path_column can be null

Author: fahchen

README.md

@@ -47,7 +47,7 @@ defmodule MyApp.Repo.Migrations.CreateCatelogs do
     create table(:catelogs, primary_key: false) do
       add :id, :uuid, primary_key: true # the primary key is UUID
       add :name, :string
-      add :path, :ltree, null: false, default: "" # Default value should to be `""`
+      add :path, :ltree
 
       timestamps()
     end

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, default: ""
+      add :path, :ltree
 
       timestamps()
     end

priv/repo/migrations/20180628144013_create_organizations.exs

@@ -6,7 +6,7 @@ defmodule Dummy.Repo.Migrations.CreateOrganizations do
 
     create table(:organizations) do
       add :name, :string
-      add :ancestry, :ltree, null: false, default: ""
+      add :ancestry, :ltree
     end
 
     create index(:organizations, [:ancestry], using: "GIST")

test/ltree_test.exs

@@ -27,7 +27,7 @@ defmodule Hierarch.LtreeTest do
     end
 
     test "returns blank string" do
-      assert Hierarch.LTree.parent_path("Top") == ""
+      assert Hierarch.LTree.parent_path("Top") == nil
     end
   end