| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| 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 16:16:52 |
| Message-ID: | 125.1135095412@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Greg Stark <gsstark(at)mit(dot)edu> writes:
> 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?
Can't see how it would do that.
regards, tom lane
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