IDENTITY opt-in config Issue: #233

.formatter.exs

@@ -18,6 +18,7 @@ spark_locals_without_parens = [
   error_fields: 1,
   exclusion_constraint_names: 1,
   foreign_key_names: 1,
+  identity_column_defaults: 1,
   identity_index_names: 1,
   identity_wheres_to_sql: 1,
   ignore?: 1,

lib/data_layer.ex

@@ -406,6 +406,13 @@ defmodule AshPostgres.DataLayer do
         doc: """
         Options passed to ecto's table/2 in the create migration. See the [Ecto.Migration.table/2](https://hexdocs.pm/ecto_sql/Ecto.Migration.html#table/2) documentation for more information.
         """
+      ],
+      identity_column_defaults: [
+        type: {:list, :atom},
+        default: [],
+        doc: """
+        A list of attribute names that should use `GENERATED BY DEFAULT AS IDENTITY` instead of `SERIAL`/`BIGSERIAL` in migrations. Use for `integer_primary_key` and other generated integer columns. Opt-in until the next major release.
+        """
       ]
     ]
   }

lib/data_layer/info.ex

@@ -231,4 +231,9 @@ defmodule AshPostgres.DataLayer.Info do
   def create_table_options(resource) do
     Extension.get_opt(resource, [:postgres], :create_table_options, nil)
   end
+
+  @doc "Attributes that should use IDENTITY instead of SERIAL/BIGSERIAL in migrations"
+  def identity_column_defaults(resource) do
+    Extension.get_opt(resource, [:postgres], :identity_column_defaults, [])
+  end
 end

lib/migration_generator/migration_generator.ex

@@ -3759,6 +3759,16 @@ defmodule AshPostgres.MigrationGenerator do
           type
         end
 
+      identity_column_defaults = AshPostgres.DataLayer.Info.identity_column_defaults(resource)
+      source = attribute.source || attribute.name
+
+      type =
+        if source in identity_column_defaults and attribute.generated? and type in [:bigint, :integer] do
+          :identity
+        else
+          type
+        end
+
       {type, size, precision, scale} =
         migration_type_to_type(type)
 

lib/migration_generator/operation.ex

@@ -77,13 +77,11 @@ defmodule AshPostgres.MigrationGenerator.Operation do
       :bigint
     end
 
-    def reference_type(%{type: :integer, default: "nil", generated?: true}, _) do
-      ":bigserial"
-    end
+    def reference_type(%{type: :identity}, _), do: ":identity"
 
-    def reference_type(%{type: type}, _) do
-      type
-    end
+    def reference_type(%{type: :integer, default: "nil", generated?: true}, _), do: ":bigserial"
+
+    def reference_type(%{type: type}, _), do: type
 
     def with_match(reference, source_attribute \\ nil)
 
@@ -489,6 +487,16 @@ defmodule AshPostgres.MigrationGenerator.Operation do
       |> join()
     end
 
+    def up(%{attribute: %{type: :identity} = attribute}) do
+      [
+        "add #{inspect(attribute.source)}",
+        ":identity",
+        maybe_add_null(attribute.allow_nil?),
+        maybe_add_primary_key(attribute.primary_key?)
+      ]
+      |> join()
+    end
+
     def up(%{attribute: %{type: :bigint, default: "nil", generated?: true} = attribute}) do
       [
         "add #{inspect(attribute.source)}",
@@ -659,10 +667,14 @@ defmodule AshPostgres.MigrationGenerator.Operation do
              Map.get(old_attribute, :references) != Map.get(attribute, :references) do
           reference(multitenancy, attribute, schema)
         else
-          if attribute.type == :bigint and attribute.default == "nil" and attribute.generated? do
-            ":bigserial"
+          if attribute.type == :identity do
+            ":identity"
           else
-            inspect(attribute.type)
+            if attribute.type == :bigint and attribute.default == "nil" and attribute.generated? do
+              ":bigserial"
+            else
+              inspect(attribute.type)
+            end
           end
         end
 

lib/resource_generator/spec.ex

@@ -956,6 +956,7 @@ defmodule AshPostgres.ResourceGenerator.Spec do
 
   defp type("bigint"), do: {:ok, :integer}
   defp type("bigserial"), do: {:ok, :integer}
+  defp type("identity"), do: {:ok, :identity}
   defp type("boolean"), do: {:ok, :boolean}
   defp type("bytea"), do: {:ok, :binary}
   defp type("varchar"), do: {:ok, :string}