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counter_cache_usage

📊 Leverage counter_cache​

Counting associated records repeatedly is inefficient. Use Rails’ counter_cache to maintain a count column on the parent model, avoiding COUNT(*) queries.

# Migration to add comments_count to posts
add_column :posts, :comments_count, :integer, default: 0, null: false

# Comment model
class Comment < ApplicationRecord
  belongs_to :post, counter_cache: true
end

# Now you can display post.comments_count directly
<%= @post.comments_count %> comments