[QGIS-Developer] Virtual Layer & Unique identifier column?

[Richard Duivenvoorde]

We (Raymond and me) have some issues with Virtual Layer functionality.

Who knows what the actual use is of the 'Unique identifier column' of the dialog? Because without it it also works...

Main point: if you click/use the 'Unique identifier column', and use a NON unique column(!), you are practically filtering your data.... but it's not clear WHAT is used or filtered ... and as an example: the feature count then still shows 5 but the attribute table only shows 3 (filtered)

What do other providers do in such case (I think postgis tells you: "hey that column is NOT unique"?).

We found other ui-related things, which we were not sure if it is interesting enough to create issues for:
- clicking Help button does NOT bring you to: https://docs.qgis.org/testing/en/docs/user_manual/managing_data_source/create_layers.html#creating-virtual-layers
- you can click the 'Unique' checkbox without giving the actual column (could be checked for?)
- test button does not check for missing unique column name
- removing the checkbox (and overwriting the layer) does not remove it (unless you also remove the column name)
- if you 'edit' a v-layer (via context menu) you are still being asked to overwrite/create the layer
- creating a new geometry without a crs seems possible (could be checked for?)
etc

Would this be a good candidate for some nice re-work? We do have some idea's and (other) issues :-)
Our feeling is that current status could need some QGIS-love...

Regards,

Richard Duivenvoorde