活动记录性能问题

Question

I have a rails application and I'm currently running into performance issues at scale. I am using Rails 4 and MySQL for my backend.

I have a model named Coaches and I would like to group my response so that it only sends coaches with distinct emails.

Here is an example:

Coach.group(:email)

However when i use this code with my production workload, it takes far too long to for Active Record to produce the result, see below.

Coach Load (193743.7ms)  SELECT `coaches`.* FROM `coaches` WHERE `coaches`.`deleted_at` IS NULL GROUP BY `coaches`.`email`

I have an index on the email and deleted_at column in my coaches table.

Has anyone run into similar issues in the past?

Answer 1

您还需要在deleted_at列上应用indexing ，并且一种合适的解决方案是使用分页（例如以限制格式使用数据）在这种情况下将为您提供帮助。