Optimize Project#ci_service(s)

The method Project#ci_services would load all services into memory (including _all_ their columns) and then use Enumerable#select to reduce the list. Project#ci_service in turn would further reduce this list down to just 1 Service instance. Instead of doing all this in Ruby we can just offload the work to the database, reducing the amount of time spent in these methods. These changes reduce the time of the first call to Project#ci_services from around 240 ms to around 10 ms, though the final timings will vary based on database load. Because Project#ci_service is memoized there's no further overhead introduced by using a database query. Fixes gitlab-org/gitlab-ce#14186

Optimize Project#ci_service(s)
f2992cf3 · Yorick Peterse · 491ac7ce · f2992cf3
Commit f2992cf3 authored Mar 10, 2016 by Yorick Peterse
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project.rb app/models/project.rb +2 -2

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--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -528,11 +528,11 @@ class Project < ActiveRecord::Base
  end

  def ci_services
-    services.select { |service| service.category == :ci }
+    services.where(category: :ci)
  end

  def ci_service
-    @ci_service ||= ci_services.find(&:activated?)
+    @ci_service ||= ci_services.reorder(nil).find_by(active: true)
  end

  def jira_tracker?