers

  18. Remove table_scan_analyze_next_tuple unneeded parameter OldestXmin

  19. Simplify visibility check in heap_page_would_be_all_visible()

  20. Rename LVRelState VM-related logging counters

  21. Fix flakiness in the pg_visibility VM-only vacuum test by using a temporary table.

  22. Refactor lazy_scan_prune() VM clear logic into helper

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

  24. Combine visibilitymap_set() cases in lazy_scan_prune()

  25. Fix const qualification in prune_freeze_setup()

  26. Simplify vacuum visibility assertion

  27. Split heap_page_prune_and_freeze() into helpers

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

  29. Split PruneFreezeParams initializers to one field per line

  30. Refactor heap_page_prune_and_freeze() parameters into a struct

  31. Make heap_page_is_all_visible independent of LVRelState

  32. Inline TransactionIdFollows/Precedes[OrEquals]()

  33. Add helper for freeze determination to heap_page_prune_and_freeze

  34. Bump XLOG_PAGE_MAGIC after xl_heap_prune change

  35. Correct prune WAL record opcode name in comment

  36. Add error codes when vacuum discovers VM corruption

  37. Remove unused xl_heap_prune member, reason

  38. Remove unneeded VM pin from VM replay

  39. Add assert and log message to visibilitymap_set

  40. Stamp HEAD as 19devel.

  41. Add error codes to some corruption log messages