From 6c7115a9c9922a4abc9e65e7834c4a78d4dc2577 Mon Sep 17 00:00:00 2001
From: Travis Grathwell <tjgrathwell@gmail.com>
Date: Tue, 10 Feb 2015 20:59:25 -0800
Subject: [PATCH] Cache event role on users to reduce RSVP querying on homepage

The homepage does a bunch of queries for each event to figure
out which buttons to show the logged-in user based on whether
they're an organizer, volunteer, etc.

There is now a User#event_attendances method which gathers
all of a user RSVPs into a hash like:
5 => {
  role: Role::STUDENT,
  waitlist_position: 2
}

This structure is memoized on the user so if we need to ask
event.organizer?(user) and event.volunteer?(user) etc multiple
times in the single request it just looks up the result in
yonder hash.
---
 app/models/event.rb | 10 +++++-----
 app/models/user.rb  | 13 +++++++++++++
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/app/models/event.rb b/app/models/event.rb
index 192d72a07..f0cdf72fc 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -208,23 +208,23 @@ def rsvp_for_user(user)
   end
 
   def no_rsvp?(user)
-    !rsvps.where(user_id: user.id).any?
+    user.event_role(self).blank?
   end
 
   def student?(user)
-    student_rsvps.where(user_id: user.id).any?
+    user.event_role(self) == Role::STUDENT
   end
 
   def waitlisted_student?(user)
-    student_waitlist_rsvps.where(user_id: user.id).any?
+    student?(user) && user.event_attendances[id][:waitlist_position].present?
   end
 
   def volunteer?(user)
-    volunteer_rsvps.where(user_id: user.id).any?
+    user.event_role(self) == Role::VOLUNTEER
   end
 
   def organizer?(user)
-    organizer_rsvps.where(user_id: user.id).any?
+    user.event_role(self) == Role::ORGANIZER
   end
 
   def checkiner?(user)
diff --git a/app/models/user.rb b/app/models/user.rb
index df7203c15..688b42ad8 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -59,6 +59,19 @@ def meetup_id
     authentications.find { |a| a.provider == 'meetup' }.try(:uid)
   end
 
+  def event_attendances
+    @event_attendances ||= rsvps.each_with_object({}) do |rsvp, hsh|
+      hsh[rsvp.event_id] = {
+        role: rsvp.role,
+        waitlist_position: rsvp.waitlist_position
+      }
+    end
+  end
+
+  def event_role(event)
+    event_attendances.fetch(event.id, {})[:role]
+  end
+
   private
 
   def make_empty_profile