猫鼬查找查询与 $match

问题描述

我在 mongodb 中有以下文档

I have a following document inside mongodb

{
    "_id" : ObjectId("5a25f1b19c72e07ffc50a37d"),
    "name" : "test",
    "category" : ObjectId("5a1e6622a7739fb64c8c530b"),
    "recentDeveloperComment" : ObjectId("5a25f1b19c72e07ffc50a37c"),
    "fileName" : "test2.xlsx",
    "rawData" : ObjectId("5a21079ef99e75b2140fb77a"),
    "group" : {
        "year" : 2017,
        "month" : 1,
        "category" : "test1"
    },
    "unlocked" : false,
    "status" : "Pending",
    "updatedAt" : ISODate("2017-12-05T01:08:40.465Z"),
    "createdAt" : ISODate("2017-12-05T01:08:40.465Z"),
    "__v" : 0
}

我可以通过使用下面的 mongoose 查找查询来匹配这个

I can match this by using following find query with mongoose

Repo.find({'group.year' : year, 'group.month' : month, 'group.category' : category, name:repo})
    .exec((err, repoResult) => {
        //matches one document
    })

但是使用下面的聚合 $match 我不能得到相同的结果

However with the below aggregate $match I cannot get the same result

Repo.aggregate([
    {
        $match:
            {
                $and:[
                    {'group.year' : year},
                    {'group.month' : month},
                    {'group.category' : category},
                    {name : repo}
                ]
            }
    },
]).exec((err, commitsResult) => {
    //matches zero document
});

这是为什么?

推荐答案

这是因为 find 将所有查询字符串解析为数据库中定义的变量类型.例如 year 是一个从 url 解析出来的参数，所以它是一个字符串形式，但在 Mongodb 中，该字段被定义为一个 int.Find 会自动将其解析为正确的类型，但 $match 不会解析它，因此必须手动完成.

It was because find parses all the query strings into the variable type that is defined in the database. For example year was a parameter parsed from url so it was a string form but in Mongodb the field is defined as an int. Find automatically parses this to the correct type but $match does not parse it so it has to be done manually.

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