Merge branch 'query-counting-should-not-include-cached-queries' into 'master'

Do not count rails sql cache as queries in query limiting

See merge request gitlab-org/gitlab-ce!17253

lib/gitlab/query_limiting/active_support_subscriber.rb

@@ -3,9 +3,11 @@ module Gitlab
     class ActiveSupportSubscriber < ActiveSupport::Subscriber
       attach_to :active_record
 
-      def sql(*)
+      def sql(event)
+        unless event.payload[:name] == 'CACHE'
           Transaction.current&.increment
         end
       end
     end
+  end
 end

spec/lib/gitlab/query_limiting/active_support_subscriber_spec.rb

 require 'spec_helper'
 
 describe Gitlab::QueryLimiting::ActiveSupportSubscriber do
-  describe '#sql' do
-    it 'increments the number of executed SQL queries' do
-      transaction = double(:transaction)
+  let(:transaction) { instance_double(Gitlab::QueryLimiting::Transaction, increment: true) }
 
+  before do
     allow(Gitlab::QueryLimiting::Transaction)
       .to receive(:current)
       .and_return(transaction)
+  end
+
+  describe '#sql' do
+    it 'increments the number of executed SQL queries' do
+      User.count
 
       expect(transaction)
-        .to receive(:increment)
-        .at_least(:once)
+        .to have_received(:increment)
+        .once
+    end
 
+    context 'when the query is actually a rails cache hit' do
+      it 'does not increment the number of executed SQL queries' do
+        ActiveRecord::Base.connection.cache do
+          User.count
           User.count
         end
+
+        expect(transaction)
+          .to have_received(:increment)
+          .once
+      end
+    end
   end
 end