Re: NOTIFY/LISTEN on read-only slave?

Tom Lane wrote:
> Greg Smith <greg(at)2ndquadrant(dot)com> writes:
> > What's the actual reason for the restriction then?
>
> Well, NOTIFY doesn't seem very sensible for a read-only slave to
> execute: it can't change the database state so there's nothing for
> it to notify about. Ideally we should allow slave sessions to LISTEN
> to notify events that were generated on the master, though. The recent
> patch eliminates the major impediments to doing that, but we're still
> shy of some infrastructure to do it --- mainly, some code to push
> notify events through the WAL stream. (Presumably this would have to be
> something you could enable or disable, because WAL-logging notifies
> on a machine that wasn't an HS master would be a large and very useless
> performance overhead.)

I assumed people would want to do listen/notify on the slave only, or is
there no good use for that? I don't see passing notify information from
the master to the slave as useful.

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

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