| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Greg Sabino Mullane <greg(at)turnstep(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Re: [COMMITTERS] pgsql: Rewrite GEQO`s gimme_tree function so that it always finds a |
| Date: | 2009-12-01 19:07:22 |
| Message-ID: | 5327.1259694442@sss.pgh.pa.us |
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| Lists: | pgsql-committers pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Tue, Dec 1, 2009 at 11:39 AM, Greg Sabino Mullane <greg(at)turnstep(dot)com> wrote:
>> What about 14? Could we at least raise it to 14? 1/2 :)
> I doubt we can raise it at all without lying to ourselves about the
> likely results of so doing. The GEQO planning times are in the low
> double digits of milliseconds. My apps typically have a budget of at
> most ~200 ms to plan and execute the query, and I'm not always
> operating on empty tables.
The reason this is a configurable parameter is so that people can tune
it to their own needs. I think the current default fits all right with
our usual policy of being conservative about hardware requirements.
regards, tom lane
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