Freeze when using aggregate in a virtual field

[3nids]

Using a layer with 1 feature, the following expression: aggregate('test','sum',"HECTARES","TYPE"=attribute(@parent,'TYPE'))

using this as a label causes no issue
using it in virtual field leads to a freeze (see the stack trace)

it doesn't seem to be related to the backend (tested with PG and GPKG)

example project and data:
issue-aggregate-virtual.zip
see the expression used in labelling, try to use it as a virtual field

So far, it looks like an infinite recursion in the aggregate as it uses the parent feature.

Stack trace:

[3nids]

The solution is to use a with_variable:

with_variable('type_value', "TYPE", aggregate('test','sum',"HECTARES","TYPE"=@type_value))

[roya0045]

What is the point of "TYPE"=attribute(@parent,'TYPE') anyway? IRL I don't see why anyone would compare a field value to itself.

[3nids]

This can be used for instance to calculate aggreagates on a rolling window (cumulative sum up to the feature for instance).

[roya0045]

Ah you mean when you need to fix a variable to the feature of origin and let the other one be dynamic? This would make sense. This seems unintuitive with 'with_variable', and using 'attribute' is only a way to fetch the field in a dynamic way (at leas this is how I use it in my models).

I assume this is caused by the fact that you fix the variable outside of the scope are than check it when evaluating...

[garci66]

I know the issue is wont_fix, but I am having a very similar issue without even using the @parent. Just using aggregate in the virtual field (my operation is count) is enough to hang the UI.

[garci66]

In my case, the "with_variable" still didnt solve it. In fact, also other functions, such as "count" in a virtual field caused qgis to crash each time I applied the changes.

[roya0045]

We would need the data and expression/project if someone wants to investigate.

[garci66]

The following is the project file:
Herramienta de diseño.zip

then in the layer called NAPs I create a new virtual field (of type integer) and use the following formula:

with_variable('p_id_Acceso',"id_Acceso",
with_variable('p_s_distance',"s_distance" ,
	count('id',filter:="id_Acceso"=@p_id_Acceso and "s_distance"<@p_s_distance)))+1	

and as soon as I apply the changes it fails. If I create a calculated (non-virtual) field, it works fine.

I know here i am not using the aggregate function, but I was using the "count" workaround as an option to the following:

aggregate('NAPs','count','id',"id_Acceso"=attribute(@parent,'id_Acceso') and "s_distance"<attribute(@parent,'s_distance'))+1

(both the id_Acceso and s_distance are also virtual fields. Might be related to that?

[Pedro-Murteira]

This issue is still valid on QGIS 3.22.3. (Windows 10)