Simplify migration and add NOT NULL to project_id.

db/migrate/20180305095250_create_internal_ids_table.rb

@@ -3,33 +3,17 @@ class CreateInternalIdsTable < ActiveRecord::Migration
 
   DOWNTIME = false
 
-  disable_ddl_transaction!
-
   def up
     create_table :internal_ids, id: :bigserial do |t|
-      t.references :project
+      t.references :project, null: false, foreign_key: { on_delete: :cascade }
       t.integer :usage, null: false
       t.integer :last_value, null: false
-    end
-
-    unless index_exists?(:internal_ids, [:usage, :project_id])
-      add_index :internal_ids, [:usage, :project_id], unique: true
-    end
 
-    unless foreign_key_exists?(:internal_ids, :project_id)
-      add_concurrent_foreign_key :internal_ids, :projects, column: :project_id, on_delete: :cascade
+      t.index [:usage, :project_id], unique: true
     end
   end
 
   def down
     drop_table :internal_ids
   end
-
-  private
-
-  def foreign_key_exists?(table, column)
-    foreign_keys(table).any? do |key|
-      key.options[:column] == column.to_s
-    end
-  end
 end

db/schema.rb

@@ -867,7 +867,7 @@ ActiveRecord::Schema.define(version: 20180309160427) do
   add_index "identities", ["user_id"], name: "index_identities_on_user_id", using: :btree
 
   create_table "internal_ids", id: :bigserial, force: :cascade do |t|
-    t.integer "project_id"
+    t.integer "project_id", null: false
     t.integer "usage", null: false
     t.integer "last_value", null: false
   end
@@ -2066,7 +2066,7 @@ ActiveRecord::Schema.define(version: 20180309160427) do
   add_foreign_key "gpg_signatures", "gpg_keys", on_delete: :nullify
   add_foreign_key "gpg_signatures", "projects", on_delete: :cascade
   add_foreign_key "group_custom_attributes", "namespaces", column: "group_id", on_delete: :cascade
-  add_foreign_key "internal_ids", "projects", name: "fk_f7d46b66c6", on_delete: :cascade
+  add_foreign_key "internal_ids", "projects", on_delete: :cascade
   add_foreign_key "issue_assignees", "issues", name: "fk_b7d881734a", on_delete: :cascade
   add_foreign_key "issue_assignees", "users", name: "fk_5e0c8d9154", on_delete: :cascade
   add_foreign_key "issue_metrics", "issues", on_delete: :cascade