MongoDB : How can I project all field types for a single document?

Question

我需要检查给定集合中每个文档中的每个字段类型。

虽然我可以为每个字段编写单独的 $type 命令并分别匹配每个文档，但我想知道是否有一种更优雅、更有效的方法来投影所有字段类型。

Answer 1

试试这个:

db.collection.aggregate([{
    $addFields: {
        types: {
            $arrayToObject: {
            $map:
            {
                input: { $objectToArray: "$$ROOT" },
                as: "each",
                in: { k: '$$each.k', v: { $type: '$$each.v' } }
            }
        }}
    }
}])

收集数据:

/* 1 */
{
    "_id" : ObjectId("5e065992400289966eefb9a8"),
    "username" : "myName",
    "blog" : "myBlog",
    "details" : "myBlogDetails",
    "Object" : {
        "inOneObject" : true
    }
}

/* 2 */
{
    "_id" : ObjectId("5e0659ae400289966eefbc3a"),
    "username" : "othersName",
    "blog" : "not a blog",
    "details" : "useless"
}

结果:

/* 1 */
{
    "_id" : ObjectId("5e065992400289966eefb9a8"),
    "username" : "myName",
    "blog" : "myBlog",
    "details" : "myBlogDetails",
    "Object" : {
        "inObject" : true
    },
    "types" : {
        "_id" : "objectId",
        "username" : "string",
        "blog" : "string",
        "details" : "string",
        "Object" : "object"
    }
}

/* 2 */
{
    "_id" : ObjectId("5e0659ae400289966eefbc3a"),
    "username" : "othersName",
    "blog" : "not a blog",
    "details" : "useless",
    "types" : {
        "_id" : "objectId",
        "username" : "string",
        "blog" : "string",
        "details" : "string"
    }
}

注意:此给定查询仅适用于文档中的顶级字段，它不会从下面的字段中获取 inObject 类型::

"Object" : {
            "inOneObject" : true
        }