From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Stark <gsstark@mit.edu>
Cc: Markus Schaber <schabi@logix-tt.com>
Cc: PostgreSQL Performance List <pgsql-performance@postgresql.org>
Subject: Re: Read only transactions - Commit or Rollback
Date: Tue, 20 Dec 2005 11:16:52 -0500
Message-ID: <125.1135095412@sss.pgh.pa.us> (raw)
In-Reply-To: <87irtjah9m.fsf@stark.xeocode.com>
References: <16F953410A0F1346848DCB476A989CFE01D6AF@swtexchange2.technology.de>
<43A7F303.8040804@logix-tt.com>
<87mziwj6na.fsf@gate450.dyndns.org>
<43A7F9B9.3010906@logix-tt.com>
<29672.1135093688@sss.pgh.pa.us>
<87irtjah9m.fsf@stark.xeocode.com>
Greg Stark <gsstark@mit.edu> writes:
> Tom Lane <tgl@sss.pgh.pa.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?
Can't see how it would do that.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, gsstark@mit.edu, schabi@logix-tt.com
Subject: Re: Read only transactions - Commit or Rollback
In-Reply-To: <125.1135095412@sss.pgh.pa.us>
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