Ash Elixir•2y ago

Issues using Ash.Type.Union

So I'm trying to use Ash.Type.Union and I keep getting errors when attempting to load the resource, I have defined an embedded resource

defmodule VMX.Transactions.TransactionData.Type.Call do
  use Ash.Resource, data_layer: :embedded

  attributes do
    attribute :call_uuid, :string
    attribute :plivo_recording_url, :string
    attribute :receiver, :string
    attribute :recording_duration, :string
    attribute :recording_url, :string
    attribute :recording_uuid, :string
    attribute :sender, :string
  end
end

defmodule VMX.Transactions.TransactionData.Type.Call do
  use Ash.Resource, data_layer: :embedded

  attributes do
    attribute :call_uuid, :string
    attribute :plivo_recording_url, :string
    attribute :receiver, :string
    attribute :recording_duration, :string
    attribute :recording_url, :string
    attribute :recording_uuid, :string
    attribute :sender, :string
  end
end

22 Replies

kernelOP•2y ago

the parent resource has this data in the attribute which is a union type

%{"__schema": "call", "call_uuid" => "9ba4f656-e85f-11ec-827b-8f363c318b4c", "plivo_recording_url" => "some.mp3", "receiver" => "122345674", "recording_duration" => "21240", "recording_url" => "meow.mp3", "recording_uuid" => "f67797ef-3fb7-4dc7-819d-46b905e6230f", "sender" => "1234567"}

%{"__schema": "call", "call_uuid" => "9ba4f656-e85f-11ec-827b-8f363c318b4c", "plivo_recording_url" => "some.mp3", "receiver" => "122345674", "recording_duration" => "21240", "recording_url" => "meow.mp3", "recording_uuid" => "f67797ef-3fb7-4dc7-819d-46b905e6230f", "sender" => "1234567"}

and the parent resource attribute is defined as such

attribute :data, :union do
      constraints types: [
                    call: [
                      type: __MODULE__.Type.Call,
                      tag: :__schema,
                      tag_value: :call
                    ]
                  ]
    end

attribute :data, :union do
      constraints types: [
                    call: [
                      type: __MODULE__.Type.Call,
                      tag: :__schema,
                      tag_value: :call
                    ]
                  ]
    end

I get this error when tryig to load

[error] GenServer #PID<0.1133.0> terminating
** (Ash.Error.Unknown) Unknown Error

* ** (ArgumentError) cannot load <<the json>> as type #Ash.Type.Union.EctoType<[types: [call: [type: VMX.Transactions.TransactionData.Type.Call, constraints: [], tag: :type, tag_value: :call], email: [type: VMX.Transactions.TransactionData.Type.Email, constraints: [], tag: :type, tag_value: :email]]]> for field :data in #VMX.Transactions.TransactionData<transaction: #Ash.NotLoaded<:relationship>, __meta__: #Ecto.Schema.Metadata<:loaded, "transaction_datum">, type: nil, data: nil, transaction_id: nil, aggregates: %{}, calculations: %{}, ...>

[error] GenServer #PID<0.1133.0> terminating
** (Ash.Error.Unknown) Unknown Error

* ** (ArgumentError) cannot load <<the json>> as type #Ash.Type.Union.EctoType<[types: [call: [type: VMX.Transactions.TransactionData.Type.Call, constraints: [], tag: :type, tag_value: :call], email: [type: VMX.Transactions.TransactionData.Type.Email, constraints: [], tag: :type, tag_value: :email]]]> for field :data in #VMX.Transactions.TransactionData<transaction: #Ash.NotLoaded<:relationship>, __meta__: #Ecto.Schema.Metadata<:loaded, "transaction_datum">, type: nil, data: nil, transaction_id: nil, aggregates: %{}, calculations: %{}, ...>

Am I doing something obviously wrong or? cast_input works

barnabasj•2y ago

how did you save the data using ash or are you trying to load existing data from the database? Ash persists the data wraped inside union type like so:

