[QGIS-Developer] [Qgis-user] Select/extract by location algorithm with same input layers (un)expected results?

[Nyall Dawson]

On Sun, 1 Sep 2019 at 03:05, DelazJ <delazj at gmail.com> wrote:
>
> Hi,
> I don't know whether it's an issue to file or a design so i'm asking beforehand.
>
> If you use select by location algorithm with the same layer as source and comparing, and select a predicate like "within" for example, it returns all the features since it considers a feature to be within itself. Logical but this means that you can not rely on this tool to check whether there are features in the same layer that are within others.
> This applies to most of the other geometric predicates, making them useless in this context.
>
> Question: Should the algorithm not skip same features comparison when we use the same data source? Or are there other tools for features comparison if the layers are the same?

Ha - good question, and not something I've seen discussed before!
Could I request you to do a quick audit of other applications (ArcGIS,
GRASS, etc) and see what behavior they have adopted here?

Nyall


>
> Regards,
> Harrissou
>
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