From: Álvaro Herrera <alvherre@kurilemu.de>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>
Cc: Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>
Cc: exclusion@gmail.com <exclusion@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #18988: DROP SUBSCRIPTION locks not-yet-accessed database
Date: Mon, 4 Aug 2025 14:50:34 +0200
Message-ID: <202508041250.6qjjfgnqe7mi@alvherre.pgsql> (raw)
In-Reply-To: <CAFiTN-vhc4rEqfXMYkPvaoRbr8_ZFpcBDNV3mUVaOfZfMAdHdQ@mail.gmail.com>
On 2025-Aug-04, Dilip Kumar wrote:
> I have worked on this and produced a first version of patch, let's see
> what others think about this idea. It would have been better if we
> could use SysCache for rechecking the subscription, but since we are
> not connected to the database in the launcher we can not use the
> SysCache, at least that's what I think.
I think it's reasonable to recheck after locking. There's a comment in
DropSubscription that says we get AEL, which is no longer true. In
is_subscription_exists() you should use the index on OID instead of
seqscanning the catalog without a scankey; also I think the name ought
to be "does" rather than "is". I think it's really odd that that
function opens and closes a transaction; sounds to me that something
like that really belongs in the caller (frankly the same is true with
the other function that your comment references). Why isn't
systable_beginscan being used to scan the catalog?
I think with this coding, the resource owner for this new lock is NULL.
Is this really a good approach? Maybe there should be a resowner here.
--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"Always assume the user will do much worse than the stupidest thing
you can imagine." (Julien PUYDT)
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To: pgsql-bugs@postgresql.org
Cc: alvherre@kurilemu.de, dilipbalaut@gmail.com, vignesh21@gmail.com, kuroda.hayato@fujitsu.com, exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18988: DROP SUBSCRIPTION locks not-yet-accessed database
In-Reply-To: <202508041250.6qjjfgnqe7mi@alvherre.pgsql>
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