Horton

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: Andrey Borodin <x4mmm@yandex-team.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2025-09-02T23:11:01Z
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 Tue, Sep 2, 2025 at 5:52 PM Melanie Plageman
<melanieplageman@gmail.com> wrote:
>
> On Thu, Aug 28, 2025 at 5:12 AM Kirill Reshke <reshkekirill@gmail.com> wrote:
> >
> > I did micro git-blame research here. I spotted only one related change
> > [0]. Looks like before this change pin was indeed needed.
> > But not after this change, so this visibilitymap_pin is just an oversight?
> > Related thread is [1]. I quickly checked the discussion in this
> > thread, and it looks like no one was bothered about these lines or VM
> > logging changes (in this exact pin buffer aspect). The discussion was
> > of other aspects of this commit.
>
> Wow, thanks so much for doing that research. Looking at it myself, it
> does indeed seem like just an oversight. It isn't harmful since it
> won't take another pin, but it is confusing, so I think we should at
> least remove it in master. I'm not as sure about back branches.

I've updated the commit message in the patch set to reflect the
research you did in attached v8.

- Melanie