| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Greg Stark <stark(at)mit(dot)edu>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>, Ants Aasma <ants(at)cybertec(dot)at>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Markus Wanner <markus(at)bluegap(dot)ch> |
| Subject: | Re: Proposal for CSN based snapshots |
| Date: | 2014-08-27 05:23:08 |
| Message-ID: | 1409116988.2335.463.camel@jeff-desktop |
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| Lists: | pgsql-hackers |
On Tue, 2014-08-26 at 13:45 +0300, Heikki Linnakangas wrote:
> Yeah. This patch in the current state is likely much much slower than
> unpatched master, except in extreme cases where you have thousands of
> connections and short transactions so that without the patch, you spend
> most of the time acquiring snapshots.
What else are you looking to accomplish with this patch during this
'fest? Bug finding? Design review? Performance testing?
I haven't had a good track record with my performance testing recently,
so I'm unlikely to be much help there.
It seems a bit early for bug hunting, unless you think it will raise
possible design issues.
I think there's already at least one design issue to consider, which is
whether we care about CLOG/CSNLOG access for hinted records where the
xid > snapshot->xmin (that is, accesses that previously would have
looked at xip). Would more discussion help here or do we need to wait
for performance numbers?
Regards,
Jeff Davis
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