Re: Slow query: bitmap scan troubles

On Tue, Dec 4, 2012 at 2:22 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> On Tue, Dec 4, 2012 at 7:27 AM, Claudio Freire <klaussfreire(at)gmail(dot)com> wrote:
>> On Tue, Dec 4, 2012 at 12:06 PM, <postgresql(at)foo(dot)me(dot)uk> wrote:
>>> Slow version with bitmapscan enabled: http://explain.depesz.com/s/6I7
>>> Fast version with bitmapscan disabled: http://explain.depesz.com/s/4MWG
>>
>> If you check the "fast" plan, it has a higher cost compared against
>> the "slow" plan.
>>
>> The difference between cost estimation and actual cost of your
>> queries, under relatively precise row estimates, seems to suggest your
>> e_c_s or r_p_c aren't a reflection of your hardware's performance.
>
> But the row estimates are not precise at the top of the join/filter.
> It thinks there will 2120 rows, but there are only 11.

Ah... I didn't spot that one...