mongodb聚合函式時間如果是date型別的 分組的話會出現時區相差8小時問題,因為$dayOfYear等函式是按照utc時間分組的 所以會有問題,

解決方法1:

時間地段用字串儲存,然後利用$substr來擷取 年月日進行按天分組等 程式碼如下

db.main_test.aggregate(
    {
        $project: {
            time: '$time',
            timeFormat: { $dateToString: { format: "%Y-%m-%d", date: "$time" } },
            timeYearStr: { $substr: ['$time', 0, 4] },
            timeMonthStr: { $substr: ['$time', 5, 2] },
            timeDayStr: { $substr: ['$time', 8, 2] },
            year: { $year: "$time" },
            month: { $month: "$time" },
            day: { $dayOfMonth: "$time" },
            request: '$request'
        }
    },
    {
        $match: {
            time: { $gte: new Date('2017-03-13'), $lte: new Date('2017-03-15') }
        }
    },
    {
        $group: {
            _id: { year: '$year', month: '$timeMonthStr', day: '$timeDayStr' },
            time: { $last: "$time" },
            timeFormat: { $last: "$timeFormat" },
            timeYearStr: { $last: "$timeYearStr" },
            timeMonthStr: { $last: "$timeMonthStr" },
            timeDayStr: { $last: "$timeDayStr" },
            totalReq: { $sum: "$request" }
        }
    },
    { $sort: { time: 1 } }
)

解決方法2:時間還是date型別 使用 $add:['$time',28800000]後再進分組

如下:

db.main_test.aggregate(
    {
        $project: {
            time: '$time',
            timeNew:  { $substr:[{$add:['$time',28800000]},0,10]},
            timeFormat: { $dateToString: { format: "%Y-%m-%d", date: "$time" } },
            timeYearStr: { $substr: ['$time'.toLocaleString(), 0, 4] },
            timeMonthStr: { $substr: ['$time', 5, 2] },
            timeDayStr: { $substr: ['$time', 8, 2] },
            year: { $year: "$time" },
            month: { $month: "$time" },
            day: { $dayOfMonth: {$add:['$time',28800000]} },
            request: '$request'
        }
    },
    {
        $match: {
            time: { $gte: new Date('2017-03-13'), $lte: new Date('2017-03-15') }
        }
    },
    {
        $group: {
            _id: { year: '$year', month: '$timeMonthStr', day: '$day' },
            day:{$last:'$day'},
            timeNew:{$last:'$timeNew'},
            time: { $last: "$time" },
            timeFormat: { $last: "$timeFormat" },
            timeYearStr: { $last: "$timeYearStr" },
            timeMonthStr: { $last: "$timeMonthStr" },
            timeDayStr: { $last: "$timeDayStr" },
            totalReq: { $sum: "$request" }
        }
    },
    { $sort: { time: 1 } }
)
 

參考連結:https://docs.mongodb.com/manual/reference/operator/aggregation/substr/