| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, marcin mank <marcin(dot)mank(at)gmail(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: per table random-page-cost? |
| Date: | 2009-10-20 02:21:24 |
| Message-ID: | f67928030910191921r5a9a3d7en58847920d1a89bd8@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Oct 19, 2009 at 4:29 PM, Greg Stark <gsstark(at)mit(dot)edu> wrote:
> On Mon, Oct 19, 2009 at 4:21 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> marcin mank <marcin(dot)mank(at)gmail(dot)com> writes:
>>>> This proposal is just "hints by the back door", ISTM. As Tom says, there is
>>>> a justification for having it on tablespaces but not on individual tables.
>>
>>> If the parameter is defined as "the chance that a page is in cache"
>>> there is very real physical meaning to it.
>>
>> We have no such parameter...
>
>
> And we want our parameters to be things the DBA has a chance of being
> able to estimate.
Do the current parameters meet that standard? When setting
seq_page_cost now, don't people have a lot of "Well, we're about this
likely to find it in the cache anyway" built into their settings?
Jeff
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