Behaviour for schema migration modules loaded from priv/migrations.

Schema files are optional Elixir modules that return CQL statements from change/0. They can return raw CQL strings or structured %AshScylla.Schema{} entries organised by domain and resource.

Struct-based schema (generated by mix ash_scylla.gen)

defmodule MyApp.Migrations.Schema20260615155440 do
  use AshScylla.Schema

  def change do
    [
      %AshScylla.Schema{
        domain: MyApp.Domain,
        resources: [
          %AshScylla.Schema.Resource{
            name: :users,
            statements: [
              "CREATE TABLE IF NOT EXISTS users (id UUID PRIMARY KEY, name TEXT)",
              "CREATE INDEX IF NOT EXISTS idx_users_email ON users (email)"
            ]
          }
        ]
      }
    ]
  end
end

Flat CQL list (hand-written)

defmodule MyApp.Migrations.AddUserTable do
  use AshScylla.Schema

  def change do
    [
      "CREATE TABLE IF NOT EXISTS users (id UUID PRIMARY KEY, name TEXT)"
    ]
  end
end

Flattening

flatten/1 converts a mixed list of CQL strings and %AshScylla.Schema{} structs into a flat list of CQL strings for execution.