finalize:function(result) { result.avg=result.sum/result.cnt;//求平均 } }) 2 aggregate 2.1 定义 MongoDB中聚合(aggregate)主要用于处理数据(诸如统计平均值,求和等),并返回计算后的数据结果 基本语法: db.collection.aggregate(docment); 具体方法实例有:$match,$project,$group,$unwind,$sort,$limit,$sk...
dengqs@mongodbServer:~# ./mongo MongoDB shell version: 1.8.3 connecting to: test > help db.help() help on db methods db.mycoll.help() help on collection methods rs.help() help on replica set methods help connect connecting to a db help help admin administrative help help misc misc t...
db.users.find({age: {$lte: 28}}, {age: false}).forEach(printjson); 1. 9、forEach传递函数显示信息 db.things.find({x:4}).forEach(function(x) {print(tojson(x));}); 1.
changed in version 5.0 . name description returns the result of a user-defined accumulator function. returns an array of unique expression values for each group. order of the array elements is undefined. changed in version 5.0 : available in the $setwindowfields stage. returns an average of ...
当所有的shards都处理完毕后,mongos将处理结果返回给客户端(inline)。 mapReduce 语法格式: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 db.collection.mapReduce(,<reduce>,{out:<collection>,query:<document>,sort:<document>,limit:<number>,finalize:<function>,scope:<document>,jsMode:<boolean>...
Mongo代码如下: 1>db.posts.group({23… “key” : {“day” :true},45… “initial” : {“tags” : {}},67… “$reduce” :function(doc, prev) {89…for(iindoc.tags) {1011…if(doc.tags[i]inprev.tags) {1213… prev.tags[doc.tags[i]]++;1415… }1617…else1819… {2021… prev....
NoSQL数据库学习之MongoDB之group by 限制 如果你用group 命令的话可能会遇到下面两种错误: a.)命令:db.flogsamplelog.group({cond:{datetimes":20111027},key:{"pid":"1"},initial:{"count":0},reduce:function(doc,prev){if(doc.pid==prev.pid)prev.count++;}})...
type、enabled// 设置资源组类型、启用状态set_type、set_enabled// 设置、返回资源组的控制对象set_controller、controller// 传入类型为std::function<void(ulonglong)>的控制方法,对m_pfs_thread_id_set中所有thread实施控制apply_control_func// 添加、移除pfs thread idadd_pfs_thread_id、remove_pfs_thread_...
db.TruckUsers.group({ key:{PhoneNumber:true}, initial:{Count:0}, reduce:function(doc,prev) { if (!prev.PhoneNumber) { prev.PhoneNumber = doc.PhoneNumber; prev.Count = 1; } else if(doc.PhoneNumber == prev.PhoneNumber) { prev.Count++; } }, finalize:function(doc) { for(i in do...
{ $group: { _id: '$content', count: { $sum: 1 } } }, { $match: { count: { $gt: 1 } } }, { $sort: { count: -1 } } ] ).toArray(function(err, result) { console.log(result); }); [ { _id: '猜谜底', count: 7 }, ...