From c85d00fcb8f88fcd5fadf652e854fe9a08740124 Mon Sep 17 00:00:00 2001
From: Pau Perez <saulopefa@gmail.com>
Date: Mon, 29 Jul 2019 19:52:50 +0200
Subject: [PATCH] Remove N+1 while fetching distributors of OCs

What used to be done as

```sql
SELECT "order_cycles".* FROM "order_cycles"
WHERE (order_cycles.orders_open_at <= '2019-07-29 17:45:20.137294'
  AND order_cycles.orders_close_at >= '2019-07-29 17:45:20.137333')

SELECT DISTINCT "enterprises".* FROM "enterprises"
INNER JOIN "exchanges" ON "enterprises"."id" = "exchanges"."receiver_id"
WHERE "exchanges"."order_cycle_id" = 1
  AND "exchanges"."incoming" = 'f'
(...)
SELECT DISTINCT "enterprises".* FROM "enterprises"
INNER JOIN "exchanges" ON "enterprises"."id" = "exchanges"."receiver_id"
WHERE "exchanges"."order_cycle_id" = 4
  AND "exchanges"."incoming" = 'f'
```

it became

```sql
SELECT "order_cycles".* FROM "order_cycles"
WHERE (order_cycles.orders_open_at <= '2019-07-29 17:45:20.137294'
  AND order_cycles.orders_close_at >= '2019-07-29 17:45:20.137333')

SELECT "exchanges".* FROM "exchanges"
WHERE "exchanges"."incoming" = 'f'
  AND "exchanges"."order_cycle_id" IN (1, 2, 3, 4)

SELECT "enterprises".* FROM "enterprises"
WHERE "enterprises"."id" IN (3, 4, 5, 6)
```

I haven't got any perf numbers yet but each of the N+1 queries took as
long as the single `enterprises` query on my dev machine.

This should have a noticeable perf impact since the changed method
belongs to the `BaseController` seems to be executed in all HTML
requests as it gets called by

```ruby
before_filter :warn_invalid_order_cycles, if: :html_request?
```
---
 app/controllers/spree/admin/base_controller_decorator.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/controllers/spree/admin/base_controller_decorator.rb b/app/controllers/spree/admin/base_controller_decorator.rb
index 941b679c59..7e5293024d 100644
--- a/app/controllers/spree/admin/base_controller_decorator.rb
+++ b/app/controllers/spree/admin/base_controller_decorator.rb
@@ -61,7 +61,7 @@ Spree::Admin::BaseController.class_eval do
 
   def active_distributors_not_ready_for_checkout
     ocs = OrderCycle.managed_by(spree_current_user).active
-    distributors = ocs.map(&:distributors).flatten.uniq
+    distributors = ocs.includes(:distributors).map(&:distributors).flatten.uniq
     Enterprise.where('enterprises.id IN (?)', distributors).not_ready_for_checkout
   end