From: PFC <lists@peufeu.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: Christian Storm <christian.storm@gmail.com>
Cc: Jim C. Nasby <jnasby@pervasive.com>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: pgmemcache
Date: Thu, 13 Apr 2006 22:23:31 +0200
Message-ID: <op.s7yqxh1ycigqcu@apollo13> (raw)
In-Reply-To: <26792.1144949880@sss.pgh.pa.us>
References: <1144135482.063425.33380@z34g2000cwc.googlegroups.com>
<20060411225515.GZ49405@pervasive.com>
<op.s7vvyggtcigqcu@apollo13>
<200604121603.43986.josh@agliodbs.com>
<20060413001024.GP49405@pervasive.com>
<6236.1144888514@sss.pgh.pa.us>
<4D23826E-7325-4946-B79A-80E321E0E497@gmail.com>
<26792.1144949880@sss.pgh.pa.us>
> An AFTER COMMIT trigger would have to be in a separate transaction.
I guess AFTER COMMIT triggers would be like a NOTIFY, but more powerful.
While NOTIFY can't transmit information to another process, this trigger
could, and the other process could then view the results of the commited
transaction.
Also, implementing a long process (something involving network
roundtrips, for instance) in a BEFORE COMMIT trigger would delay the
transaction and any locks it holds with no benefit.
> What happens if there's more than one, and one of them fails?
Each one in its own transaction ?
> Even more to the point, if it's a separate transaction, don't you have
> to fire all these triggers again when you commit that transaction?
> The idea seems circular.
I guess AFTER COMMIT triggers are most useful when coupled to a trigger
on a modification to a table. So, the "before / after commit" could be an
attribute of an AFTER INSERT/UPDATE/DELETE trigger. If the AFTER COMMIT
trigger doesn't do any modifications to the target table, there will be no
infinite loop.
The before/after commit could also be implemented not via triggers, but
via deferred actions, by telling postgres to execute a specific query just
before/after the transaction commits. This could be used to implement the
triggers, but would also be more generic : a trigger on INSERT could then
defer a call to memcache update once the transaction is commited. It gets
lisp-ish, but it would be really cool?
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: lists@peufeu.com, tgl@sss.pgh.pa.us, christian.storm@gmail.com, jnasby@pervasive.com, josh@agliodbs.com
Subject: Re: pgmemcache
In-Reply-To: <op.s7yqxh1ycigqcu@apollo13>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox