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Re: LISTEN/NOTIFY and notification timing guarantees

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: Joachim Wieland <joe(at)mcknight(dot)de>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: LISTEN/NOTIFY and notification timing guarantees
Date: 2010-02-16 21:15:11
Message-ID: 14936.1266354911@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
> On Tue, Feb 16, 2010 at 10:38 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> 2. Add an extra lock to serialize writers to the queue, so that messages
>> are guaranteed to be added to the queue in commit order. As long as

> fwiw, I think you're definitely on the right track.  IMO, any scenario
> where an issued notification ends up being deferred for an indefinite
> period of time without alerting the issuer should be avoided if at all
> possible.  Just to clarify though, does your proposal block all
> notifiers if any uncommitted transaction issued a notify?

It will block other notifiers until the transaction releases its locks,
which should happen pretty promptly --- there are no user-accessible
reasons for it to wait.

			regards, tom lane

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