| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Subject: | Re: Review remove {join, from}_collapse_limit, add enable_join_ordering |
| Date: | 2009-07-16 17:26:22 |
| Message-ID: | 12841.1247765182@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Jul 16, 2009 at 11:32 AM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> So maybe a redesign of the equivalence-class joinclause mechanism is in
>> order. Still, this is unlikely to fix the fundamental issue that the
>> time for large join problems grows nonlinearly.
> Nonlinear is one thing, but this looks more like exponential. I
> understand that the standard planner is exponential; GEQO should not
> be.
Well, the equivclass code is new as of 8.3. It's possible that this
got broken relatively recently ...
regards, tom lane
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