投影到 child 的字段

Question

Spring 1.3.6，使用 spring-data mongodb

有这样的文档：

{
  "name":"Dmitry",
  "props":{
    "city":"Moscow"
    "age":"26"
  }
}

想要这样的东西通过 spring mongo 投影

{
  "city":"Moscow",
  "person":{
    "name":"Dmitry",
    "age":"26"
   }
}

试过这个聚合操作

Aggregation aggregation = newAggregation(
    project().and("name").as("person.name")
        .and("props.city").as("city")
        .and("props.age").as("person.age")
);
AggregationResults<DBObject> results = this.mongoTemplate.aggregate(aggregation, MyType.class, DBObject.class);
results.getMappedResults();

有这样的结果

{
  "city":"Moscow",
  "name":"Dmitry",
  "person":{  
    "age":"26"
   }
}

可以将字段绑定为另一个名称的字段，将 child 字段绑定到 parent 字段，将 child 字段绑定到另一个 child，但是我没有成功通过 mongo 投影将 parent 字段绑定到 child。

Answer 1

打印生成的聚合查询，看看它是否匹配下面的查询。

db.Whosebug.aggregate([{$project:{"person.name": "$name", city:"$props.city", "person.age":"$props.age"}}]).pretty();

当我执行查询时，我得到了以下结果

{
        "_id" : ObjectId("57b32a0fc516d5b5c94cae0d"),
        "person" : {
                "name" : "Dmitry",
                "age" : "26"
        },
        "city" : "Moscow"
}
{
        "_id" : ObjectId("57b32b59c516d5b5c94cae0e"),
        "person" : {
                "name" : "Roseline",
                "age" : "22"
        },
        "city" : "Berlin"
}

这些是我的记录collection

db.Whosebug.find().pretty();
{
        "_id" : ObjectId("57b32a0fc516d5b5c94cae0d"),
        "name" : "Dmitry",
        "props" : {
                "city" : "Moscow",
                "age" : "26"
        }
}
{
        "_id" : ObjectId("57b32b59c516d5b5c94cae0e"),
        "name" : "Roseline",
        "props" : {
                "city" : "Berlin",
                "age" : "22"
        }
}

希望对您有所帮助！！

Answer 2

这是使用投影的 Spring 代码。您可能需要根据从 Spring 上下文获取 MongoOperations 对象的方式替换此代码 "getMongoConnection()"。

聚合方法使用投影：-

public Boolean aggregateMyTypeCollectionUsingProject() {

        MongoOperations mongoOperations = getMongoConnection();

        ProjectionOperation  project = Aggregation.project().and("props.city").as("city").and("props.age").as("person.age").andExpression("name")
                .as("person.name");
        Aggregation aggregate = Aggregation.newAggregation(project);

        System.out.println(aggregate.toString());
        AggregationResults<DBObject> results = mongoOperations.aggregate(aggregate, MyType.class, DBObject.class);

        System.out.println("Result ============>" + results.getMappedResults());
        return true;

    }

我的 getMongoConnection() 方法：-

@SuppressWarnings("resource")
public MongoOperations getMongoConnection() {

    return (MongoOperations) new AnnotationConfigApplicationContext(SpringMongoConfig.class)
            .getBean("mongoTemplate");
}

查询:-

{ "aggregate" : "__collection__" , "pipeline" : [ { "$project" : { "city" : "$props.city" , "person.age" : "$props.age" , "person.name" : "$name"}}]}

输出：-

{
    "_id": {
        "$oid": "57b32d31ced49443e4b79f0d"
    },
    "city": "Moscow",
    "person": {
        "age": "26",
        "name": "Dmitry"
    }
}

投影到 child 的字段

Projection to child's field

spring

mongodb

spring-data

projection