#
View Source Defining Manual Relationships

Manual relationships allow you to express complex or non-typical relationships between resources in a standard way. Individual data layers may interact with manual relationships in their own way, so see their corresponding guides.

By default, the only thing manual relationships support is being loaded.

##

example

Example

In our Helpdesk example, we'd like to have a way to find tickets

In the `Rep?` resource, define a `has_many` relationship as `manual` and point to the module where it will be implemented.

    relationships do
      has_many :tickets_above_threshold, Helpdesk.Support.Ticket do
        manual Helpdesk.Support.Ticket.Relationships.TicketsAboveThreshold
      end
    end

Using Ash to get the destination records is ideal, so you can authorize access like normal but if you need to use a raw ecto query here, you can. As long as you return the right structure.

The `TicketsAboveThreshold` module is implemented as follows.

    defmodule Helpdesk.Support.Ticket.Relationships.TicketsAboveThreshold do
      use Ash.Resource.ManualRelationship
      require Ash.Query

      def load(records, _opts, %{query: query, actor: actor, authorize?: authorize?}) do
        # Use existing records to limit resultds
        rep_ids = Enum.map(records, & &1.id)

        {:ok,
         query
         |> Ash.Query.filter(representative_id in ^rep_ids)
         |> Ash.Query.filter(priority > representative.priority_threshold)
         |> Helpdesk.Support.read!(actor: actor, authorize?: authorize?)
         # Return the items grouped by the primary key of the source, i.e representative.id => [...tickets above threshold]
         |> Enum.group_by(& &1.representative_id)}
      end
    end

##

using-the-query

Using the Query

Since you likely want to support things like filtering your relationship when being loaded, you will want to make sure that you use the query being provided. However, depending on how you're loading the relationship, you may need to do things like fetch extra records. To do this, you might do things like

    def load(records, _opts, %{query: query, ..}) do
      # unset some fields
      fetch_query = Ash.Query.unset(query, [:limit, :offset])

      # or, to be more safe/explicit, you might make a new query, explicitly setting only a few fields
      fetch_query = query.resource |> Ash.Query.filter(^query.filter) |> Ash.Query.sort(query.sort)

      ...
    end

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