| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Joachim Wieland <joe(at)mcknight(dot)de> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Florian G(dot) Pflug" <fgp(at)phlo(dot)org>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Listen / Notify - what to do when the queue is full |
| Date: | 2009-11-20 09:48:44 |
| Message-ID: | 4B0665FC.8000308@enterprisedb.com |
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| Lists: | pgsql-hackers |
Joachim Wieland wrote:
> On Fri, Nov 20, 2009 at 7:51 AM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>>> Note that we don't preserve notifications when the database restarts.
>>> But 2PC can cope with restarts. How would that fit together?
>> The notifications are written to the state file at prepare. They can be
>> recovered from there and written to the queue again at server start (see
>> twophase_rmgr.c).
>
> Okay, but which of the backends would then leave its pointer at that
> place in the queue upon restart?
>
> This is also an issue for the non-restart case, what if you prepare
> the transaction in one backend and commit in the other?
The dummy procs that represent prepared transactions need to be treated
as backends. Each prepared transaction needs a slot of its own in the
backends array.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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