Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries

On 6 November 2012 14:17, Gunnar "Nick" Bluth <gunnar(dot)bluth(at)pro-open(dot)de>wrote:

> Am 06.11.2012 21:08, schrieb Petr Praus:
>
>
>> 2MB: http://explain.depesz.com/s/**ul1 <http://explain.depesz.com/s/ul1>
>> 4MB: http://explain.depesz.com/s/**IlVu<http://explain.depesz.com/s/IlVu>
>> 10MB: http://explain.depesz.com/s/**afx3<http://explain.depesz.com/s/afx3>
>> 12MB: http://explain.depesz.com/s/**i0vQ<http://explain.depesz.com/s/i0vQ>
>>
>> See the change in the plan between 10MB and 12MB, directly at top level?
> That narrows the thing down quite a bit.
>
> Though I wonder why this didn't show in the original plans...

Yes, the 2,4 and 10 are the same, the only difference is number of buckets.
But with 12, it makes completely different choices, it decides to make
sequential scans and hash right joins instead of merge joins. And those
sequential scans take a loong time. Could this be caused by some missing
indices perhaps?

The original plans I posted at the start are the same as the 12MB plan, I'm
not sure why is that, I really hope I didn't make some sort of mistake
there.

Thanks for your help by the way! :-)

>
>
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> Gunnar "Nick" Bluth
> RHCE/SCLA
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> Email: gunnar(dot)bluth(at)pro-open(dot)de
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