Rails - Active Record：添加额外的选择列来查找（：全部）

我想添加新列sum(time_entries.hours)到sql选择 我正在查询这样的条目：

issues = Issue.visible.where(options[:conditions]).all(
    :include => ([:status, :project, :time_entries] + (options[:include] || [])).uniq,
    :conditions => statement,
    :order => order_option,
    :joins => query_joins(order_option.join(',')),
    :limit => options[:limit],
    :offset => options[:offset],
    :group => "#{Issue.table_name}.id"
)

它生成此选择：

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 <> 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

我尝试插入:select=>"*, sum(time_entries.hours)"到哈希参数all方法，但是没有效果。

如何向此选择添加新列？ 另外，我需要保留所有当前列，因为它们在过滤器中使用。 有没有办法不用手动指定所有列？

UPDATE:红宝石 1.9.3 轨道 3.2.13

表名看起来像来自Redmine。我最近实际上遇到了类似的问题。我发现所选列源于可见范围。我无法确切地确定为什么，但如果没有它，“选择”选项就会按预期工作。

Using

Issue.select("#{Issue.table_name}.*, sum(#{TimeEntries.table_name}.hours AS total_hours").where("#{your_conditions}").group(:id).all

应该给你你想要的数据。附加列可以作为问题属性直接访问：

Issue.total_hours

Edit:

如果无法同时选择所有问题字段（用于创建完整的问题对象）和总和，则在获取所需问题后需要使用第二条语句。

issues = Issue.visible.where("#{issue_conditions}").all
issue_ids = issues.map(&:id)
# if you do not need the issue objects, use .pluck(:id) instead of .all

spent_hours = TimeEntries.select('issue_id, sum(hours)')
                         .where(:issue_id => issue_ids)
                         .where("#{other_time_conditions}")
                         .group(:issue_id).all

或者，您可以使用 Redmines Issue 类中包含的便利函数。使用它可以让软件为您完成工作：

i = Issue.includes(:time_entries).find(1)
i.total_spent_hours

包含可确保计算不会再次访问数据库，因为所有相关关联都已加载。