Remove unnecessary indexes

db/migrate/20170926203418_create_board_labels.rb

@@ -5,8 +5,8 @@ class CreateBoardLabels < ActiveRecord::Migration
 
   def change
     create_table :board_labels do |t|
-      t.references :board, index: true, foreign_key: { on_delete: :cascade }, null: false
-      t.references :label, index: true, foreign_key: { on_delete: :cascade }, null: false
+      t.references :board, foreign_key: { on_delete: :cascade }, null: false
+      t.references :label, foreign_key: { on_delete: :cascade }, null: false
       t.index [:board_id, :label_id], unique: true
     end
   end

db/migrate/20171010095526_create_board_assignees.rb

@@ -5,8 +5,8 @@ class CreateBoardAssignees < ActiveRecord::Migration
 
   def change
     create_table :board_assignees do |t|
-      t.references :board, index: true, foreign_key: { on_delete: :cascade }, null: false
-      t.integer :assignee_id, null: false, index: true
+      t.references :board, foreign_key: { on_delete: :cascade }, null: false
+      t.integer :assignee_id, null: false
       t.foreign_key :users, column: :assignee_id, on_delete: :cascade
       t.index [:board_id, :assignee_id], unique: true
     end

db/schema.rb

@@ -219,9 +219,7 @@ ActiveRecord::Schema.define(version: 20171010140746) do
     t.integer "assignee_id", null: false
   end
 
-  add_index "board_assignees", ["assignee_id"], name: "index_board_assignees_on_assignee_id", using: :btree
   add_index "board_assignees", ["board_id", "assignee_id"], name: "index_board_assignees_on_board_id_and_assignee_id", unique: true, using: :btree
-  add_index "board_assignees", ["board_id"], name: "index_board_assignees_on_board_id", using: :btree
 
   create_table "board_labels", force: :cascade do |t|
     t.integer "board_id", null: false
@@ -229,8 +227,6 @@ ActiveRecord::Schema.define(version: 20171010140746) do
   end
 
   add_index "board_labels", ["board_id", "label_id"], name: "index_board_labels_on_board_id_and_label_id", unique: true, using: :btree
-  add_index "board_labels", ["board_id"], name: "index_board_labels_on_board_id", using: :btree
-  add_index "board_labels", ["label_id"], name: "index_board_labels_on_label_id", using: :btree
 
   create_table "boards", force: :cascade do |t|
     t.integer "project_id"