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

Peter Eisentraut <peter@eisentraut.org>

From: Peter Eisentraut <peter@eisentraut.org>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: 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>, Kirill Reshke <reshkekirill@gmail.com>
Date: 2025-12-13T13:59:29Z
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 20.11.25 18:19, Melanie Plageman wrote:
> +	prstate->deadoffsets = (OffsetNumber *) presult->deadoffsets;

In your patch 
v22-0001-Split-heap_page_prune_and_freeze-into-helpers.patch, the 
assignment above casts away the const qualification of the function 
argument presult:

+static void
+prune_freeze_setup(PruneFreezeParams *params,
+				   TransactionId new_relfrozen_xid,
+				   MultiXactId new_relmin_mxid,
+				   const PruneFreezeResult *presult,
+				   PruneState *prstate)

(The cast is otherwise unnecessary, since the underlying type is the 
same on both sides.)

Since prstate->deadoffsets is in fact later modified, this makes the 
original const qualification invalid.

I suggest the attached patch to remove the faulty const qualification 
and the then-unnecessary cast.