Set ltree column’s default value to ""(blank string)

Author: fahchen

priv/repo/migrations/20180625095801_create_catelogs.exs

@@ -7,7 +7,7 @@ defmodule Dummy.Repo.Migrations.CreateCatelogs do
     create table(:catelogs, primary_key: false) do
       add :id, :uuid, primary_key: true
       add :name, :string
-      add :path, :ltree, null: false
+      add :path, :ltree, null: false, default: ""
 
       timestamps()
     end