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Re: Read only transactions - Commit or Rollback

From: Greg Stark <gsstark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Markus Schaber <schabi(at)logix-tt(dot)com>, PostgreSQL Performance List <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Read only transactions - Commit or Rollback
Date: 2005-12-20 16:02:29
Message-ID: 87irtjah9m.fsf@stark.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-performance
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> That surprises me too --- can you provide details on the test case so
> other people can reproduce it?  AFAIR the only performance difference
> between SERIALIZABLE and READ COMMITTED is the frequency with which
> transaction status snapshots are taken; your report suggests you were
> spending 30% of the time in GetSnapshotData, which is a lot higher than
> I've ever seen in a profile.

Perhaps it reduced the amount of i/o concurrent vacuums were doing?

-- 
greg


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