[gdal-dev] Faster alternative to GetFeatureCount?

[Roman Breitfuss-Schiffer]

Hi Jon!

I don't know if there's an alternative to GetFeatureCount. At least I 
couldn't find one in the API documentation. Maybe there's a workaround 
I'm not aware of...

What you could do is wrap the call of GetFeatrueCount in a function 
which is killed after some time (2 approaches are discussed here: 
https://stackoverflow.com/questions/40915527/kill-function-after-a-given-amount-of-time). 
With that approach the question remains of getting the value of 
GetFeatureCount when the function gets killed. One could assume that 
there are more features than 1 if the function takes too long. This 
assumption might be a bit risky though...

Best regards
Roman

Am 20.01.2022 um 10:00 schrieb Jon Morris:
>
> I'm writing applications using the GDAL Python bindings and when I 
> profile for performance, GetFeatureCount frequently comes out near the 
> top. I'm often using it to check whether a spatial or attribute filter 
> has returned any features and don't need the full count. When the 
> layer contains millions of features, there would be a big performance 
> improvement if we could exit the count early.
>
> Is there a better way of doing this? I've tried using GetNextFeature 
> instead, but there must be quite a lot of overhead in that function as 
> it is much slower. All I need to know is if the layer has has 0, 1 or 
> >1 features, I don't need the actual count. Can anyone suggest the 
> fastest way of doing this in Python? I'm using GDAL 3.3.1 at the 
> moment but could upgrade if there is new functionality that would help.
>
> Thanks,
>
> Jon
>
> *Jon Morris*
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