Re: Fuzzy cost comparison to eliminate redundant planning

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От Mike Mascari
Тема Re: Fuzzy cost comparison to eliminate redundant planning
Дата
Msg-id 40674CAD.4000702@mascari.com
обсуждение исходный текст
Ответ на Fuzzy cost comparison to eliminate redundant planning work  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: Fuzzy cost comparison to eliminate redundant planning work  (Tom Lane <tgl@sss.pgh.pa.us>)
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Tom Lane wrote:
> I've been looking at the planner performance problem exhibited by
> Eric Brown:
> http://archives.postgresql.org/pgsql-performance/2004-03/msg00273.php
> 
> While a nine-way join is inherently going to take some time to plan
> (if you don't constrain the search space with JOIN), it seemed to me
> that this particular query was taking even longer than I'd expect.

...
> I found that this reduced the planning time of Eric's> query by about 40%, without changing the resulting plan.

More great news, as always. IIRC you recently bumped the default 
GEQO threshold from eleven to twelve. With your new fuzzy comparison 
patch is twelve still the appropriate number? Or does the fuzzy 
comparison scale all planning time down and therefore the default 
threshold should remain where it is?

Mike Mascari





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