java – 在mongodb聚合中查找

以下bson是personaddress集合：{ id : 123456, name : foo, address : [{local : yes, location : [{place : {_id:VZG, }, place_lat : 18, place_lan : 83, },{place : {name : ...

以下bson是personaddress集合：

{ 
        "id" : "123456", 
        "name" : "foo", 
        "address" : [
            {
                "local" : "yes", 
                "location" : [
                   {
                        "place" : {
                            "_id":"VZG", 

                        }, 
                        "place_lat" : "18", 
                        "place_lan" : "83", 

                },
                {
                        "place" : {
                            "name" : "kerala", 
                            "district" : "palakkad", 
                            "pincode" : "5203689", 

                        }, 
                        "place_lat" : "18", 
                        "place_lan" : "83",      
                    }
                ]
            }
        ]
    } 

我有另一个地方集合：

 {
     "_id":"VZG",
     "name" : "vizag", 
     "district" : "Visakhaptanam, 
     "pincode" : "568923",
 }

在mongodb聚合中使用lookup,我想在personaddress集合中嵌入places集合

我试过用

Aggregation aggregation = newAggregation(lookup("places", "address.location.place._id", "_id", "myplaces"), unwind("myplaces"));

AggregationResults<OutputDocument> aggResults = mongoTemplate.aggregate(aggregation, PersonAddressDocument.class, OutputDocument.class);

谁能帮我？

解决方法:

由于您具有嵌套数组,因此在使用$lookup管道之前,需要首先应用$unwind运算符以使嵌入文档非规范化(除非您已在聚合操作中将它们展平)：

db.personaddress.aggregate([
    { "$unwind": "$address" },
    { "$unwind": "$address.location" },
    {
        "$lookup": {
            "from": "places", 
            "localField": "address.location.place._id", 
            "foreignField": "_id", 
            "as": "address.location.place", 
        }
    }
])

然后可以实现为(未经测试)：

LookupOperation lookupOperation = LookupOperation.newLookup()
    .from("places")
    .localField("address.location.place._id")
    .foreignField("_id")
    .as("address.location.place");

Aggregation agg = newAggregation(
    unwind("address"),
    unwind("address.location"),
    lookupOperation  
);

AggregationResults<OutputDocument> aggResults = mongoTemplate.aggregate(
    agg, PersonAddressDocument.class, OutputDocument.class
);

如果您的Spring Data版本不支持此功能,则解决方法是实现AggregationOperation接口以接收DBObject：

public class CustomGroupOperation implements AggregationOperation {
    private DBObject operation;

    public CustomGroupOperation (DBObject operation) {
        this.operation = operation;
    }

    @Override
    public DBObject toDBObject(AggregationOperationContext context) {
        return context.getMappedObject(operation);
    }
}

然后在聚合管道中将$lookup操作实现为DBObject：

DBObject lookupOperation = (DBObject)new BasicDBObject(
    "$lookup", new BasicDBObject("from", "places")
        .append("localField", "address.location.place._id")
        .append("foreignField", "_id")
        .append("as", "address.location.place")       
);

您可以将其用作：

Aggregation agg = newAggregation(
    unwind("address"),
    unwind("address.location"),
    lookupOperation  
);

AggregationResults<OutputDocument> aggResults = mongoTemplate.aggregate(
    agg, PersonAddressDocument.class, OutputDocument.class
);