rework some mysql-specific stuff, closes #4090

Change-Id: I6791f124aae5caf2c5a3d5cd2b36dce60657d7ca
Reviewed-on: https://gerrit.instructure.com/2843
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Zach Wily <zach@instructure.com>
Reviewed-by: Brian Palmer <brianp@instructure.com>

app/controllers/courses_controller.rb

@@ -160,12 +160,10 @@ class CoursesController < ApplicationController
       @range_end = Date.tomorrow
       
       query = "SELECT COUNT(id), SUM(size) FROM attachments WHERE context_id=%s AND context_type='Course' AND root_attachment_id IS NULL AND file_state != 'deleted'"
-      res = ActiveRecord::Base.connection.execute(query % [@context.id])
-      row = res.fetch_row
+      row = ActiveRecord::Base.connection.select_rows(query % [@context.id]).first
       @file_count, @files_size = [row[0].to_i, row[1].to_i]
       query = "SELECT COUNT(id), SUM(max_size) FROM media_objects WHERE context_id=%s AND context_type='Course' AND attachment_id IS NULL AND workflow_state != 'deleted'"
-      res = ActiveRecord::Base.connection.execute(query % [@context.id])
-      row = res.fetch_row
+      row = ActiveRecord::Base.connection.select_rows(query % [@context.id]).first
       @media_file_count, @media_files_size = [row[0].to_i, row[1].to_i]
       
       if params[:range] && params[:date]

lib/reporting/counts_report.rb

@@ -222,8 +222,7 @@ class CountsReport
 
   def last_activity(account_id)
     query = "SELECT max(created_at) FROM #{PageView.table_name} WHERE account_id = #{account_id}"
-    res = ActiveRecord::Base.connection.execute(query)
-    res.fetch_row[0] rescue nil
+    ActiveRecord::Base.connection.select_value(query)
   end
 
   def get_course_ids(account, course_ids)
@@ -237,14 +236,11 @@ class CountsReport
   end
 
   def get_count_from_query(query)
-    res = ActiveRecord::Base.connection.execute(query)
-    res.fetch_row[0].to_i
+    ActiveRecord::Base.connection.select_value(query).to_i
   end
   
   def get_count_and_size_from_query(query)
-    res = ActiveRecord::Base.connection.execute(query)
-    row = res.fetch_row
-    [row[0].to_i, row[1].to_i]
+    ActiveRecord::Base.connection.select_rows(query).first.map(&:to_i)
   end
 
   def should_use_default_account_course(course)