From b139087c5fbaffbf54ae5b4b43bef07d262687b6 Mon Sep 17 00:00:00 2001
From: Matt-Yorkley <9029026+Matt-Yorkley@users.noreply.github.com>
Date: Thu, 11 May 2023 20:28:28 +0100
Subject: [PATCH 1/2] Clone ExchangeVariant objects in bulk

An ExchangeVariant is a simple representation of a join table between Exchange and Variant. Previously this code was triggering an additional INSERT query for every variant added to the newly cloned exchange. Some exchanges have ~3000 variants! The code now creates them in bulk in a single INSERT statement. When cloning large order cycles this can improve performance by ~1000% or so.
---
 app/models/exchange.rb | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/app/models/exchange.rb b/app/models/exchange.rb
index a315ccd1c6..2522d5622d 100644
--- a/app/models/exchange.rb
+++ b/app/models/exchange.rb
@@ -86,9 +86,9 @@ class Exchange < ApplicationRecord
     exchange = dup
     exchange.order_cycle = new_order_cycle
     exchange.enterprise_fee_ids = enterprise_fee_ids
-    exchange.variant_ids = variant_ids
     exchange.tag_ids = tag_ids
     exchange.save!
+    clone_all_exchange_variants(exchange.id)
     exchange
   end
 
@@ -105,4 +105,14 @@ class Exchange < ApplicationRecord
 
     receiver.touch_later
   end
+
+  private
+
+  def clone_all_exchange_variants(exchange_id)
+    return unless variant_ids.any?
+
+    ExchangeVariant.insert_all(
+      variant_ids.map{ |variant_id| { variant_id: variant_id, exchange_id: exchange_id } }
+    )
+  end
 end

From 636b365304966bd5ff64b4cdcc08753fb765415f Mon Sep 17 00:00:00 2001
From: Maikel Linke <maikel@email.org.au>
Date: Fri, 12 May 2023 10:30:47 +1000
Subject: [PATCH 2/2] Tell Rubocop and devs about bulk insert

---
 app/models/exchange.rb | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/app/models/exchange.rb b/app/models/exchange.rb
index 2522d5622d..e52d412c96 100644
--- a/app/models/exchange.rb
+++ b/app/models/exchange.rb
@@ -108,10 +108,13 @@ class Exchange < ApplicationRecord
 
   private
 
+  # An Order Cycle can have thousands of ExchangeVariants.
+  # It's a simple association without any callbacks on creation. So we can
+  # insert in bulk and improve the performance tenfold for large order cycles.
   def clone_all_exchange_variants(exchange_id)
     return unless variant_ids.any?
 
-    ExchangeVariant.insert_all(
+    ExchangeVariant.insert_all( # rubocop:disable Rails/SkipsModelValidations
       variant_ids.map{ |variant_id| { variant_id: variant_id, exchange_id: exchange_id } }
     )
   end