add unique index to collections

app/controllers/v1/collections_controller.rb

@@ -7,7 +7,7 @@ class V1::CollectionsController < ApplicationController
   include ::Paginator
 
 
-  before_action :set_collection, only: [:show, :update, :destroy, :add_object]
+  before_action :set_collection, only: [:show, :update, :destroy, :add_object, :set_collection_items]
   before_action :authenticate_user!, only: [:create, :update, :destroy]
 
   # GET /v1/collections
@@ -27,6 +27,7 @@ class V1::CollectionsController < ApplicationController
   # POST /v1/collection.json
   def create
     collection = Collection.new(collection_params)
+    set_collection_items
 
     if collection.save
       render json: collection, status: :created
@@ -38,6 +39,9 @@ class V1::CollectionsController < ApplicationController
   # PUT/PATCH /v1/users/1
   # PUT/PATCH /v1/users/1.json
   def update
+
+    set_collection_items
+
     if @collection.update(collection_params)
       render json: @collection, status: :ok
     else
@@ -55,19 +59,7 @@ class V1::CollectionsController < ApplicationController
   # POST /v1/collections/!/items
   def add_object
     render nothing: true, status: :unprocessable_entity if params.nil?
-
-    items = collection_params[:items]
-
-    items.each do |item|
-      order = item[:order]
-      item = item[:type].constantize.find(item[:id])
-      collection_item = { collection: @collection, collectionable: item, order: order }
-
-      collection_item = CollectionItem.new(collection_item)
-
-      collection_item.save
-    end
-
+    set_collection_items
     render json: @collection, status: :ok
   end
 
@@ -85,6 +77,14 @@ class V1::CollectionsController < ApplicationController
     @collection ||= Collection.find(params[:id])
   end
 
+  def set_collection_items
+    items = collection_params[:items]
+    collection_items = items.map{ |item| CollectionItem.new(collection: @collection,
+                                                            collectionable: item[:type].constantize.find(item[:id]),
+                                                            order: item[:order])}
+    CollectionItem.import collection_items, on_duplicate_key_update: {conflict_target: [:collection_id, :collectionable_id, :collectionable_type]}
+  end
+
   # Never trust parameters from the scary internet, only allow the white list through.
   def collection_params
     params.require(:collection).permit(:name, :description, :owner_id, :owner_type, :privacy, tags: [], items: [:type, :id])

db/migrate/20161018123459_add_index_to_collection.rb

+class AddIndexToCollection < ActiveRecord::Migration[5.0]
+  def change
+    add_index :collection_items, [:collection_id,:collectionable_id, :collectionable_type], unique: true, name: 'collection_item_and_collectionable'
+  end
+end