| From: | Greg Stark <gsstark(at)mit(dot)edu> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | 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: | 2009-10-19 23:29:05 |
| Message-ID: | 407d949e0910191629w7607e384g24535e3d760a811c@mail.gmail.com |
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| Lists: | pgsql-hackers |
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. How would you come up with sensible figures for this
hypothetical parameter?
--
greg
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