Propagate the caller's Logger level to preload tasks

lib/ecto/repo/preloader.ex

@@ -159,10 +159,12 @@ defmodule Ecto.Repo.Preloader do
       # still necessary.
       opts = Keyword.put_new(opts, :caller, self())
       on_preloader_spawn = Keyword.get(opts, :on_preloader_spawn, fn -> :ok end)
+      log_level = caller_log_level()
 
       preloaders
       |> Task.async_stream(
         fn preloader ->
+          put_log_level(log_level)
           on_preloader_spawn.()
           preloader.({adapter_meta, opts})
         end,
@@ -177,6 +179,16 @@ defmodule Ecto.Repo.Preloader do
     end
   end
 
+  # Logger.get_process_level/1 and put_process_level/2 require Elixir 1.15+.
+  if Version.match?(System.version(), ">= 1.15.0") do
+    defp caller_log_level, do: Logger.get_process_level(self())
+    defp put_log_level(nil), do: :ok
+    defp put_log_level(level), do: Logger.put_process_level(self(), level)
+  else
+    defp caller_log_level, do: nil
+    defp put_log_level(_level), do: :ok
+  end
+
   # Then we unpack the query results, merge them, and preload recursively
   defp preload_assocs(
          [{assoc, query?, loaded_ids, loaded_structs, sub_preloads} | assocs],

test/ecto/repo_test.exs

@@ -2382,6 +2382,23 @@ defmodule Ecto.RepoTest do
       assert_received {:callback_ran, pid2} when pid2 != self()
       assert pid1 != pid2
     end
+
+    # Logger.{put,get,delete}_process_level were added in Elixir 1.15.
+    if Version.match?(System.version(), ">= 1.15.0") do
+      test "preload tasks inherit the caller's Logger level" do
+        Logger.put_process_level(self(), :warning)
+        on_exit(fn -> Logger.delete_process_level(self()) end)
+
+        test_process = self()
+        fun = fn -> send(test_process, {:level, Logger.get_process_level(self())}) end
+
+        %MySchemaWithMultiAssoc{parent_id: 1, mother_id: 2}
+        |> PrepareRepo.preload([:parent, :mother], on_preloader_spawn: fun)
+
+        assert_received {:level, :warning}
+        assert_received {:level, :warning}
+      end
+    end
   end
 
   describe "prepare_transaction" do