Question

我遇到了这段代码的问题。（使用节点，express，mongoose将文件保存到mongodb）

// We have an array that contains objects (365) of type 'Day' to be stored in mongodb. 
// In my code this array contains data :-)
let arrDays = []

// Empty array to hold reference to the _id of the created days
let arrDaysID = [];

// Store all days in the 'arrDays' array to mongodb using mongoose
Day.create(arrDays, function(err, days){
    if(err){
        console.log("Something went wrong " + err)
    } else {
        // Iterate over every 'day' object in mongodb and add a reference to           
        // the _id of the 'day' object inside the 'year' object
        days.forEach(function(day){
            year.days.push(day._id);
            year.save();
        });
    }
});

问题是，不是在'year'对象中添加每个_id引用一次，而是多次添加_id引用。代码运行完毕后，year.days数组中有大约140,000个引用，而定义只有365天...

欢迎任何提示或提示。

戴夫

Answer 1

根据model.create API的documentation，它是Shortcut for saving one or more documents to the database. MyModel.create(docs) does new MyModel(doc).save() for every doc in docs.

这意味着，您正在为create方法中添加的每一天执行forEach循环，使其成为一个n * n复杂函数。

365 * 365 = 133225大约等于140000条记录。

我认为这解释了这个问题。

编辑 - 更好的选择

根据mongoose insertMany API，Model.insertMany()比Model.create because it only sends one operation to the server, rather than one for each document

更快

mongodb参考文件

1 个答案: