I thought reset_counter method is to reset a counter_cache column to be 0, but it is not. After trying several times, I finally realize that reset_counter is to update the value of counter_cache column to the exact count of associations. The usecase of reset_counter is when you add the counter_cache in migration and update the counter_cache value, like
def self.up
add_column :posts, :comments_count
Post.all.each do |post|
Post.reset_counter(post.id, :comments)
end
end
it will add comments_count column to posts table, and calculate the comments count for each post, and set it to posts' comments_count column.
I didn't find a method to reset the counter_cache column to be 0, why? Because counter_cache is used to cache the association count, it will be incremented and decremeneted automatically, you should never reset it 0. If you find you need to reset counter_cache to 0, that means it's a wrong usage of counter_cache.
