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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: Alexander Lakhin <exclusion@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Tomas Vondra <tomas@vondra.me>, David Rowley <dgrowleyml@gmail.com>, Kirill Reshke <reshkekirill@gmail.com>, Chao Li <li.evan.chao@gmail.com>, 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: 2026-04-20T20:28:03Z
Lists: pgsql-hackers 
On Mon, Apr 20, 2026 at 3:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
>
> I think, I found another test which suffers from autoanalyze with the new
> behavior: [1], [2].

Thanks for continuing to look for these!

> Initially I reproduced this diff on a slow armv7 device after many
> iterations of `make check` with:
> autovacuum_naptime = 1
> autovacuum_analyze_threshold = 1
> debug_parallel_query = 'regress'
>
> But now I see that it can be reproduced on an ordinary machine with just:
> --- a/src/test/regress/sql/plancache.sql
> +++ b/src/test/regress/sql/plancache.sql
> @@ -208,2 +208,3 @@ execute test_mode_pp(1); -- 2x
>  execute test_mode_pp(1); -- 3x
> +analyze test_mode;
>  execute test_mode_pp(1); -- 4x
> (and expected/plancache.out updated)
>
> and `make check` running in a loop. It failed for me on iterations 5, 4,
> 10 (as far as I can see, analyze updates relallvisible not every time):

If you do vacuum test_mode instead, it should fail reliably.

I think we can avoid having relallvisible updated by doing two things:
1) moving the analyze test_mode above the create index because the
create index will scan the table and could set pages all-visible and
then the analyze may update the statistics
2) create the table with autovacuum_enabled = false to avoid vacuum
and analyze running after any of the other table scans may set some
pages all-visible

- 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