我想在$bucket函数中单独处理$group的结果。我的数据:{"_id":1,"title":"ThePillarsofSociety","artist":"Grosz","year":1926,"type":1}{"_id":2,"title":"MelancholyIII","artist":"Munch","year":1902,"type":1}{"_id":3,"title":"Dancer","artist":"Miro","year":1925,"type":1}{"_id":4,"title":"TheGreatWaveoffKanagawa","artist":"

我有以下文档结构{"timestamp":13512493603565120,"value":1,"y":42,"M":513,"w":2234,"d":15639,"S":46918,"h":375347,"m":22520822,"s":1351249360,"_id":ObjectId("508aa61100b5457c04000001"),"__v":0}我有一个如下的mongodb聚合来汇总按字段y分组的值:aggregate({$group:{_id:"$y",value:{$sum:4}}})这会给我[{"_id":42,"value":16}]我现在想要的是格式化此输出

假设我有一个包含员工文档的MongoDB集合:{name:"JohnDoe",department:"Finance",salary:100}如何查询每个部门薪资最高的X名员工？编辑为了让自己更清楚一点，我是这样想的:db.collection.aggregate({$sort:{salary:-1}},{$group:{_id:"$department"employees:{$addToSet:"$name"}},{$project:{employees:{$slice:X}}})但这行不通有两个原因:1.$addToSet不保证输出集的任何顺序(至少根据documentation)

我希望使用mongoDB的聚合框架获得特定的查询。我想我需要$group和$addToSet运算符，但我对要使用的正确查询感到困惑。这是文章合集:/*0*/{"_id":4,"author":"KevinVanhove","book":{"order":500,"title":"HTML","url":"html"},"chapter":{"img":"navChapter-logo","order":500,"title":"W3C","url":"w3c"},"featured":0,"heading":[{"title":"title1","_id":ObjectId("5313

我有一个这样的文件集:{"Company":"4433","Descripcion":"trabajo","Referencia":"11817","HoraImportado":"15:54","ImportedOd":"2014-05-20T13:54:28.493Z","Items":[],"Notes":[{"_id":ObjectId("537b5ea4c61b1d1743f43420"),"NoteDateTime":"2014-05-20T13:54:44.418Z","Description":"nota","IsForTechnician":true,"Usernam

我需要对数组出现的次数求和。我需要将其输出到一个集合中，但是当我尝试使用$out关键字时，它失败并显示“不能将数组用于_id\”有没有办法将小组赛阶段的_id字段的值投影到一个新的key中，并创建一个新的_id？db.djnNews_filtered.aggregate([{$unwind:"$processed_text.headline_trigrams"},{$group:{_id:"$processed_text.headline_trigrams","num":{$sum:1}}},{$sort:{"num":-1}}]){"_id":["Reports","First","

考虑数据集{"_id":{"$oid":"aaa"},"student_id":0,"type":"exam","score":54.6535436362647}{"_id":{"$oid":"bbb"},"student_id":0,"type":"quiz","score":31.95004496742112}{"_id":{"$oid":"ccc"},"student_id":0,"type":"homework","score":14.8504576811645}{"_id":{"$oid":"ddd"},"student_id":0,"type":"homework","sc

我在MongoDB中有以下场景:每条记录都有自己的_id和parentId。如果parentId==""那么它就是一个真正的父记录。如果parentId有一个值，那么该记录实际上是一个指向父记录的子记录。下面显示了一个父项及其链接的子项。{"_id":ObjectId('586c9d275d2f62e1634978db'),parentId="",count=1,}{"_id":ObjectId('586c9d275d2f62e163497811'),parentId=ObjectId('586c9d275d2f62e1634978db'),count=3,}我想要一个查询，在那里我找

编辑:此编辑可能会改变此问题的进程。在spark上运行的mongodb聚合(特别是$group)在写回集合时创建了重复的_id记录。结果，mongodb抛出重复键错误。顺便说一句，这个查询在mongoshell中运行得很好。这是我做的:我拿了一个小数据集，并将(聚合)spark代码的结果打印到控制台，而不是写入集合。我打印了完整的结果集，但在_id字段中发现了重复项。数据看起来像这样:(已编辑)Document{{_id=Document{{prodCategory=123},{proId=ABC},{‌​location=US}},details=[Document{{....}},

我读过SO和类似的问题one.但是我无法构建我想要的查询...假设我有以下数据结构:{"CAUG":"id1","action":"actionA","date":ISODate("2017-01-01"),"hp":16}{"CAUG":"id1","action":"actionB","date":ISODate("2017-01-01"),"hp":17}{"CAUG":"id1","action":"actionC","date":ISODate("2017-02-10"),"hp":18}{"CAUG":"id2","action":"actionX","date":ISOD