Ecto Nested Preload Filter Referencing Top Level Assoc Join

Questions / Help
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1

I have a nested preload with a has_many relation and I would love to filter these references by a join I did on the top level, Here is my naive thinking:

 query =
      from vm in VariantMarket,as: :vm,
        left_join: m in assoc(vm, :market), as: :m,
        where: vm.id in ^ids,
        preload: [
          variant: [product: [market_settings: ^pms_query.()]]
        ]

and for pms_query I was hoping I could us the dynamic helper like this:

 pms_query = fn ->
     market_filter = dynamic([pm: pm, m: m], m.id == pm.market_id)
     from pm in Pdex.Catalog.ProductMarket,
        as: :pm,
        where: ^market_filter
    end

But I get ann error saying

unknown bind name `:m` in query

As far as I understand this, it’s not possible to reference any top-level joins within a preload. I also tried subqueries with parent_as in the preload part but that was also unsuccessful.

I know I could solve this particular case with a few more joins on the product assoc and then the market_setting assoc, which I could then reference directly in the preload.

But this is just an example to test this kind of filtering. I have a more complex example where multiple joins would be a nightmare.

I get the impression it’s, in general, not possible to simply use a top-level reference as a filter in a preload. Maybe because of the order of interpolation.

But maybe I am just not understanding the dynamic helper at all, and someone could give me a hand, or could at least confirm my assumption.

Thanks in advance

Bjorn