title: Rails - Active Record: add extra select column to find(:all)
body: <p>I want to add new column <code>sum(time_entries.hours)</code> to sql select 
  I'm querying entries like this:
  </p>
  
  <pre><code>issues = Issue.visible.where(options[:conditions]).all(
      :include =&gt; ([:status, :project, :time_entries] + (options[:include] || [])).uniq,
      :conditions =&gt; statement,
      :order =&gt; order_option,
      :joins =&gt; query_joins(order_option.join(',')),
      :limit =&gt; options[:limit],
      :offset =&gt; options[:offset],
      :group =&gt; "#{Issue.table_name}.id"
  )
  </code></pre>
  
  <p>It generates this select:
  </p>
  
  <pre><code>SELECT
   "issues"."id"                         AS t0_r0,
   ...
   "time_entries"."hours"                AS t3_r4,
   ...
   "versions"."sharing"                  AS t8_r9
  FROM "issues"
   LEFT OUTER JOIN "projects" ON "projects"."id" = "issues"."project_id"
   LEFT OUTER JOIN "issue_statuses" ON "issue_statuses"."id" = "issues"."status_id"
   LEFT OUTER JOIN "time_entries" ON "time_entries"."issue_id" = "issues"."id"
   LEFT OUTER JOIN "users" ON "users"."id" = "issues"."assigned_to_id"
   LEFT OUTER JOIN "trackers" ON "trackers"."id" = "issues"."tracker_id"
   LEFT OUTER JOIN "enumerations"
     ON "enumerations"."id" = "issues"."priority_id" AND "enumerations"."type" IN ('IssuePriority')
   LEFT OUTER JOIN "issue_categories" ON "issue_categories"."id" = "issues"."category_id"
   LEFT OUTER JOIN "versions" ON "versions"."id" = "issues"."fixed_version_id"
  WHERE "issues"."id" IN (1) AND (projects.status &lt;&gt; 9 AND projects.id IN (SELECT
                                                                         em.project_id
                                                                       FROM enabled_modules em
                                                                       WHERE em.name =     'issue_tracking')) AND
    ((issues.status_id IN (SELECT
                             id
                           FROM issue_statuses
                           WHERE is_closed = 'f')))
  GROUP BY issues.id
  ORDER BY issues.id
   DESC
  </code></pre>
  
  <p>I tried insert <code>:select=&gt;"*, sum(time_entries.hours)"</code> into hash parameter to <code>all</code> method, but there is no effect.</p>
  
  <p>How can I add new column to this select? 
  Also I need preserve all current columns, since they are used in filters.
  Is there any way without specifying all columns by hands?</p>
  
  <p><strong>UPDATE:</strong>
  Ruby 1.9.3
  Rails 3.2.13</p>