[gdal-dev] Faster alternative to GetFeatureCount?

[Jon Morris]

Hi Ian,

That's more or less what I was doing, calling GetNextFeature twice. I figured GetFeatureCount would be doing that under the hood anyway, but it didn't seem to run any faster.

Jon


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From: Ian Turton <ijturton at gmail.com>
Sent: 20 January 2022 10:55
To: Jon Morris <Jon.Morris at jbarisk.com>
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Faster alternative to GetFeatureCount?

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I'm not sure if it's a shortcut but couldn't you do a getFeatures loop with a counter and break after 2 times round the loop, then your counter would be 0,1 or 2 for your 3 cases.

Ian



On Thu, 20 Jan 2022 at 09:00, Jon Morris <Jon.Morris at jbarisk.com<mailto:Jon.Morris at jbarisk.com>> wrote:
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
Software Developer


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