Ash Elixir•3y ago

Calculate aggregations?

I want to sum_1 = sum_some_data(user_1, :column_1), sum_2 = sum_some_data(user_1, :column_2) then sum_1 - sum_2 and return this value.

9 Replies

ZachDaniel•3y ago

Can you provide a concrete example of the kind of data this might be? like for each user, its the sum of some related value?

dj_gokuOP•3y ago

defmodule Mod.OneOnOne do
  use Ash.Resource,
    data_layer: AshPostgres.DataLayer

  postgres do
    table("one_on_one")
    repo(Mod.Repo)
  end

  actions do
    defaults([:create, :read, :update, :destroy])

    update :assign do
      accept([])

      argument :user_1_id, :uuid do
        allow_nil?(false)
      end

      argument :user_2_id, :uuid do
        allow_nil?(false)
      end

      # change(manage_relationship(:user_1_id, :user, type: :append_and_remove))
      # change(manage_relationship(:user_2_id, :user, type: :append_and_remove))
    end
  end

  attributes do
    uuid_primary_key(:id)
  end

  relationships do
    belongs_to :user_1_id, User
    belongs_to :user_2_id, User
  end
end

defmodule Mod.OneOnOne do
  use Ash.Resource,
    data_layer: AshPostgres.DataLayer

  postgres do
    table("one_on_one")
    repo(Mod.Repo)
  end

  actions do
    defaults([:create, :read, :update, :destroy])

    update :assign do
      accept([])

      argument :user_1_id, :uuid do
        allow_nil?(false)
      end

      argument :user_2_id, :uuid do
        allow_nil?(false)
      end

      # change(manage_relationship(:user_1_id, :user, type: :append_and_remove))
      # change(manage_relationship(:user_2_id, :user, type: :append_and_remove))
    end
  end

  attributes do
    uuid_primary_key(:id)
  end

  relationships do
    belongs_to :user_1_id, User
    belongs_to :user_2_id, User
  end
end

sum_one_on_one(user_1, :user_1_id) - sum_one_on_one(user_1, :user_2_id)

ZachDaniel•3y ago

So sum_one_on_onein this case, would do something like be the count of users that a person is connected to?

dj_gokuOP•3y ago

It is summing how many one_on_one where they were :user_1_id and subtracting that from the sum of one_on_one where they were :user_2_id

ZachDaniel•3y ago

relationships do
  has_many :user_1_one_on_ones, Mod.OneOnOne do
    destination_attribute :user_1_id
  end

  has_many :user_2_one_on_ones, Mod.OneOnOne do
    destination_attribute :user_2_id
  end
end

aggregates do
  count :count_of_user_1_one_on_ones, :user_1_one_on_ones
  count :count_of_user_2_one_on_ones, :user_2_one_on_ones
end

calculations do
  calculate :whatever_this_is_called, :integer, expr(count_of_user_1_one_on_ones - count_of_user_2_one_on_ones)
end

relationships do
  has_many :user_1_one_on_ones, Mod.OneOnOne do
    destination_attribute :user_1_id
  end

  has_many :user_2_one_on_ones, Mod.OneOnOne do
    destination_attribute :user_2_id
  end
end

aggregates do
  count :count_of_user_1_one_on_ones, :user_1_one_on_ones
  count :count_of_user_2_one_on_ones, :user_2_one_on_ones
end

calculations do
  calculate :whatever_this_is_called, :integer, expr(count_of_user_1_one_on_ones - count_of_user_2_one_on_ones)
end

🪄 :magic_sparkles:

dj_gokuOP•3y ago

AHHH expr(count_of_user_1_one_on_ones - count_of_user_2_one_on_ones) Well it is the combination of the aggregates and calculation!

ZachDaniel•3y ago

Yep 🙂 The equivalent "manual" calculation would look like this:

defmodule YourCalc do
  use Ash.Calculation

  def load(_, _, _) do
    [:count_of_user_1_one_on_ones, :count_of_user_2_one_on_ones]
  end

  def calculate(users, _, _) do
    {:ok, Enum.map(users, fn user -> 
      user.count_of_user_1_one_on_ones - user.count_of_user_2_one_on_ones
    end)}
  end
end

defmodule YourCalc do
  use Ash.Calculation

  def load(_, _, _) do
    [:count_of_user_1_one_on_ones, :count_of_user_2_one_on_ones]
  end

  def calculate(users, _, _) do
    {:ok, Enum.map(users, fn user -> 
      user.count_of_user_1_one_on_ones - user.count_of_user_2_one_on_ones
    end)}
  end
end

Then you could say calculate :whatever_this_is_called, :integer, YourCalc But, when you can use expr/1, you should. Just showing how it might be done if you have something super custom you want to do.

dj_gokuOP•3y ago

Ok, thanks! That is what I thought it would be! Phew. I think I am done. I'll share once I am done with this little project. Have a good rest of your day/night Zach!

ZachDaniel•3y ago

Thanks, you as well!

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Calculate aggregations?

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