MongoDB Spring Data-按引用对象属性排序

Question

I search a lot trying to do what I want to do and can't find a solution. Can anyone help me?

I have two Mongo Collections:

A. Post

{
    content: "...",
    user: {
        $ref: "user",
        $id: ObjectId(...)
    }
}

B. User

{
    name: "user name",
    age: 21
}

And I want to list all the posts sorted by User name, can I do it?

I tried something like that:

Query query = new Query();
query.with(new Sort(new Sort.Order(Sort.Direction.ASC, "user.name")));
return mongoTemplate.find(query, Post.class);

But doesn't work, how can I do?

Answer 1

MongoDB is only a document store by design, you can use it like a relational DB, if you have to something like this, either

• MongoDB is not for you
• Or you need get both collections and join them manuell

Answer 2

With this schema you can't sort posts by user name in one atomic operation. You have some choices:

1. Use user names in field user and make sure that you have index on field name in users colection, so you can sort posts by user names in one operation and you will increase performance by using indexes.
2. If you don't want to change schema, so try to use mongo aggregation framework.