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Re: [HACKERS] WAL logging freezing

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] WAL logging freezing
Date: 2006-10-31 01:40:28
Message-ID: 22033.1162258828@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> That was understood; in the above example I agree you need to flush. If
> you don't pass a truncation point, you don't need to flush whether or
> not you actually truncate. So we don't need to flush *every* time,

OK, but does that actually do much of anything for your performance
complaint?  Just after GlobalXmin has passed a truncation point, *every*
vacuum the system does will start performing a flush-n-fsync, which
seems like exactly what you didn't like.  If the syncs were spread out
in time for different rels then maybe this idea would help, but AFAICS
they won't be.

			regards, tom lane

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