Horton

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: 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: 2025-09-03T09:06:40Z
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

On Wed, 3 Sept 2025 at 04:11, Melanie Plageman
<melanieplageman@gmail.com> wrote:
>
> 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



Hi!

small comments regarding new series

0001, 0002, 0017 LGTM


In 0015:

```
reshke@yezzey-cbdb-bench:~/postgres$ git diff
src/backend/access/heap/pruneheap.c
diff --git a/src/backend/access/heap/pruneheap.c
b/src/backend/access/heap/pruneheap.c
index 05b51bd8d25..0794af9ae89 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -1398,7 +1398,7 @@ heap_prune_record_unchanged_lp_normal(Page page,
PruneState *prstate, OffsetNumb
                                /*
                                 * For now always use prstate->cutoffs
for this test, because
                                 * we only update 'all_visible' when
freezing is requested. We
-                                * could use
GlobalVisTestIsRemovableXid instead, if a
+                                * could use GlobalVisXidVisibleToAll
instead, if a
                                 * non-freezing caller wanted to set the VM bit.
                                 */
                                Assert(prstate->cutoffs);
```

Also, maybe GlobalVisXidTestAllVisible is a slightly better name? (The
term 'all-visible' is one that we occasionally utilize)


-- 
Best regards,
Kirill Reshke