从mongodb中的周数获取一周的第一天

Question

我有包含日期​​字段的集合。我正在按周和其他相关领域对记录进行分组。

这是我的聚合查询：

db.raw.aggregate([
    { "$match" : {
        "Timestamp":{
            "$gte": new Date("2012-05-30"), 
            "$lt": new Date("2014-07-31")
        }
    }},
    { "$group" : {
        "_id":{ 
            "ApplicationId": "$ApplicationId",
            "Country": "$Country",
            "week":{ "$week": "$Timestamp" }
        },
        "Date":{ "$first": "$Timestamp" },
        "Visits": { "$sum": 1 }
    }}
])

我想从周数预测：访问次数和一周的开始日期。

Answer 1

对于 mongo >= v3.4，请查看 weekStart。这个想法是从给定的时间戳中减去毫秒

db.raw.aggregate([
         // stage 1
        { "$match" : {
            "Timestamp":{
                "$gte": ISODate("2012-05-30"), 
                "$lt": ISODate("2014-07-31")
            }
        }},

         // stage 2
        { "$project" : {

           ApplicationId: 1,
           Country: 1,
           week: {$isoWeek: "$Timestamp"},

           // [TRICK IS HERE] Timestamp - dayOfWeek * msInOneDay
           weekStart: { $dateToString: { format: "%Y-%m-%d", date: { // convert date
             $subtract: ["$Timestamp", {$multiply: [ {$subtract:[{$isoDayOfWeek: "$Timestamp"},1]}, 86400000]}] 
           }}},

         // stage 3
        { "$group" : {
        "_id":{ 
            "ApplicationId": "$ApplicationId",
            "Country": "$Country",
            "week": "$week"
        },
        "Date":{ "$first": "$weekStart" },
        "Visits": { "$sum": 1 }
        }}        
 ])