How to do bulk inserts in ash json api

We don’t currently have tools to automatically build bulk action endpoints (although I’d very much like to do this).

So for this you’d need to define a generic action

defmodule YourCustomMapTypeOfFields do
  use Ash.Type.NewType, subtype_of: :map, constraints: [
    fields: [
     field1: [type: :integer, ...]
     ....
    ]
  ]
end

action :bulk_create, {:array, __MODULE__} do
  argument :inputs, {:array, YourCustomMapTypeOfFields}, allow_nil?: false

  run fn input, _ ->
    # use Ash.bulk_create with `input.arguments.inputs` 
  end
end

Then you can use route/3 to make a generic action route:

route :post, "/path/to/your/route", :bulk_create

When I try to apply your solution, I get a runtime error saying that MODULE is not a valid type. The error message mentions that valid types include any custom types or the following short codes (alongside the types they map to). Do I need to specify my return type as the custom Ash type module?

Ah, sorry about that

action :bulk_create, {:array, :struct} do
  constraints [items: [instance_of: __MODULE__]]
  argument :inputs, {:array, YourCustomMapTypeOfFields}, allow_nil?: false

  run fn input, _ ->
    # use Ash.bulk_create with `input.arguments.inputs` 
  end
end