agonzalezro

Help thinking in Ash domains & resources

Hi folks

TLDR; I have an idea explained at the end, but I am not sure that’s how I should be doing it in Ash.

I am trying to understand how my domains & resources should look like.

I have a domain Portofolio where I want to store Assets and the price of those Assets for a given date.

A simplified version of what I have is:

defmodule Portfolio.Asset do
  attributes do
    ...
    attribute :name, :string, allow_nil?: false
    ...
  end

  relationships do
    belongs_to :user, Accounts.User, allow_nil?: false
    has_many :snapshots, AssetSnapshot
  end
end

defmodule Portfolio.AssetSnapshot do
  attributes do
    ...
    attribute :amount, :decimal, allow_nil?: false
    create_timestamp :created_at
    ...
  end

  relationships do
    belongs_to :asset, Portfolio.Asset, allow_nil?: false
  end
end

With these resources I could “easily” get user.assets and then for each asset a asset.last_snapshot or even have a calculation in the Portfolio for it. But at the moment that I need a bit more flexibility getting, for example, the last year snapshots I think it will get complicated.

I was thinking in adding an intermediary Snapshot for the whole Portfolio and not for the asset that would be simply:

attributes do
  ...
  date :date
  ...
end

relationships do
  has_many :assets, Portfolio.Asset, allow_nil?: false
  has_many :asset_snapshots, Porfolio.AssetSnapshot, allow_nil?: false
end

This way the Snapshot just saves the date and I can easily query there and create some calculations.

In the past I did something similar with a JSONB and I think I could get a similar behaviour here with a :map but I am not sure that’s the Ash-way.

Any insight would be more than welcome!

3 comments

/ash #postgres #postgresql #database #ash-postgres #ash_postgres

0 210 3

2025-04-18 20:49:34 UTC

First Post!

agonzalezro

This is what I was thinking about when I talked about the JSONB:

diff --git a/lib/mcduck/accounts/user.ex b/lib/mcduck/accounts/user.ex
index 1c35cb5..7be6539 100644
--- a/lib/mcduck/accounts/user.ex
+++ b/lib/mcduck/accounts/user.ex
@@ -100,6 +100,7 @@ defmodule Mcduck.Accounts.User do
 
   relationships do
     has_many :assets, Mcduck.Portfolio.Asset
+    has_many :snapshots, Mcduck.Portfolio.Snapshot
   end
 
   identities do
diff --git a/lib/mcduck/portfolio/snapshot.ex b/lib/mcduck/portfolio/snapshot.ex
index 6427ca5..fbced4c 100644
--- a/lib/mcduck/portfolio/snapshot.ex
+++ b/lib/mcduck/portfolio/snapshot.ex
@@ -16,16 +16,32 @@ defmodule Mcduck.Portfolio.Snapshot do
   attributes do
     uuid_primary_key :id
 
-    attribute :amount, :decimal, allow_nil?: false
+    attribute :date, :date, allow_nil?: false
+
+    attribute :asset_snapshots, :map do
+      allow_nil? false
+
+      constraints fields: [
+                    asset_id: [
+                      type: :uuid,
+                      allow_nil?: false
+                    ],
+                    rate_id: [
+                      type: :string,
+                      allow_nil?: false
+                    ],
+                    amount: [
+                      type: :decimal,
+                      allow_nil?: false
+                    ]
+                  ]
+    end
 
     create_timestamp :created_at
     update_timestamp :updated_at
-
-    attribute :rates_id, :uuid
   end
 
   relationships do
-    belongs_to :asset, Mcduck.Portfolio.Asset, allow_nil?: false
-    belongs_to :rate, Mcduck.Money.Rates, allow_nil?: true
+    belongs_to :user, Mcduck.Accounts.User, allow_nil?: false
   end
 end

But I will need to validate that the asset_snapshot maps includes real data as I can’t use the reference. Same when I delete et al. It seems more like a workaround than a real solution.

WDYT?

Post #1

Last Post!

agonzalezro

So do you think that the two resources I have defined make sense for the kind of queries I want to do later?

In case I want to query between two dates, for example one year, I might end up with few hundreds of AssetSnapshots vs few dozens in the case of the Snapshot I shared later. Maybe it’s simply an early optimization and nothing to worry about yet.

Post #3