Ash FrameworkAF
Ash Framework•3mo ago•
3 replies
E

Using an inline aggregate of unrelated resource filtering by related resources

I believe I could do this using a custom relationship and falling back to Ecto, but I was wondering if there was a "Ash way" of doing what I'm trying to do here.

I have four resources/tables

SceneWidget

scene_id
widget_version_id


Scene

id
channel_id


WidgetVersion

id
widget_id


WidgetMemory

channel_id (primary)
widget_id (primary)


I'm trying to write a calculation to go from SceneWidget => WidgetMemory

Using SQL I would normally write something like

SELECT widget_memories.*
FROM scene_widgets
JOIN scenes ON scene_widgets.scene_id = scenes.id
JOIN widget_versions ON scene_widgets.widget_version_id = widget_versions.id
JOIN widget_memories ON widget_memories.widget_id = widget_versions.widget_id AND widget_memories.channel_id = scenes.channel_id


Trying to do this as a calculation I've tried:

calculate :memory,
          :map,
          expr(
            first(EKG.Scenes.WidgetMemory,
              query: [
                filter: expr(channel_id == parent(scene.channel_id) and widget_id == parent(widget_version.widget_id))
              ],
              field: :data
            )
          )


and 

calculate :memory,
          :map,
          expr(
            first(EKG.Scenes.WidgetMemory,
              join_filters: %{
                scene: expr(channel_id == parent(channel_id)),
                widget_version: expr(widget_id == parent(widget_id))
              },
              field: :data
            )
          )


But neither seem to work. Does Ash have a suggestion on how to to model these complex relationships? Or are you meant to just fallback to CustomRelationship/Ecto in these situations?
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