Re: [PATCH] vacuum: stop using stream ring after failsafe

From: Melanie Plageman <melanieplageman(at)gmail(dot)com>
To: Jingtang Zhang <mrdrivingduck(at)gmail(dot)com>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Subject: Re: [PATCH] vacuum: stop using stream ring after failsafe
Date: 2026-08-06 21:50:16
Message-ID: CAAKRu_Zse14nSNeCgtnE1LUAH8Of7OmYR+Cc3O_DAzxt3m6T-g@mail.gmail.com
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On Thu, Aug 6, 2026 at 4:42 PM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
>
> Instead, I propose we just take a small hit to the accounting and
> simply clear the ReadBuffersOperations->strategy even of in-progress
> IOs. It should only misattribute a bit of wait time -- and only for a
> limited number of IOs once -- when we enter failsafe mode. It makes
> for a simple, backpatchable solution. I've attached here what I intend
> to commit later today.

Okay, I pushed it, but right after pushing it I suddenly had the
thought, omg, it loops through all the ReadBuffersOperations and sets
them to NULL for _every_ page after entering failsafe mode. And we
obviously ought to fix that. Proposed patch to do that with a simple
local variable is attached. This time I'll let this one sit for longer
before pushing to avoid mistakes like last time.

- Melanie

Attachment Content-Type Size
0001-Only-clear-VACUUM-s-read-stream-strategy-once-in-fai.patch text/x-patch 1.9 KB

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