improvement: set lateral join source for latest ash

improvement: use `prepend?: true` option when applying relationship sorts

lib/data_layer.ex

@@ -810,7 +810,7 @@ defmodule AshPostgres.DataLayer do
     |> Ash.Query.new()
     |> Ash.Query.set_context(through_relationship.context)
     |> Ash.Query.do_filter(through_relationship.filter)
-    |> Ash.Query.sort(through_relationship.sort)
+    |> Ash.Query.sort(through_relationship.sort, prepend?: true)
     |> Ash.Query.set_tenant(source_query.tenant)
     |> set_lateral_join_prefix(query)
     |> case do
@@ -849,13 +849,15 @@ defmodule AshPostgres.DataLayer do
                         source_query,
                         relationship.through
                       ),
-                    as: ^1,
                     on:
                       field(through, ^destination_attribute_on_join_resource) ==
                         field(destination, ^destination_attribute),
                     where:
                       field(through, ^source_attribute_on_join_resource) ==
-                        field(parent_as(^0), ^source_attribute)
+                        field(parent_as(^0), ^source_attribute),
+                    select_merge: %{
+                      __lateral_join_source__: field(through, ^source_attribute_on_join_resource)
+                    }
                   )
                   |> set_subquery_prefix(
                     source_query,
@@ -882,13 +884,15 @@ defmodule AshPostgres.DataLayer do
                         source_query,
                         relationship.through
                       ),
-                    as: ^1,
                     on:
                       field(through, ^destination_attribute_on_join_resource) ==
                         field(destination, ^destination_attribute),
                     where:
                       field(through, ^source_attribute_on_join_resource) ==
-                        field(parent_as(^0), ^source_attribute)
+                        field(parent_as(^0), ^source_attribute),
+                    select_merge: %{
+                      __lateral_join_source__: field(through, ^source_attribute_on_join_resource)
+                    }
                   )
                   |> set_subquery_prefix(
                     source_query,

test/load_test.exs

@@ -174,5 +174,52 @@ defmodule AshPostgres.Test.LoadTest do
 
       assert %{linked_posts: [%{title: "abc"}, %{title: "def"}]} = results
     end
+
+    test "lateral join loads with many to many relationships are supported with aggregates" do
+      source_post =
+        Post
+        |> Ash.Changeset.new(%{title: "source"})
+        |> Api.create!()
+
+      destination_post =
+        Post
+        |> Ash.Changeset.new(%{title: "abc"})
+        |> Api.create!()
+
+      destination_post2 =
+        Post
+        |> Ash.Changeset.new(%{title: "def"})
+        |> Api.create!()
+
+      source_post
+      |> Ash.Changeset.new()
+      |> Ash.Changeset.manage_relationship(:linked_posts, [destination_post, destination_post2],
+        type: :append_and_remove
+      )
+      |> Api.update!()
+
+      linked_posts_query =
+        Post
+        |> Ash.Query.limit(1)
+        |> Ash.Query.sort(title: :asc)
+
+      results =
+        source_post
+        |> Api.load!(linked_posts: linked_posts_query)
+
+      assert %{linked_posts: [%{title: "abc"}]} = results
+
+      linked_posts_query =
+        Post
+        |> Ash.Query.limit(2)
+        |> Ash.Query.sort(title: :asc)
+        |> Ash.Query.filter(count_of_comments_called_match == 0)
+
+      results =
+        source_post
+        |> Api.load!(linked_posts: linked_posts_query)
+
+      assert %{linked_posts: [%{title: "abc"}, %{title: "def"}]} = results
+    end
   end
 end

test/support/resources/post_link.ex

@@ -12,6 +12,10 @@ defmodule AshPostgres.Test.PostLink do
     defaults([:create, :read, :update, :destroy])
   end
 
+  identities do
+    identity(:unique_link, [:source_post_id, :destination_post_id])
+  end
+
   relationships do
     belongs_to :source_post, AshPostgres.Test.Post do
       allow_nil?(false)