{ type: "the type of the union", value: {"your": "data"} }

{ type: "the type of the union", value: {"your": "data"} }

so if you're trying to load existing data that's just the json, that won't work because it expects the format from above

kernelOP•2y ago

ah right yeah I'm trying to load existing data 🙂 which is just json hmmm :thinkies:

barnabasj•2y ago

In that case you probably have to migrate it first, into a different column or something, load it as map, and persist it as ash union

kernelOP•2y ago

that sounds like a lot of work why does ash choose to save stuff that way tbh? I would have thought just plain would be enough

barnabasj•2y ago

not sure, tbh. have to wait for zach to answer that 😉

kernelOP•2y ago

performs the ritual to summon zach daniel leinad hcaz, leinad hcaz, leinad hcaz

barnabasj•2y ago

Depending on how much data you have you could just do something like this for the migration

Resource
|> Ash.Query.for_read(:paginated)
|> Api.stream!()
|> Enum.each(fn resource ->
  resource
  |> Ash.Changeset.for_update(:update, %{union_attribute: resource.map_attribute})
  |> Api.update!()
end)

Resource
|> Ash.Query.for_read(:paginated)
|> Api.stream!()
|> Enum.each(fn resource ->
  resource
  |> Ash.Changeset.for_update(:update, %{union_attribute: resource.map_attribute})
  |> Api.update!()
end)

kernelOP•2y ago

only a few million rows 😆 could do it with a db query I guess I'll migrate the data for now into Ash's format I dont necessarily like it, but it may be for a good reason maybe Zach can enlighten me as to why it was chosen to be saved like that, as opposed to just raw json with the type tag not being made into an attribute, or why the type tag wasn't able to be on the resource containing the union type (probably easier and more portable to have it tied to the type) when you say this, do you mean type is the configured type tag? i.e: for me it would be {"__schema": "call", "value": {...}}

barnabasj•2y ago

I think it is the key for you type, which is the same in your case

types: [
  # the typename should be the type in the union struct
  typename: [
    config...

types: [
  # the typename should be the type in the union struct
  typename: [
    config...

But unions have been more trial and error for me than really understanding so far tbh 😅

kernelOP•2y ago

yeah it's type

kernelOP•2y ago

works

kernelOP•2y ago

mmm I don't know if I like this 😜 , it feels like 'application level' stuff starting to dictate how I do my database at least it's just a type tag, it would be terrible if it was saving the actual module name of my type 🤣 thanks @barnabasj 🙂

ZachDaniel•2y ago

We can make this configurable potentially 🙂 The main reason is that you can’t always tell what type something is when loading from the database. Like a value may be valid for multiple types But when saving, we selected one. It would be as easy as adding a constraint to the type TBH

kernelOP•2y ago

personally I would like something that either has the type in the actual json - or something with the type tag on the resource, so in my case I can say this is transaction data for a 'email' transaction or a 'call' transaction and the type can just be a FK to the transactions table and if it's in the json, I would just something like this in json

{__type: 'email', ...restOfData}

{__type: 'email', ...restOfData}

ZachDaniel•2y ago

Yeah, that makes sense, but only for some unions i.e a union of only objects it works

kernelOP•2y ago

yeah hadn't thought of the others 🙂

ZachDaniel•2y ago

But still, we could make these storage options a constraint with little-to-no hassle 🙂 Can you make a GH issue describing the behavior you’d want to get out of your unions? Changing the underlying storage of unions is easy.

kernelOP•2y ago

it would be opt-in right? just because unions are already out in the wild

kernelOP•2y ago

https://github.com/ash-project/ash/issues/694

GitHub

configurable storage for union type · Issue #694 · ash-project/ash

Following on from our conversations on Discord, it would be helpful to be able to configure a simpler storage type for the union type. Ideally we would just store the json directly in the database ...

kernelOP•2y ago

there we go

ZachDaniel•2y ago

Yep! It would be opt-in 👍

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Issues using Ash.Type.Union

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