删除“重复对象”

假设我有一个来自同一个类的对象数组，这里有两个值得关注的属性：name和created_at。

如何在数组中找到具有相同名称的对象（被视为重复），然后删除数据库中的重复记录。 但是，具有最新created_at日期的对象是必须删除的对象。

Answer 1

seen = [] #sort by created date and iterate collection.sort({|a,b| a.created_at <=> b.created_at}).each do |obj| if seen.map(&:name).include? obj.name #check if the name has been seen already obj.destroy! else seen << obj #if not, add it to the seen array end end 

应该做好希望的工作。

Answer 2

如果在表上引入UNIQUE INDEX之前这只是一次性错误修正，那么您可以在SQL中执行此操作：

 DELETE FROM t WHERE id IN ( SELECT t1.id FROM t t1 LEFT JOIN t t2 ON t1.name = t2.name AND t2.created_at < t1.created_at WHERE t2.id IS NOT NULL )