Feedback-ID: ia2694551:Fastmail
Date: Thu, 24 Aug 2023 09:50:44 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>,
	Thomas Munro <thomas.munro@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: subscription/015_stream sometimes breaks
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On 2023-Aug-24, Amit Kapila wrote:

> On Wed, Aug 23, 2023 at 1:31 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> > Hmm, I think if worker->in_use is false, we shouldn't consult the rest
> > of the struct at all, so I propose to add the attached 0001 as a minimal
> > fix.
> 
> I think that way we may need to add the check for in_use before
> accessing each of the LogicalRepWorker struct fields or form some rule
> about which fields (or places) are okay to access without checking
> in_use field.

As far as I realize, we have that rule already.  It's only a few
relatively new places that have broken it.  I understand that the in_use
concept comes from the one of the same name in ReplicationSlot, except
that it is not at all documented in worker_internal.h.

So I propose we do both: apply Zhijie's patch and my 0001 now; and
somebody gets to document the locking design for LogicalRepWorker.

> > In fact, I'd go further and propose that if we do take that stance, then
> > we don't need clear out the contents of this struct at all, so let's
> > not.  That's 0002.
> 
> Personally, I think we should consider this change (0002 and 0002) separately.

I agree.  I'd maybe even retract them.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/