diff --git a/priv/repo/migrations/20220711182322_add_associated_object_id_function.exs b/priv/repo/migrations/20220711182322_add_associated_object_id_function.exs
new file mode 100644
index 000000000..76348f31a
--- /dev/null
+++ b/priv/repo/migrations/20220711182322_add_associated_object_id_function.exs
@@ -0,0 +1,37 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Repo.Migrations.AddAssociatedObjectIdFunction do
+  use Ecto.Migration
+
+  def up do
+    statement = """
+    CREATE OR REPLACE FUNCTION associated_object_id(data jsonb) RETURNS varchar AS $$
+    DECLARE
+      object_data jsonb;
+    BEGIN
+      IF jsonb_typeof(data->'object') = 'array' THEN
+        object_data := data->'object'->0;
+      ELSE
+        object_data := data->'object';
+      END IF;
+
+      IF jsonb_typeof(object_data->'id') = 'string' THEN
+        RETURN object_data->>'id';
+      ELSIF jsonb_typeof(object_data) = 'string' THEN
+        RETURN object_data#>>'{}';
+      ELSE
+        RETURN NULL;
+      END IF;
+    END;
+    $$ LANGUAGE plpgsql IMMUTABLE;
+    """
+
+    execute(statement)
+  end
+
+  def down do
+    execute("DROP FUNCTION IF EXISTS associated_object_id(data jsonb)")
+  end
+end
diff --git a/test/pleroma/activity_test.exs b/test/pleroma/activity_test.exs
index b5bb4bafe..e38384c9c 100644
--- a/test/pleroma/activity_test.exs
+++ b/test/pleroma/activity_test.exs
@@ -278,4 +278,78 @@ defmodule Pleroma.ActivityTest do
 
     assert Repo.aggregate(Activity, :count, :id) == 2
   end
+
+  describe "associated_object_id() sql function" do
+    test "with json object" do
+      %{rows: [[object_id]]} =
+        Ecto.Adapters.SQL.query!(
+          Pleroma.Repo,
+          """
+          select associated_object_id('{"object": {"id":"foobar"}}'::jsonb);
+          """
+        )
+
+      assert object_id == "foobar"
+    end
+
+    test "with string object" do
+      %{rows: [[object_id]]} =
+        Ecto.Adapters.SQL.query!(
+          Pleroma.Repo,
+          """
+          select associated_object_id('{"object": "foobar"}'::jsonb);
+          """
+        )
+
+      assert object_id == "foobar"
+    end
+
+    test "with array object" do
+      %{rows: [[object_id]]} =
+        Ecto.Adapters.SQL.query!(
+          Pleroma.Repo,
+          """
+          select associated_object_id('{"object": ["foobar", {}]}'::jsonb);
+          """
+        )
+
+      assert object_id == "foobar"
+    end
+
+    test "invalid" do
+      %{rows: [[object_id]]} =
+        Ecto.Adapters.SQL.query!(
+          Pleroma.Repo,
+          """
+          select associated_object_id('{"object": {}}'::jsonb);
+          """
+        )
+
+      assert is_nil(object_id)
+    end
+
+    test "invalid object id" do
+      %{rows: [[object_id]]} =
+        Ecto.Adapters.SQL.query!(
+          Pleroma.Repo,
+          """
+          select associated_object_id('{"object": {"id": 123}}'::jsonb);
+          """
+        )
+
+      assert is_nil(object_id)
+    end
+
+    test "no object field" do
+      %{rows: [[object_id]]} =
+        Ecto.Adapters.SQL.query!(
+          Pleroma.Repo,
+          """
+          select associated_object_id('{}'::jsonb);
+          """
+        )
+
+      assert is_nil(object_id)
+    end
+  end
 end