如何加速 Rails 控制器查询？

Question

My app seams to be getting bogged down. Can someone can help me optimize this controller code to run faster? Or point me in the right direction. I'm trying to display a list of customers which are defined by active is true and a list of potential customers which active is false. Archived customers are archived true. Thank you.

if current_user.manager?
  get_customers = Customer.where(:archived => false)
  @cc = get_customers.where(:active => true)
  @current_customers = @cc.where(:user_id => current_user.id)
  @count_current = @current_customers.count

  @pc = get_customers.where(:active => false)
  @potential_customers = @pc.where(:user_id => current_user.id)
  @count_potential = @potential_customers.count
end

How does this look for improving speed?

model

scope :not_archived, -> { where(:archived => false) }
  scope :current_customers, -> { where(:active => true).not_archived }
  scope :potential_customers, -> { where(:active => false).not_archived }
  scope :archived_customers, -> { where(:archived => true) }

Controller

 @current_customers = Customer.current_customers.includes(:contacts,:contracts)

View

link_to "Current Clients #{@count_current.size}"

Answer 1

You may find help here

As @Gabbar pointed out and I will add to it, your app right now is eager-loading (opposite of lazy-loading ) which means that you are loading more from the database than needed. What we need to do is optimize but that totally depends on your use-case.

Whatever the use-case, you can do a few common things to make things better: You can implement pagination (there are gems for it and you can do it yourself too) or infinite scrolling. In this case, you will be loading a set amount of records from db at first but as soon as user wants more, either they will scroll down or click 'next' button and your action will be called again but with an increment in the page number which means get the next set of records.

Implementing based on scroll involves JS and the view-height etc. but pagination is much simpler.

Gems:

kaminari gem

infinite-pages

Using includes

One more thing you must do is, use include in query if your records are related. Using include is tricky but very very helpful in time-saving. It will fetch the related needed record together in one go from database unlike your code going to and fro database multiple times. Fetching from database takes a lot of time as compared to fetching from RAM.

@users = User.all.includes(:comments) #comments for all users brought along with users but saved in RAM for future access.
@comments = @users.map(&:comments) # no need to go to db again, just RAM.

Using scopes in models:

Creating scopes in models helps too. In your case, you should create scopes like this:

  scope :archived_customers, -> { where('archived IS false') }
  scope :potential_customers, -> { where('active IS false') }

  **OR**

  scope :archived_customers, -> { where(:archived => false) }
  scope :potential_customers, -> { where(:active => false) }

Answer 2

Loading all the available records in a single query can be very costly. Moreover, a user may be interested only in a couple of the most recent records (ie, the latest posts in a blog) and does not want to wait for all records to load and render.

There are couples of ways to sort out this problem

example#1 implementation of Load More

example#2 implementation of Infinite Scrolling

example#3 implementation of pagination