Fix N+1 problem

app/controllers/microposts_controller.rb

@@ -22,7 +22,7 @@ def destroy
 
   def search
     @micropost  = current_user.microposts.build
-    @feed_items = Micropost.content_like(params[:content]).page params[:page]
+    @feed_items = Micropost.includes(:user).content_like(params[:content]).page params[:page]
   end
 
   def likes

app/models/user.rb

@@ -71,10 +71,8 @@ def password_reset_expired?
   end
 
   def feed
-    following_ids = "SELECT followed_id FROM relationships
-                     WHERE follower_id = :user_id"
-    Micropost.where("user_id IN (#{following_ids})
-                     OR user_id = :user_id", user_id: id)
+    following_ids = "SELECT followed_id FROM relationships WHERE follower_id = :user_id"
+    Micropost.includes(:user).where("user_id IN (#{following_ids}) OR user_id = :user_id", user_id: id)
   end
 
   def follow(other_user)
@@ -96,7 +94,7 @@ def send_followed_notification_email(user)
   def liked_microposts
     ids = []
     likes.each { |like| ids << like.micropost_id }
-    Micropost.where(id: ids)
+    Micropost.includes(:user).where(id: ids)
   end
 
   private

app/views/microposts/_micropost.html.haml

@@ -10,4 +10,4 @@
     = micropost.content
     = image_tag micropost.picture.url if micropost.picture?
   %span.like
-    = render 'likes/like_form', micropost: @micropost = micropost, users: @users = micropost.liked_users
+    = render 'likes/like_form', micropost: @micropost = micropost, users: @users = Micropost.includes(:likes).find(micropost.id).liked_users