Simon Riggs <simon at 2ndQuadrant.com> writes:
> On Fri, 2010-12-03 at 12:26 -0500, Christopher Browne wrote:
>> === Commit timestamps ===
>> * per Jan Wieck
>> * Requires PostgreSQL extension
>> * Eliminates need for periodic generation of SYNC events
>> * Simplifies queries for searching for sl_log_* data
>> * Enables carryover of commit times to subscribers
>
> It should be possible to do this using LISTEN/NOTIFY.
> Now we can pass a payload with the NOTIFY, we just need to pass the
> transaction id. That can be handled automatically by trigger.
>
> What we need is commit order, not commit timestamp, yes?
> NOTIFY happens in commit sequence. It doesn't provide the commit
> timestamp, but perhaps that can be provided by the LISTENer, if you
> really need it.

Hmm.  I'm not seeing how that would work out.  Something has to run
NOTIFY at the end of the transaction, and I don't think we have any
component (Slony or Postgres) that does that.

Perhaps it suffices for there to be a commit hook that submits a NOTIFY
with the present txid before completing.  If the timestamp was also
passed back to the LISTENer, that seems like an interesting
approximation to a commit timestamp.

BTW, this is one of the items on the list that we weren't anticipating
would be going in any time soon.  Not everything brainstormed gets done
:-).
-- 
select 'cbbrowne' || '@' || 'afilias.info';
Christopher Browne
"Bother,"  said Pooh,  "Eeyore, ready  two photon  torpedoes  and lock
phasers on the Heffalump, Piglet, meet me in transporter room three"