@current_parent_value function not working in parent-child table relationships

[tomasMizera]

Description

The @current_parent_value function does not work correctly when used in a child table form to retrieve a value from a parent table in a parent-child relationship between two tables.

Steps to Reproduce

1. Set up a project with two tables linked via a parent-child (1:N) relationship
2. In the child table form, use @current_parent_value('field_name') to reference a field from the parent table
3. Open the child form from the parent feature

Expected Behavior

The @current_parent_value expression should resolve and return the correct value from the parent feature.

Actual Behavior

The function does not return the expected value from the parent table.

Workaround

Using the aggregate() function can serve as a workaround, but native support for @current_parent_value would be the preferred solution.

Environment

• App: Mergin Maps Mobile

[robinbonnefoy]

Hi,

I'm also experiencing this issue and it is very blocking for my work and my teams in the field.

Our use case: we have a parent layer (traps) and a child layer (surveys). When adding a new survey from a trap, we need to auto-increment a survey number based on the count of existing child features for that parent (and others fileds). This works perfectly in QGIS desktop but fails completely in Mergin Maps because @current_parent_value is not supported.

We have tried every workaround we could find — aggregate() with filter, relation_aggregate(), with_variable() — but all of them ultimately require being able to reference the parent feature's key from the child form, which is exactly what @current_parent_value should provide.

Is there any workaround or timeline for a fix? This would be a critical improvement for many users working with relational data in Mergin Maps.

Thank you.

[tomasMizera]

Hi @robinbonnefoy, the fix is scheduled for the next release (in May). Sorry for the trouble!