Perf: Cache inventory calculation in DashboardController

Author: coalest

app/controllers/dashboard_controller.rb

@@ -3,7 +3,8 @@ class DashboardController < ApplicationController
   respond_to :html, :js
 
   def index
-    @org_stats = OrganizationStats.new(current_organization)
+    inventory = View::Inventory.new(current_organization.id)
+    @org_stats = OrganizationStats.new(current_organization, inventory)
     @partners_awaiting_review = current_organization.partners.awaiting_review
     @outstanding_requests = current_organization
       .ordered_requests
@@ -12,7 +13,7 @@ def index
       .order(:created_at)
       .limit(25)
 
-    @low_inventory_report = LowInventoryQuery.call(current_organization)
+    @low_inventory_report = LowInventoryQuery.call(current_organization, inventory)
 
     # passing nil here filters the announcements that didn't come from an organization
     @broadcast_announcements = BroadcastAnnouncement.filter_announcements(nil)

app/models/organization_stats.rb

@@ -7,8 +7,9 @@ class OrganizationStats
            :donation_sites,
            to: :current_organization, allow_nil: true
 
-  def initialize(organization)
+  def initialize(organization, inventory)
     @current_organization = organization
+    @inventory = inventory
   end
 
   def partners_added
@@ -26,11 +27,10 @@ def donation_sites_added
   def locations_with_inventory
     return [] unless storage_locations
 
-    inventory = View::Inventory.new(current_organization.id)
     storage_locations.select { |loc| inventory.quantity_for(storage_location: loc.id).positive? }
   end
 
   private
 
-  attr_reader :current_organization
+  attr_reader :current_organization, :inventory
 end

app/queries/low_inventory_query.rb

@@ -1,8 +1,7 @@
 class LowInventoryQuery
   LowInventoryItem = Data.define(:id, :name, :on_hand_minimum_quantity, :on_hand_recommended_quantity, :total_quantity)
 
-  def self.call(organization)
-    inventory = View::Inventory.new(organization.id)
+  def self.call(organization, inventory)
     items = inventory.all_items.uniq(&:item_id)
 
     low_inventory_items = []