Perf: Refactor ProductDrive#index with service

Author: coalest

app/controllers/product_drives_controller.rb

@@ -6,7 +6,6 @@ def index
     setup_date_range_picker
     @product_drives = current_organization
                      .product_drives
-                     .includes(donations: {line_items: :item})
                      .class_filter(filter_params)
                      .within_date_range(@selected_date_range)
                      .order(start_date: :desc)
@@ -15,6 +14,11 @@ def index
     @item_categories = current_organization.item_categories
     @selected_name_filter = filter_params[:by_name]
     @selected_item_category = filter_params[:by_item_category_id]
+    @summary = ProductDriveSummaryService.new(
+      product_drives: @product_drives,
+      within_date_range: @selected_date_range,
+      item_category_id: @selected_item_category
+    ).call
 
     respond_to do |format|
       format.html

app/models/product_drive.rb

@@ -19,7 +19,7 @@ class ProductDrive < ApplicationRecord
 
   scope :by_name, ->(name_filter) { where(name: name_filter) }
   scope :by_item_category_id, ->(item_category_id) {
-    joins(donations: {line_items: :item})
+    includes(donations: {line_items: :item})
       .where(item: { item_category_id: item_category_id })
   }
 

app/services/product_drive_summary_service.rb

@@ -0,0 +1,52 @@
+class ProductDriveSummaryService
+  def initialize(product_drives:, within_date_range:, item_category_id:)
+    @product_drives = product_drives
+    @within_date_range = within_date_range
+    @item_category_id = item_category_id
+  end
+
+  def call
+    calculate_summary
+    self
+  end
+
+  def fetch_quantity(product_drive_id)
+    @summary.dig(product_drive_id, :quantity)
+  end
+
+  def fetch_unique_item_count(product_drive_id)
+    @summary.dig(product_drive_id, :unique_item_count)
+  end
+
+  def fetch_value(product_drive_id)
+    @summary.dig(product_drive_id, :value)
+  end
+
+  private
+
+  # Returns hash of total quantity, unique item count and value per product drive
+  # Example return: { 1 => { quantity: 15, unique_item_count: 2, value: 100 }, ...}
+  #
+  # @return [Hash<Hash<Symbol, Integer>>]
+  def calculate_summary
+    @summary ||= begin
+      query = ProductDrive
+        .left_joins(donations: {line_items: [:item]})
+        .where(id: @product_drives.ids)
+        .within_date_range(@within_date_range)
+        .group("product_drives.id")
+        .distinct
+
+      query = query.where(items: {item_category_id: @item_category_id}) if @item_category_id.present?
+
+      query.pluck(Arel.sql(
+        "product_drives.id AS id,
+        COALESCE(SUM(line_items.quantity), 0) AS quantity,
+        COUNT(DISTINCT line_items.item_id) AS unique_item_count,
+        COALESCE(SUM(COALESCE(items.value_in_cents, 0) * line_items.quantity), 0) AS value"
+      )).to_h do |(id, quantity, unique_item_count, value)|
+        [id, {quantity:, unique_item_count:, value:}]
+      end
+    end
+  end
+end

app/views/product_drives/index.html.erb

@@ -104,9 +104,9 @@
                   <td><%= product_drive.start_date.strftime("%m-%d-%Y") %></td>
                   <td><%= product_drive.end_date&.strftime("%m-%d-%Y") %></td>
                   <td><%= is_virtual(product_drive: product_drive) %></td>
-                  <td class="text-right"><%= product_drive.donation_quantity_by_date(selected_range, @selected_item_category) %></td>
-                  <td class="text-right"><%= product_drive.distinct_items_count_by_date(selected_range, @selected_item_category) %></td>
-                  <td class="text-right"><strong><%= dollar_value(product_drive.in_kind_value) %></strong></td>
+                  <td class="text-right"><%= @summary.fetch_quantity(product_drive.id) %></td>
+                  <td class="text-right"><%= @summary.fetch_unique_item_count(product_drive.id) %></td>
+                  <td class="text-right"><strong><%= dollar_value(@summary.fetch_value(product_drive.id)) %></strong></td>
                   <td class="text-right"><%= view_button_to product_drive_path(product_drive.id) %></td>
                 </tr>
               <% end %>