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Re: [Bizgres-general] WAL bypass for INSERT, UPDATE and

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Hannu Krosing <hannu(at)skype(dot)net>
Cc: Greg Stark <gsstark(at)mit(dot)edu>, Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [Bizgres-general] WAL bypass for INSERT, UPDATE and
Date: 2005-12-28 00:30:12
Message-ID: 9450.1135729812@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Hannu Krosing <hannu(at)skype(dot)net> writes:
> making one of WAL files (strategies) be /dev/null would almost get us
> non-logged writes, except for a little overhead in write() calls.
> fsync() on /dev/null should be instantaneous .

No, you really do want to push it up to a higher level than that.
The CPU and contention costs of generating a WAL record are nontrivial,
and doing so only to throw it away is pretty silly.  What's more,
pointing WAL at /dev/null would disable logging for the entire database
cluster, not just selected tables which is what people seem to be
asking for in this thread.  (No, I don't wish to deal with multiple
WAL output streams...)

			regards, tom lane

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