英文:
Mongo DB and Go - using dynamic data models
问题
我面临一个问题，不确定应该选择哪条路。所以我在这里问一下。我有一个应用程序，其中可以有产品，也可以有产品的元数据。这些元数据可以在前端创建和删除。假设今天每个产品有两个元数据（例如名称、价格），那么明天可能是三个、四个或更多，甚至少于两个。所以这是动态的。我试图将数据表示如下：
产品 =
{
"_id": mongo
"名称": 字符串
"描述": 字符串
"基础价格": 数字
"创建者": 用户 mongo _id
"创建时间": 时间戳
"修改时间": 时间戳
"元数据": BSON 对象（包含来自 ProductMetadata 集合的所有键和它们的值。例如：{"类别": "餐具"，"材料": "橡木、铜"，"长度": 5.6}）
}
产品元数据 =
{
"_id": mongo
"名称": 字符串（例如 - "类别" 或 "材料" 或 "高度"）
"类型": 字符串（指示它可以保存的值的类型，如字符串/整数/数组。例如 - "字符串"）
"创建时间": 时间戳
"修改时间": 时间戳
}
如你所见，这是一个纯动态的情况，所以在代码层面上表示模型的结构是不可能的。
我的问题是，我如何使用 mgo 和 Go 语言来实现这样的功能？如果我需要使用反射，请有人指点我一个好的博客/教程，我可以在那里获取更多信息。或者如果你认为在建模数据的方法上存在根本性问题，请纠正我，以便可以轻松地使用 Go 实现。
在 Python 中，实现这个不是问题。我知道这一点。但是我对 Go 的实现感到困惑。
请帮忙。
提前感谢。
英文:
I am faced with a problem where I am not sure which path to take. So I am asking it here. I have an application where there can be products and there can be metadata for a product. These metadata can be created and deleted from the front end. So let's say, today a each product has two meta data (e.g. Name, Price) then tomorrow it can be three, four or more or even less than two. So this is dynamic. I am trying to represent the data as follows
Product =
{
"_id": mongo
"Name": string
"Description": string
"BasePrice": number
"CreatedBy": user mongo _id
"CreatedAt": timestamp
"ModifiedAt": timestamp
"MetaData": BSON object (having all the keys from ProductMetadata collection and their values. e.g. {"Category": "table ware", "Material": "oak wood, copper", "Length": 5.6})
}
ProductMetadata =
{
"_id": mongo
"Name": string (e.g. - "Category" or "Material" or "Height")
"Type": string (indicating what kind of value it can hold like string/integer/array. e.g. - "string")
"CreatedAt": timestamp
"ModifiedAt": timestamp
}
As you can see this is a pure dynamic situation so having a structure at the code level which represent the model is impossible.
My problem is, how do I implement such a thing using mgo and Go lang? If I need to use reflection then can some one please point me towards a good blog/tutorial where I can get a little bit more info. Or if you think that there is a fundamental problem in the approach of modeling the data then please correct me so that it can be easily implemented using Go.
In Python, it would not be a problem to implement this. I know that. But I am confused about the Go implementation.
Please help.
Thanks in advance
答案1
得分: 3
如果元数据的键是唯一的，为什么不直接使用一个映射（map）呢？
也就是说，你的Product结构体看起来像这样：
struct Product {
ID bson.ObjectId `bson:"_id,omitempty"`
Name string
Description string
... 省略其他字段 ...
MetaData map[string]map[string]interface{} // 字符串到字符串到任意类型的映射
}
如果你可以有多个相同元数据的实例，比如2个类别，可以使用一个列表（list）：
struct Product {
ID bson.ObjectId `bson:"_id,omitempty"`
Name string
Description string
... 省略其他字段 ...
MetaData []map[string]interface{} // 字符串到任意类型的映射的列表
}
英文:
If Keys for metadata are unique, why not just use a map.
meaning your Product struct looks like:
struct Product {
ID bson.ObjectId `bson:"_id,omitempty"`
Name string
Description string
... omitted other fields ...
MetaData map[string]map[string]interface{} // map of string -> map of string -> anything
}
If you can have more than one instance of a given meta data, ie: 2 categories, use a list:
struct Product {
ID bson.ObjectId `bson:"_id,omitempty"`
Name string
Description string
... omitted other fields ...
MetaData []map[string]interface{} // list of maps of string -> anything
}
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