1 files changed, 26 insertions, 17 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 22f6f5e7d6..daf4113b66 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -105,7 +105,7 @@ class CreateOrders < ActiveRecord::Migration
     end
 
     create_table :orders do |t|
-      t.belongs_to :customer
+      t.belongs_to :customer, index: true
       t.datetime :order_date
       t.timestamps
     end
@@ -136,7 +136,7 @@ class CreateSuppliers < ActiveRecord::Migration
     end
 
     create_table :accounts do |t|
-      t.belongs_to :supplier
+      t.belongs_to :supplier, index: true
       t.string :account_number
       t.timestamps
     end
@@ -169,7 +169,7 @@ class CreateCustomers < ActiveRecord::Migration
     end
 
     create_table :orders do |t|
-      t.belongs_to :customer
+      t.belongs_to :customer, index:true
       t.datetime :order_date
       t.timestamps
     end
@@ -216,8 +216,8 @@ class CreateAppointments < ActiveRecord::Migration
     end
 
     create_table :appointments do |t|
-      t.belongs_to :physician
-      t.belongs_to :patient
+      t.belongs_to :physician, index: true
+      t.belongs_to :patient, index: true
       t.datetime :appointment_date
       t.timestamps
     end
@@ -295,13 +295,13 @@ class CreateAccountHistories < ActiveRecord::Migration
     end
 
     create_table :accounts do |t|
-      t.belongs_to :supplier
+      t.belongs_to :supplier, index: true
       t.string :account_number
       t.timestamps
     end
 
     create_table :account_histories do |t|
-      t.belongs_to :account
+      t.belongs_to :account, index: true
       t.integer :credit_rating
       t.timestamps
     end
@@ -341,8 +341,8 @@ class CreateAssembliesAndParts < ActiveRecord::Migration
     end
 
     create_table :assemblies_parts, id: false do |t|
-      t.belongs_to :assembly
-      t.belongs_to :part
+      t.belongs_to :assembly, index: true
+      t.belongs_to :part, index: true
     end
   end
 end
@@ -379,6 +379,8 @@ class CreateSuppliers < ActiveRecord::Migration
       t.string  :account_number
       t.timestamps
     end
+
+    add_index :accounts, :supplier_id
   end
 end
 ```
@@ -455,6 +457,8 @@ class CreatePictures < ActiveRecord::Migration
       t.string  :imageable_type
       t.timestamps
     end
+
+    add_index :pictures, :imageable_id
   end
 end
 ```
@@ -466,7 +470,7 @@ class CreatePictures < ActiveRecord::Migration
   def change
     create_table :pictures do |t|
       t.string :name
-      t.references :imageable, polymorphic: true
+      t.references :imageable, polymorphic: true, index: true
       t.timestamps
     end
   end
@@ -496,7 +500,7 @@ In your migrations/schema, you will add a references column to the model itself.
 class CreateEmployees < ActiveRecord::Migration
   def change
     create_table :employees do |t|
-      t.references :manager
+      t.references :manager, index: true
       t.timestamps
     end
   end
@@ -561,6 +565,8 @@ class CreateOrders < ActiveRecord::Migration
       t.string   :order_number
       t.integer  :customer_id
     end
+
+    add_index :orders, :customer_id
   end
 end
 ```
@@ -594,6 +600,9 @@ class CreateAssembliesPartsJoinTable < ActiveRecord::Migration
       t.integer :assembly_id
       t.integer :part_id
     end
+
+    add_index :assemblies_parts, :assembly_id
+    add_index :assemblies_parts, :part_id
   end
 end
 ```
@@ -1131,7 +1140,7 @@ The `has_one` association supports these options:
 
 ##### `:as`
 
-Setting the `:as` option indicates that this is a polymorphic association. Polymorphic associations were discussed in detail <a href="#polymorphic-associations">earlier in this guide</a>.
+Setting the `:as` option indicates that this is a polymorphic association. Polymorphic associations were discussed in detail [earlier in this guide](#polymorphic-associations).
 
 ##### `:autosave`
 
@@ -1203,7 +1212,7 @@ The `:source_type` option specifies the source association type for a `has_one :
 
 ##### `:through`
 
-The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail <a href="#the-has-one-through-association">earlier in this guide</a>.
+The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail [earlier in this guide](#the-has-one-through-association).
 
 ##### `:validate`
 
@@ -1497,7 +1506,7 @@ The `has_many` association supports these options:
 
 ##### `:as`
 
-Setting the `:as` option indicates that this is a polymorphic association, as discussed <a href="#polymorphic-associations">earlier in this guide</a>.
+Setting the `:as` option indicates that this is a polymorphic association, as discussed [earlier in this guide](#polymorphic-associations).
 
 ##### `:autosave`
 
@@ -1579,7 +1588,7 @@ The `:source_type` option specifies the source association type for a `has_many
 
 ##### `:through`
 
-The `:through` option specifies a join model through which to perform the query. `has_many :through` associations provide a way to implement many-to-many relationships, as discussed <a href="#the-has-many-through-association">earlier in this guide</a>.
+The `:through` option specifies a join model through which to perform the query. `has_many :through` associations provide a way to implement many-to-many relationships, as discussed [earlier in this guide](#the-has-many-through-association).
 
 ##### `:validate`
 
@@ -1632,7 +1641,7 @@ If you use a hash-style `where` option, then record creation via this associatio
 
 ##### `extending`
 
-The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail <a href="#association-extensions">later in this guide</a>.
+The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail [later in this guide](#association-extensions).
 
 ##### `group`
 
@@ -2082,7 +2091,7 @@ If you use a hash-style `where`, then record creation via this association will
 
 ##### `extending`
 
-The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail <a href="#association-extensions">later in this guide</a>.
+The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail [later in this guide](#association-extensions).
 
 ##### `group`