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

Kirill Reshke <reshkekirill@gmail.com>

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From: Kirill Reshke <reshkekirill@gmail.com>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Chao Li <li.evan.chao@gmail.com>, Xuneng Zhou <xunengzhou@gmail.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Andrey Borodin <x4mmm@yandex-team.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2026-01-03T21:36:25Z
Lists: pgsql-hackers 
On Tue, 23 Dec 2025 at 06:18, Melanie Plageman
<melanieplageman@gmail.com> wrote:
>
> Right, it is totally okay to change function APIs in a major release.
> My point was not that it wasn't allowed but that if people are getting
> useful information returned from that function, or if we think we
> might want that information again in the future, we should think twice
> before changing it. But, in this case, I think we don't need to worry
> about it.
>
> - Melanie

At first glance this change looks sane, and I do not find any reason why
table_scan_analyze_next_tuple needs knowledge about OldestXid. But I am not
aware of this function design discussions, maybe OldestXid is here for
a good reason.

After thinking about it for a week or so, I would actually suggest
moving forward with v31 (Remove OldestXmin from TAM).
I think this is a low probability of getting complaints about that.
Also, we're breaking ABI, so we will know about any important use-case
not long after 19-beta1.
Another user of extensible TAM, Cloudberry [0], does not use
OldestXmin also. I also did not find any user of
scan_analyze_next_tuple other than postgresql itself with
http://codesearch.decbian.net/ . Using code-search on github I found
[1]. Looks like this does not need OldestXmin either.

[0] https://github.com/apache/cloudberry
[1] https://github.com/hydradatabase/columnar/blob/main/columnar/src/backend/columnar/columnar_tableam.c#L2080C68-L2080C78

--
Best regards,
Kirill Reshke

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