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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Joel Jacobson <joel@compiler.org>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue
Date: Tue, 04 Nov 2025 09:44:28 -0500
Message-ID: <515740.1762267468@sss.pgh.pa.us> (raw)
In-Reply-To: <66213fee-00ff-4952-802d-c06454e521ac@iki.fi>
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Heikki Linnakangas <hlinnaka@iki.fi> writes:
> Fortunately that's easy to fix: We can move the IsListeningOn() check 
> after releasing the lock. See attached.
> The elephant in the room of course is that a lookup in a linked list is 
> O(n) and it would be very straightforward to replace it with e.g. a hash 
> table. We should do that irrespective of this bug fix. But I'm inclined 
> to do it as a separate followup patch.

There is a different patch series that's concerned with improving
NOTIFY throughput [1].  I think this one should just focus on
fixing the XID problem.

			regards, tom lane

[1] https://commitfest.postgresql.org/patch/6078/





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  To: pgsql-hackers@postgresql.org
  Cc: tgl@sss.pgh.pa.us, hlinnaka@iki.fi, joel@compiler.org
  Subject: Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue
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