Minimizing number of Queries - ruby-on-rails

Question

I currently have this:
data = []
products.each do |product|
categories = product.shop_categories.select("shop_categories.id, shop_categories.name").map do |category|
{
:name => category.name,
:category_id => category.id.to_s
}
end
data << {
:name => product.name,
:product_id => product.productid,
:manufacturer => product.manufacturer,
:detail => product.description,
:categories => categories,
:sales_rank => product.sales_rank,
:sale_price => product.sale_price.to_f,
:price => product.price.to_f,
:images => product.images,
:url => product.url,
:is_rated => current_user.voted_for?(product),
:is_liked => current_user.voted_as_when_voted(product),
:is_in_wishlist => current_user.has_product_in_wishlist?(product)
}
end
This part where products are searched for its shop_categories are taking up a huge amount of time to query since every product (100 per run) when it searches for the products' shop_categories.
Is there a way to minimize the number of queries or at least minimize the CPU being used up by this process?

Answer 1

Use includes to eager-load the association:
data = Product.includes(:shop_categories).collect do |product|
{
:name => product.name,
:product_id => product.productid,
:manufacturer => product.manufacturer,
:detail => product.description,
:categories => product.categories.collect { |c| { :name => c.name, :category_id => c.id.to_s } },
:sales_rank => product.sales_rank,
:sale_price => product.sale_price.to_f,
:price => product.price.to_f,
:images => product.images,
:url => product.url,
:is_rated => current_user.voted_for?(product),
:is_liked => current_user.voted_as_when_voted(product),
:is_in_wishlist => current_user.has_product_in_wishlist?(product)
}
end