Make User.following a postgres array.

priv/repo/migrations/20180221210540_make_following_postgres_array.exs

@@ -0,0 +1,18 @@
+defmodule Pleroma.Repo.Migrations.MakeFollowingPostgresArray do
+  use Ecto.Migration
+
+  def change do
+    alter table(:users) do
+      add :following_temp, {:array, :string}
+    end
+
+    execute """
+    update users set following_temp = array(select jsonb_array_elements_text(following));
+    """
+
+    alter table(:users) do
+      remove :following
+    end
+    rename table(:users), :following_temp, to: :following
+  end
+end