I am creating a tree survey system in QGIS. There will be three geometry layers (called 'Single Trees', 'Line of Trees & Hedges', 'Groups of Trees') and each of those layers has a 'TreeUUID' field that generates a UUID automatically.

I want to be able to link features on these layers to another layer ('stems') so that a feature one of the first 3 layers can potentially have multiple entries into 'stems'.

My attempt was to create a polymorphic relationship like this: Polymorphic attempt 1

However I cannot then create the relation reference field on the 'stems' layer: stems form

It looks to me like it should work. I can create a child feature on 'stems' from the main 3 layers but they do not link properly once created. I am unsure exactly what I am missing and there seems to be relatively little information available about polymorphic relationships in QGIS. Does anyone have any ideas?

  • 1
    This could help : opengis.ch/2022/11/29/…
    – J.R
    Commented Dec 1, 2022 at 16:12
  • I had looked through that but there isn't really anything specific to polymorphic relationships. I am wondering if I just have to use a series of 1-n relations from my main layers to the 'stems' layer.
    – Nathan
    Commented Dec 1, 2022 at 16:21
  • They use a polymorphic relation with the "Document Management System Widgets" as I have not used it I can't say if it will work with "non document feature"...
    – J.R
    Commented Dec 1, 2022 at 16:43
  • Facing the same behavior in QGIS 3.34.3. Commented Feb 22 at 11:20


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