DataWeave groupBy和maxBy

Question

我是个DataWeave新手。我试图为用户获取最新的扣减记录，但也按数组中的类型分组。这是我必须处理的数据：

"users": [
    {
        "employeeId": "123456",
        "lastName": "smith",
        "firstName": "joe ",
        "deductions": [
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2001-01-02T00:00:00"
            },
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2019-01-02T00:00:00"
            },
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2016-01-02T00:00:00"
            },
            {
                "deductionType": "DCA",
                "Amt": 4000,
                "StartDate": "2019-11-02T00:00:00",
            }
        ]
    }

我尝试使用类似的解决方案：Dataweave 2.0 maxBy and filter，但这似乎不起作用，因为我得到了一个空的有效负载。

最终结果应该如下所示：

    "users": [
    {
        "employeeId": "123456",
        "lastName": "smith",
        "firstName": "joe ",
        "deductions": [
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2019-01-02T00:00:00"
            },
            {
                "deductionType": "DCA",
                "Amt": 4000,
                "StartDate": "2019-11-02T00:00:00",
            }
        ]

我目前试图解决的办法是：

    payload.users map {($),
               deductions: (($.deductions groupBy $.deductionType) mapObject (value, key) -> 
                            {(key) : (value maxBy $.benefitStartDate)}) pluck (value) -> value

}

但这也没用。

Answer 1

尝尝这个

{ 
    users: payload.users map {
        ($ - "deductions"),
        deductions: (($.deductions groupBy $.deductionType) pluck $) map {
            ($ maxBy $.StartDate)
        }
    }
}

Answer 2

这里有一个不同的解决方案，使用性能更好的解决方案:)。该算法的注释可以在DW表达式中看到。此外，我在代码中硬编码了示例数据，因此您只需要复制和粘贴就可以使DW表达式工作。

%dw 2.0
output application/dw

var data = "users": [
    {
        "employeeId": "123456",
        "lastName": "smith",
        "firstName": "joe ",
        "deductions": [
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2001-01-02T00:00:00"
            },
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2019-01-02T00:00:00"
            },
            {
                "deductionType": "ABC",
                "Amt": 1000,
                "StartDate": "2016-01-02T00:00:00"
            },
            {
                "deductionType": "DCA",
                "Amt": 4000,
                "StartDate": "2019-11-02T00:00:00",
            }
        ]
    }
]
---
users: data.users map do {
    // Sort by StartDate, I type casted to a `DateTime` instead of comparing strings
    // Reverse the sorted list such that the latest dates are at the top of the list
    // Finally, get a set out the list where uniqueness is the deductionType
    //   since distinctBy maintains the first element that matches and removes the rest
    //   you know have a list of distinct deductionType with the latest date.       
    var ds = ($.deductions orderBy ($.StartDate as DateTime))[-1 to 0]
              distinctBy (d) -> d.deductionType
    ---
    {
        ($ - "deductions"),
        deductions: ds
    }
}