| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, Luke Lonergan <LLonergan(at)greenplum(dot)com>, Grzegorz Jaskiewicz <gj(at)pointblue(dot)com(dot)pl>, PGSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Doug Rady <drady(at)greenplum(dot)com>, Sherry Moore <sherry(dot)moore(at)sun(dot)com> |
| Subject: | Re: Bug: Buffer cache is not scan resistant |
| Date: | 2007-03-05 21:03:10 |
| Message-ID: | 22436.1173128590@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> On Mon, 2007-03-05 at 15:30 -0500, Tom Lane wrote:
>> Strikes me that expressing that parameter as a percentage of
>> shared_buffers might make it less in need of manual tuning ...
> The original patch was a percentage of effective_cache_size, because in
> theory it may be helpful to have this parameter larger than shared
> buffers. Synchronized Scannning can take advantage of OS buffer cache as
> well.
I didn't say you couldn't allow it to be more than 100% ;-). But basing
it on effective_cache_size strikes me as a bad idea because that parameter
is seldom better than a wild guess. shared_buffers at least means
something.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Heikki Linnakangas | 2007-03-05 21:03:48 | Re: Bug: Buffer cache is not scan resistant |
| Previous Message | Pavel Stehule | 2007-03-05 20:56:34 | Re: proposal: custom variables management |