Re: Idle idea for improving concurrency of LISTEN/NOTIFY

Added to TODO:

o Improve LISTEN concurrency

http://archives.postgresql.org/pgsql-hackers/2008-02/msg01106.php

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Tom Lane wrote:
> Sooner or later we ought to completely reimplement LISTEN/NOTIFY,
> but while thinking about Joel Stevenson's performance issue I had a
> sudden idea for a very simple change that would buy some improvement.
> Currently, all operations in async.c take ExclusiveLock on pg_listener,
> but it strikes me that that is overkill. Wouldn't it work fine to
> take a plain writer's lock (ie, RowExclusiveLock) for operations that
> are touching only the current backend's pg_listener entries? We would
> only need ExclusiveLock when we want to scribble on *other* backends'
> entries, ie, only in AtCommit_Notify(). What this would mean is that
> when a NOTIFY awakens multiple listeners, the listeners don't serialize
> on the pg_listener lock in order to find and clear their table entries.
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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