Question

In my view, I’ve got a fiddly loop which creates 500 SQL queries (to get the info for 500 books). How can I avoid lots of SQL queries by loading a variable up in the controller?

My current (pseudo) code:

controller index action:

@books = Book.scoped.where(:client_id => @client.id).text_search(params[:query])
@feature_root = Book.multiple_summary_details_by_category( @books ) 
  #...returns a hash of books
@features = @feature_root.to_a.paginate(:page => params[:page], :per_page => 4)

index.html.haml

    = render :partial => "feature", :locals => { :features => @features }

_features.html.haml

  - features.each_with_index do |(cat_name, array_of_books), i|  
    %h2
      = cat_name
    - array_of_books[0..10].each do |feature|
      = link_to image_tag(feature[:cover], :class => "product_image_tiny"), book_path(feature[:book])
    # more code
    - array_of_books.sort_by{ |k, v| k["Author"] }.each do |feature|
      - feature.each do |heading,value|
        %span.summary_title
          = heading + ':'
        %span.summary_value
          = value

Answer 1

What have you tried so far? It should be quite easy with standard ActiveRecord queries as documented in http://guides.rubyonrails.org/active_record_querying.html.

Also, instead of

array_of_books.sort_by{ |k, v| k["Author"] }

try something like

Book.order("author DESC")

(not sure about your exact model here) to let the db do the sorting rather than putting them in an array and let ruby handle it.