Avoid two unnecessary queries just to check if an instrument is offline

The method #offline? needs to check whether there are any current offline reservations. By refactoring to an association and using #present?, Rails will memoize the association and check without another DB query.
wyeworks · Mar 14, 2019 · 633bb82 · 633bb82
1 parent 4ce1c74
commit 633bb82
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Showing 3 changed files with 8 additions and 8 deletions.
diff --git a/app/models/concerns/products/scheduling_support.rb b/app/models/concerns/products/scheduling_support.rb
@@ -59,7 +59,7 @@ def next_available_reservation(after: Time.zone.now, duration: 1.minute, options
   end
 
   def offline?
-    offline_reservations.current.any?
+    current_offline_reservations.present?
   end
 
   def offline_category

diff --git a/app/models/instrument.rb b/app/models/instrument.rb
@@ -9,12 +9,12 @@ class Instrument < Product
 
   RESERVE_INTERVALS = [1, 5, 10, 15, 30, 60].freeze
 
-  # Associations
-  # -------
-
-  has_many :instrument_price_policies, foreign_key: "product_id"
-  has_many :admin_reservations, foreign_key: "product_id"
-  has_many :offline_reservations, foreign_key: "product_id"
+  with_options foreign_key: "product_id" do |instrument|
+    instrument.has_many :admin_reservations
+    instrument.has_many :instrument_price_policies
+    instrument.has_many :offline_reservations
+    instrument.has_many :current_offline_reservations, -> { current }, class_name: "OfflineReservation"
+  end
   has_one :alert, dependent: :destroy, class_name: "InstrumentAlert"
 
   email_list_attribute :cancellation_email_recipients

diff --git a/spec/models/instrument_spec.rb b/spec/models/instrument_spec.rb
@@ -796,7 +796,7 @@
 
       it "switches the instrument to be online" do
         expect { instrument.online! }
-          .to change { instrument.online? }
+          .to change { instrument.reload.online? }
           .from(false).to(true)
           .and change { offline_reservation.reload.reserve_end_at }.from(nil)
       end