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help / color / mirror / Atom feedFrom: Melanie Plageman <[email protected]>
To: Alexander Lakhin <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: David Rowley <[email protected]>
Cc: Kirill Reshke <[email protected]>
Cc: Chao Li <[email protected]>
Cc: Andrey Borodin <[email protected]>
Cc: Xuneng Zhou <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Heikki Linnakangas <[email protected]>
Subject: Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access)
Date: Mon, 20 Apr 2026 12:18:24 -0400
Message-ID: <CAAKRu_aoK6824z_JtJUWMZk2ST2dXN005Gkt05iitTLD2i4OCw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On Sat, Apr 18, 2026 at 2:00 PM Alexander Lakhin <[email protected]> wrote:
>
> 18.04.2026 19:25, Andres Freund wrote:
>
> >> Could you please look if this can be fixed?
> > When you say fix, I assume you mean address the test instability, rather than
> > actual code changes?
>
> Sure, I didn't mean the new behavior is wrong. Probably changing that
> table to temporary would work
Yes, I think changing it to a temp table is the easiest fix. We could
also do autovacuum_enabled=false, I think, but making it a temp table
seems cleanest.
I wonder if we should move the EXPLAIN test above the results queries,
then throw in a vacuum in between some of them so we exercise btree
gist as a bitmap heap scan and as an index only scan. It could provide
a little bit more coverage? Or maybe that isn't actually extra
coverage. I'm not sure.
> but I wonder if there are other queries,
> which plans can change due to the same reason.
I think we'll have to take this on a case-by-case basis when we see
failures. While it is certainly possible other tests just rely on
autovacuum not having run and set the page all-visible, many of them
probably have already had to account for that.
- Melanie
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Subject: Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access)
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