Re: Query with no result set, really really slow adding ORBDER BY / LIMIT clause

2017-04-21 9:05 GMT+02:00 Marco Renzi <renzi(dot)mrc(at)gmail(dot)com>:

>
>
>> I am thinking so limit 10000 should be ok. Too big number can be messy
>> for optimizer similarly like too small number.
>>
>> The planner is driven by statistics - and the statistics are not perfect
>> - usually it is working on 80% - like weather forecasting.
>>
>> Usually it is working, but sometimes not.
>>
>> Regards
>>
>> Pavel
>>
>>
>>
> Thanks Pavel, i almost found two solutions at the end:
> One is to use an inner limit as you said, and the other, when you just
> know what the filter is,
> is to try to join with SELECTS that have to be executed first from the
> planner.
>
> Eg
> SELECT fase.id
> FROM tipofase
> JOIN fase
> ON (fase.tipofase = (SELECT tipofase.id FROM tipofase WHERE
> tipofase.agendafrontoffice = true))
>
> ORDER BY fase.id DESC limit 10 offset 0
>
> Thanks for the help
>

yes, sometimes when the data are not homogeneous more queries are necessary

Regards

Pavel

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