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" : "kerala", "district" : "palakkad", "pincode" : "5203689", }, "place_lat" : "18", "place_lan" : "83", } ] } ] }
我有另一个places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 aggResults = mongoTemplate.aggregate(aggregation, PersonAddressDocument.class, OutputDocument.class);
谁能帮我？
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" }, { "$lookup": { "from": "places", "localField": "address.location.place._id", "foreignField": "_id", "as": "address.location.place", } } ])
然后可以实现为（未经测试）：
LookupOperation lookupOperation = LookupOperation.newLookup() .from("places") .localField("address.location.place._id") .foreignField("_id") .as("address.location.place"); Aggregation agg = newAggregation( unwind("address"), unwind("address.location"), lookupOperation ); AggregationResults aggResults = mongoTemplate.aggregate( agg, PersonAddressDocument.class, OutputDocument.class );
如果您的Spring Data版本不支持此function，则解决方法是实现AggregationOperation接口以接收DBObject ：
public class CustomGroupOperation implements AggregationOperation { private DBObject operation; public CustomGroupOperation (DBObject operation) { this.operation = operation; } @Override public DBObject toDBObject(AggregationOperationContext context) { return context.getMappedObject(operation); } }
然后在聚合管道中将$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 aggResults = mongoTemplate.aggregate( agg, PersonAddressDocument.class, OutputDocument.class );