Re: Listen / Notify - what to do when the queue is full

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>

To: Jeff Davis <pgsql@j-davis.com>

Cc: Joachim Wieland <joe@mcknight.de>, Greg Smith <greg@2ndquadrant.com>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, "Florian G. Pflug" <fgp@phlo.org>, Josh Berkus <josh@agliodbs.com>, pgsql-hackers@postgresql.org

Date: 2010-01-20T22:40:26Z

Lists: pgsql-hackers

Jeff Davis <pgsql@j-davis.com> writes:
> On Wed, 2010-01-20 at 15:54 -0500, Tom Lane wrote:
>> Yes.  That is the case with the existing implementation as well, no?
>> We don't consider sending notifies until transaction end, so anything
>> that commits during the xact in which you UNLISTEN will get dropped.

> Only if the transaction containing UNLISTEN commits. Are you saying it
> would also be OK to drop NOTIFYs if a backend's UNLISTEN transaction
> aborts?

No, I would say not, but that wasn't being proposed was it?  The
decisions about what to do are only made at/after commit.

> Thinking out loud: If we're taking this approach, I wonder if it might
> be a good idea to PreventTransactionChain for LISTEN and UNLISTEN?

That shouldn't be necessary IMO.  There's never been such a restriction
before.

			regards, tom lane