[QGIS-Developer] Processing: No spatial index exists for input layer, performance will be severely degraded

[Nyall Dawson]

On Fri, 27 Nov 2020 at 01:52, Andreas Neumann <a.neumann at carto.net> wrote:
>
> Hi all,
>
> Thanks for your replies/opinions.
>
> @Richard: this message also comes up for intermediate memory layers, not only for Geopackage layers.
>
> @Luigi: if I manually add "create spatial index" often, this very much "pollutes" the model.
>
> I agree with Ujaval, that it would be a better user experience if QGIS would do the indexing automatically (on intermediate layers) for operations where the input doesn't have an index and the algorithm would potentially benefit from an index.

This is a fair enough request -- we could keep the index generation as
a "lazy" thing which is only done when a step in the model indicates
that it's about to benefit from it. I can't see any technical
blockers/disadvantages to this.

>
> Next to automatic indexing I would think that "auto-repairs" for errors that processing algorithms introduce would be good to have, e.g. remove double vertices, remove empty geometries, empty holes/rings, self-intersections. etc.. If this is potentially dangerous, we can do opt-in with central threshold values, and only if the analysis is 2d only. I understand that for 3D analysis automatic cleaning is not always possible.

There's some discussion on this here:
https://github.com/qgis/QGIS/pull/39891#issuecomment-734676128

Nyall

>
> Or maybe a switch to GEOS 3.9 with the "fixed precision model" enabled would remove all these errors previously introduced by processing?
>
> Greetings,
>
> Andreas
>
> On 2020-11-26 16:24, Ujaval Gandhi wrote:
>
> +1 to have an option to generate spatial index automatically for intermediate layers. As I understand, creating index for database layers automatically may not be preferable, but it's reasonable to want this for intermediate memory layers. Since processing can already identify which operations might benefit from the index, it would be much better user experience to take care of it internally.
>
> Ujaval Gandhi
> Spatial Thoughts
> mobile: +91-8095684687
> email: ujaval at spatialthoughts.com
>
>
>
> On Thu, Nov 26, 2020 at 8:26 PM Luigi Pirelli <luipir at gmail.com> wrote:
>
> I've this message constantly... but usually when an intermediate layer is used in some geoprocess. So, you can just add a "create spatial index" step before the next geoprocess. Doing it automatically can be time spending. Do you really need it everytime?
>
> Luigi Pirelli
>
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>
> On Mon, 23 Nov 2020 at 15:23, Andreas Neumann <andreas at qgis.org> wrote:
>
> Hi,
>
> When running QGIS processing models, I frequently get the red warning messages:
>
>
> No spatial index exists for input layer, performance will be severely degraded
>
>
>
> These are temporary (intermediate) geopackage files that QGIS generates during the running of the model. Is there an option that QGIS could automatically generate these spatial indexes for intermediate files?
>
>
>
> Thanks,
>
> Andreas
>
>
> --
> Andreas Neumann
> QGIS.ORG board member (treasurer)
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