mongo聚合

db.getCollection('xxx').aggregate([
    {$match:{"dt":"20191x10109","mediaId":101}},
    {$group:{_id:null, count:{$sum:"$click"}}}
])

db.getCollection('xxx').aggregate(
[
                       { $match : {"dt":"20191004", "customerId":"158892"} },
                        { $group: { _id:"$customerId", "totalCost":{$sum: "$cost"} }} 
                       ]
)

map_reduce 聚合
db = client.get_database('xxx')
coll = db['material_video_data']
mapper = Code("""
            function() { emit(this.fileMd5, this.cost);}
        """)
reducer = Code("""
            function(key, values) { 
                totalsum = 0;
                for(i=0;i<values.length;i++){
                    totalsum+=parseFloat(values[i]);
                    }
                return totalsum}
        """)
momgo_result = coll.map_reduce(mapper, reducer, "myresult", query={"dt": self.dt},timeout=False)

操作MongoDB数据库，批量化地将某一属性的某一值更改为同一属性的另外一个值，如将status:2更改为status:0

>db.zgd_total_dataset.update({status:2},{$set:{status:0}}, false, true)