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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: Andrey Borodin <x4mmm@yandex-team.ru>
Cc: Kirill Reshke <reshkekirill@gmail.com>, Chao Li <li.evan.chao@gmail.com>, Xuneng Zhou <xunengzhou@gmail.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2026-01-06T17:31:57Z
Lists: pgsql-hackers

Attachments

On Tue, Jan 6, 2026 at 4:40 AM Andrey Borodin <x4mmm@yandex-team.ru> wrote:
>
> > <v32-0014-Pass-down-information-on-table-modification-to-s.patch>
>
> I've tried to take an attempt to review some patches of this patchset. It's huge and mostly polished.

I've added attributed your review on the patches you specifically
mention here (and from previous emails you sent). Let me know if there
are other patches you reviewed that you did not mention.

> In a step "Pass down information on table modification to scan node" you pass SO_HINT_REL_READ_ONLY flag in IndexNext() and BitmapTableScanSetup(), but not in IndexNextWithReorder() and IndexOnlyNext(). Is there a reason why index scans with ordering cannot use on-access VM setting?

Great point, I simply hadn't tested those cases and didn't think to
add them. I've added them in attached v33.

While looking at other callers of index_beginscan(), I was wondering
if systable_beginscan() and systable_beginscan_ordered() should ever
pass SO_HINT_REL_READ_ONLY. I guess we would need to pass if the
operation is read-only above the index_beginscan() -- I'm not sure if
we always know in the caller of systable_beginscan() whether this
operation will modify the catalog. That seems like it could be a
separate project, though, so maybe it is better to say this feature is
just for regular tables.

As for the other cases: We don't have the relation range table index
in check_exclusion_or_unique_constraints(), so I don't think we can do
it there.

And I think that the other index scan cases like in replication code
or get_actual_variable_endpoint() are too small to be worth it, don't
have the needed info, or don't do on-access pruning (bc of the
snapshot type they use).

> Also, comment about visibilitymap_set() says "Callers that log VM changes separately should use visibilitymap_set()" as if visibilitymap_set() is some other function.

Ah, yes, I forgot to remove that when I removed the old
visibilitymap_set() and made visibilitymap_set_vmbits() into
visiblitymap_set(). Done in v33.

- 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