:counter_cache => true for storing sum
I have the table users and scores. Here are the associations:
belongs_to :user #score model has_many :scores #user model
The table users has the column called scores_count. In this column I store the sum of all values in the table scores.
I wanted to use this way for storing the sum of all scores in the column scores_count: :counter_cache => true
But :counter_cache => true saving only the count of rows in the table scores. Is there any similar method for storing the sum of all values from the table scores? Or this task I have to implement by myself?
No. You'll have to implement it yourself. Counter-cache is for storing the number of associated records only. You could implement it using a callback on Score to update the associated User. See also How can I cache a calculated column in rails?
Further, unless you have noticeable performance issues with summing each time, avoid using a cache like this. It's just something that can easily go wrong and get out-of-date. It's not worth the trouble if you don't really need it.
You could use counter_culture gem.
class Score < ActiveRecord::Base belongs_to :user counter_culture :user, column_name: 'scores_sum', delta_column: 'score_value' end