From f959e632eaeddfc450401509f5c3028e9b6ca2f3 Mon Sep 17 00:00:00 2001
From: Matt-Yorkley <9029026+Matt-Yorkley@users.noreply.github.com>
Date: Tue, 7 Apr 2020 15:15:25 +0200
Subject: [PATCH] Modify Spree::Stock::Quantifier to not re-fetch stock items
 if they are already eager-loaded

This helps to remove a big N+1 here, and will also be very helpful elsewhere in the app
---
 app/models/spree/stock/quantifier.rb | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/app/models/spree/stock/quantifier.rb b/app/models/spree/stock/quantifier.rb
index 6b1c11de62..806fdf33dd 100644
--- a/app/models/spree/stock/quantifier.rb
+++ b/app/models/spree/stock/quantifier.rb
@@ -5,7 +5,7 @@ module Spree
 
       def initialize(variant)
         @variant = variant
-        @stock_items = Spree::StockItem.joins(:stock_location).where(:variant_id => @variant, Spree::StockLocation.table_name =>{ :active => true})
+        @stock_items = fetch_stock_items
       end
 
       def total_on_hand
@@ -23,6 +23,16 @@ module Spree
       def can_supply?(required)
         total_on_hand >= required || backorderable?
       end
+
+      private
+
+      def fetch_stock_items
+        # Don't re-fetch associated stock items from the DB if we've already eager-loaded them
+        return @variant.stock_items.to_a if @variant.stock_items.loaded?
+
+        Spree::StockItem.joins(:stock_location).
+          where(:variant_id => @variant, Spree::StockLocation.table_name => { active: true })
+      end
     end
   end
 end