From ead1ab31b4e1af10df30dbcc97c9be59dbbd9f26 Mon Sep 17 00:00:00 2001
From: Pau Perez <saulopefa@gmail.com>
Date: Thu, 25 Mar 2021 09:40:08 +0100
Subject: [PATCH] Fix multiple N+1 on /admin/customers.json

This (should) considerably improve traces like
https://app.datadoghq.com/apm/trace/917632173599137280?spanID=3163385094622710144&env=production&sort=time&colorBy=service&spanViewType=metadata&graphType=flamegraph&shouldShowLegend=true
by fixing the following 3 N+1s

```
user: root
GET /admin/customers.json?enterprise_id=4
USE eager loading detected
  Customer => [:enterprise]
  Add to your query: .includes([:enterprise])
Call stack
  /usr/src/app/app/serializers/api/admin/customer_with_calculated_balance_serializer.rb:24:in `balance_value'
  /usr/src/app/app/serializers/api/admin/customer_with_calculated_balance_serializer.rb:9:in `balance'
  /usr/src/app/app/controllers/admin/customers_controller.rb:20:in `block (2 levels) in index'
  /usr/src/app/app/controllers/admin/customers_controller.rb:17:in `index'

user: root
GET /admin/customers.json?enterprise_id=4
USE eager loading detected
  Spree::Address => [:state]
  Add to your query: .includes([:state])
Call stack
  /usr/src/app/app/serializers/api/address_serializer.rb:14:in `state_name'
  /usr/src/app/app/controllers/admin/customers_controller.rb:20:in `block (2 levels) in index'
  /usr/src/app/app/controllers/admin/customers_controller.rb:17:in `index'

user: root
GET /admin/customers.json?enterprise_id=4
USE eager loading detected
  Spree::Address => [:country]
  Add to your query: .includes([:country])
Call stack
  /usr/src/app/app/serializers/api/address_serializer.rb:10:in `country_name'
  /usr/src/app/app/controllers/admin/customers_controller.rb:20:in `block (2 levels) in index'
  /usr/src/app/app/controllers/admin/customers_controller.rb:17:in `index'
```

This popped up after improving the balances calculation. Now, that it's
fast, it's clear that are more performance problems on that endpoint.
We'll see if there are any left after this.
---
 app/controllers/admin/customers_controller.rb | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/app/controllers/admin/customers_controller.rb b/app/controllers/admin/customers_controller.rb
index 4a2f4242e9..9057735bcb 100644
--- a/app/controllers/admin/customers_controller.rb
+++ b/app/controllers/admin/customers_controller.rb
@@ -74,7 +74,12 @@ module Admin
     def collection
       if json_request? && params[:enterprise_id].present?
         customers_relation.
-          includes(:bill_address, :ship_address, user: :credit_cards)
+          includes(
+            :enterprise,
+            { bill_address: [:state, :country] },
+            { ship_address: [:state, :country] },
+            user: :credit_cards
+          )
       else
         Customer.where('1=0')
       end