| From: | Melanie Plageman <melanieplageman(at)gmail(dot)com> |
|---|---|
| To: | Alexander Lakhin <exclusion(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Tomas Vondra <tomas(at)vondra(dot)me>, David Rowley <dgrowleyml(at)gmail(dot)com>, Kirill Reshke <reshkekirill(at)gmail(dot)com>, Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Xuneng Zhou <xunengzhou(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Subject: | Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access) |
| Date: | 2026-09-11 17:24:17 |
| Message-ID: | CAAKRu_b=GfvNP4uh-SuWk9zAg0xa7OK=Uc_+mka9WTxBm0yoAg@mail.gmail.com |
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On Thu, Sep 10, 2026 at 3:25 PM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
>
> It also reported that since d96f87332b3 the FSM will be less up to
> date on the standby since COPY FREEZE criteria for updating the FSM is
> if (action == BLK_NEEDS_REDO && freespace < BLCKSZ / 5) and the old
> VM record replay code had no such freespace check. I'll post a patch
> to fix that tomorrow. The fix is pretty simple: just update the FSM if
> the heap multi insert record sets the VM.
Here is a patch for this. While writing it, I realized I do not
understand why we don't update the FSM when restoring an FPI --
especially for COPY FREEZE. The FSM won't be up-to-date after
promotion for those pages and vacuum won't scan them so they'll remain
that way forever. Obviously not something to change in backbranches,
but it strikes me as odd that we do that in any cases -- but
especially for COPY FREEZE.
- Melanie
| Attachment | Content-Type | Size |
|---|---|---|
| v1-0001-Update-FSM-in-COPY-FREEZE-replay.patch | text/x-patch | 3.3 KB |
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