pymongo中使用map减少时的NumberDecimal和问题

Question

我尝试对所有我的金额值求和，这些值作为NumberDecimal数据类型存储在mongodb中。

这是我编写的map reduce代码。

        mapper = """
        function() {
            const key = this.time.toLocaleDateString('zh-CN');
            emit(key, {
                ids: [this.distinct_id],
                unique: 1,
                count: 1,
                date: key,
                avg: 0,
                amount: this.amount, // the amount I want to sum
            });
        }
    """
    reducer = """
    function (key, values) {
        const idset = new Set();
        var count = 0;
        var amount = 0;

        values.forEach(value => {
            value.ids.forEach(id => { idset.add(id); });
            count += value.count;
            amount += value.amount; // here I added all up.
        });

        return {
            ids: Array.from(idset),
            unique: idset.size,
            count: count,
            date: key,
            amount: amount,
        }
    }
    """

这是我得到的结果。似乎所有的值都由字符串连接起来！

{data: [{
   amount: "0000000NumberDecimal("1486.72")NumberDecimal("1572.06")NumberDecimal("720.04")NumberDecimal("276.23")....."
]}