mongodb - Spring MongoDB 聚合 DBRef

Question

我有 spring mongoDB 集合用户，数据如下:

    [{
  "_id": {
    "$oid": "5fd81fb277b245717d34c25e"
  },
  "userName": "banana",
  "email": "banana",
  "userRole": {
    "$ref": "roles",
    "$id": {
      "$oid": "5fdc248b1846a46d71a71374"
    }
  }
},{
  "_id": {
    "$oid": "5fd81fd777b245717d34c25f"
  },
  "userName": "banana",
  "email": "banana",
  "userRole": {
    "$ref": "roles",
    "$id": {
      "$oid": "5fd6e784f03b1f5e76699ebb"
    }
  }
},{
  "_id": {
    "$oid": "5fdc24691846a46d71a71373"
  },
  "userName": "banana",
  "email": "banana",
  "userRole": {
    "$ref": "roles",
    "$id": {
      "$oid": "5fd6e784f03b1f5e76699ebb"
    }
  }
},{
  "_id": {
    "$oid": "5fe19f2f136f696e0bf83167"
  },
  "userName": "banana",
  "email": "banana",
  "userRole": {
    "$ref": "roles",
    "$id": {
      "$oid": "5fdc248b1846a46d71a71374"
    }
  }
}]

我尝试使用 Spring MongoDB 对其应用聚合

GroupOperation groupOperation = Aggregation.group("userRole.$id")
                .addToSet("email").as("email")
                .addToSet("firstName").as("firstName");

        Aggregation aggregation = Aggregation.newAggregation(groupOperation);

        AggregationResults<Map> result = mongoOperations
                .aggregate(aggregation, "user", Map.class);
        return result.getMappedResults();

但是它不起作用。我的问题是 Spring MongoDB Aggregation 支持 DBref 吗？

Answer 1

Spring data mongo确实支持聚合，您可以在这里阅读更多相关信息 - https://www.baeldung.com/spring-data-mongodb-projections-aggregations

根据您提供的集合示例，我没有看到任何名为 firstName 的字段，您是否可能指的是 userName 并基于您的聚合我们提供的是否与此类似:

db.collection.aggregate({
  "$group": {
    "_id": {
      "userRole": "$userRole.$id"
    },
    "email": {
      "$addToSet": "$email"
    },
    "username": {
      "$addToSet": "$userName"
    }
  }
})

如果是这样，那么您可以直接将此管道添加到您的存储库方法中。像这样的事情

public interface UserRepository extends MongoRepository<User, String> {
    
     @Aggregation(pipeline = {
        "{ \"$group\": { \"_id\": { \"userRole\": \"$userRole.$id\" }, \"email\": { \"$addToSet\": \"$email\" }, \"username\": { \"$addToSet\": \"$userName\" } } }"
     })
     AggregationResults<Result> findAndGroup();
}

*注意 - 这里 Result 是具有与返回文档等效的字段的类

然后

@Autowired
private UserRepository userRepository;

userRepository.findAndGroup().getMappedResults();