[QGIS-Developer] point in polygon strikes again: big performance issue

[Jorge Gustavo Rocha]

Hi David,

Yes, yes. I've tried the same! We can say that a spatial join can beat
an attribute based join in performance!

Regards,

Jorge

Às 23:51 de 14/03/21, David Strip escreveu:
> On 3/14/2021 5:34 PM, Jorge Gustavo Rocha wrote:
>> Hi David,
>>
>> Thanks for replication this issue. "Join attributes by location
>> (summary)" is definitely the best choice for this use case. It creates
>> the new layer in a few seconds. That's why I think we are missing
>> something (spatial indexes?, dependency graph?) in the expression engine.
>>
>> There are anomalies in the data. That's almost the same with any dataset
>> we start working with :-)
>>
>> Regards,
>>
>> Jorge
> I tried a different approach, using aggregate, matching on the country
> name, thinking that would be faster than a spatial check.
> I created a new field with the expression:
> 
>     aggregate( '03-03-2021','sum', "Confirmed", "Country_Region" ILIKE attribute(@parent,'SOVEREIGNT'))
> 
> Much to my surprise, this was slower than "Join attributes by location
> (summary)"
> 

J. Gustavo
-- 
Jorge Gustavo Rocha
Departamento de Informática
Universidade do Minho
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