Gateway timeout before How to optimize - sql

Question

I have what I assume is a pretty simple query, which is essentially collecting our Customer object and counting the orders associated with that customer. But every time I try to load more than a weeks worth of Customer data, I get 504 timeouts, I assume from the system taking to long to collect everything. We use Spree as our eComm framework, which handles the Product & Order.
What am I missing that's making this collection of objects so labor intensive on our servers? It's a good 45 seconds before our server kicks us off with the 504.
customer.rb (model):
has_many :orders, foreign_key: :customer_id, class_name: "Spree::Order"
def sorted_orders
orders.sort_by(&:completed_at)
end
def non_sub_orders
orders.where(purchased_via_subscription: false)
end
def standard_items
orders.joins(:products).merge(Spree::Product.where(is_default: true))
end
def spec_items
orders.joins(:products).merge(Spree::Product.where(is_default: false))
end
customers_controller.rb:
#customers = Customer.joins(:orders).where(spree_orders: {purchased_via_subscription: false, completed_at: #from...#to}).uniq
customers/index.html.erb (view):
<form class="filter_form col-10">
Dates: <%= text_field(:date, :from, type: 'date', value: params[:date].try(:[], :from), style: "") %>
to <%= text_field(:date, :to, type: 'date', value: params[:date].try(:[], :to), style: "") %>
<input type="submit" value="Filter" />
</form>
<% #customers.each_with_index do |c, index| %>
<tbody id="tbodyid">
<tr>
<td><%= index + 1 %></td>
<td><%= c.email %></td>
<td><%= c.sorted_orders.first.completed_at.strftime("%D") %></td>
<td><%= c.sorted_orders.last.completed_at.strftime("%D") %></td>
<td><%= c.spec_items.count %></td>
<td><%= c.standard_items.count %></td>
<td><%= c.non_sub_orders.count %></td>
<td><%= number_to_currency(c.total_revenue/c.non_sub_orders.count) %></td>
<td><%= number_to_currency(c.total_revenue) %></td>
</tr>
</tbody>
<% end %>

Answer 1

this is not only N + 1 queries problem but also custom queries (which #includes will not fix).
solution (maybe): create custom associations for custom queries and preload them.
# customer.rb
has_many :orders, foreign_key: :customer_id, class_name: "Spree::Order"
has_many :sorted_orders, -> { sort_by(&:completed_at) }, class_name: "Spree::Order"
has_many :non_sub_orders, -> { where(purchased_via_subscription: false) }, class_name: "Spree::Order"
has_many :standard_items, -> { joins(:products).merge(Spree::Product.where(is_default: true)) }, class_name: "Spree::Order"
has_many :spec_items, -> { joins(:products).merge(Spree::Product.where(is_default: false)) }, class_name: "Spree::Order"
# customers_controller.rb
#customers = Customer.joins(:orders)
.where(spree_orders: {purchased_via_subscription: false, completed_at: #from...#to})
.includes(:sorted_orders, :non_sub_orders, :standard_items, :spec_items)
.uniq