From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: exclusion@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17792: MERGE uses uninitialized pointer and crashes when target tuple is updated concurrently
Date: Wed, 15 Feb 2023 20:42:24 +0100
Message-ID: <20230215194224.egfyt3j5ewy4c6m3@alvherre.pgsql> (raw)
In-Reply-To: <CAEZATCWTFjn6rCx3=NCQhVaRZyi-w=jj8OEmJx9Fb_em5dh4Ew@mail.gmail.com>
On 2023-Feb-15, Dean Rasheed wrote:
> On Tue, 14 Feb 2023 at 19:19, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > I agree, this looks to be a good fix. However, I couldn't in a quick
> > try reproduce the problem, so I haven't been able to verify it. I'll
> > try to do that early tomorrow.
>
> I did some more testing, and the fix looks good.
Thank you, I have pushed it.
> > (I also delete the XXX comment there.)
>
> That makes sense. It's a bit inconsistent (though not related to this
> bug) that a cross-partition update will return OK if the tuple was
> concurrently deleted, so merge will think that it updated the tuple
> and not try an insert action, whereas for a normal update it will try
> an insert action if the tuple was concurrently deleted. The thing that
> seems wrong there is that ExecUpdateAct() sets updateCxt->updated =
> true for a cross-partition update regardless of whether it actually
> executed the insert half of the update/move. In theory, that flag
> could be set to false so that merge would know if the tuple was
> concurrently deleted, though it's not clear if it's worth it.
Hmm. I wonder if this is just an inconsistency, or rather an outright
bug.
--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
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To: pgsql-bugs@postgresql.org
Cc: alvherre@alvh.no-ip.org, dean.a.rasheed@gmail.com, exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17792: MERGE uses uninitialized pointer and crashes when target tuple is updated concurrently
In-Reply-To: <20230215194224.egfyt3j5ewy4c6m3@alvherre.pgsql>
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