MongoDB 使用group by 并显示其他列max值

以下脚本实现功能为把word_info表通过word字段去重，并写到到word_info_new表里

db.word_info.aggregate([{$group:        { _id:"$word" ,         meaning:{$max:"$meaning"},          usphonetic:{$max:"$usphonetic"}         } }]).forEach(            function(dc){                    db.word_info_new.insert(                                    {"word":dc._id,                                        "meaning":dc.meaning,                                        "usphonetic":dc.usphonetic                                    }                                )}    );