Return nested elements in Json that equal search string - mongodb

Question

I has the following json document in Mongo db. The show element will have several season elements which will also have several episodes elements that in turn have multiple questionEntry elements.

I want to return multiple questionElements where the questionElements metaTag entry equals my search. E.G. if a metaTag element equals my string the return it's parent questionEntry element and search across all elements nested in show.

{
"show":[
  {
     "season":[
        {
           "episodes":[
              {
                 "questionEntry":{
                    "id":1,
                    "info":{
                       "seasonNumber":1,
                       "episodeNumber":5,
                       "episodeName":"A Hero Sits Next Door"
                    },
                    "questionItem":{
                       "theQuestion":"What is the name of the ringer hired by Mr. Weed?",
                       "attachedElement":{
                          "type":1,
                          "value":""
                       }
                    },
                    "options":[
                       {
                          "type":1,
                          "value":"Johnson"
                       },
                       {
                          "type":1,
                          "value":"Hideo"
                       },
                       {
                          "type":1,
                          "value":"Guillermo"
                       }
                    ],
                    "answer":{
                       "questionId":1,
                       "answer":3
                    },
                    "metaTags":[
                       "Season 1",
                       "Episode 5",
                       "Trivia",
                       "Arya Stark",
                       "House Stark"
                    ]
                 }
              }
           ]
        }
     ]
   }
 ]
}

I'm usingthe latest Java Mongo driver in Windows 8.1 and using Mongodb 2.4.4. So my question is what is the best method to return a single or multiple qestionEntry element(s) over this entire show collection that match my search string?

Hopefully somebody here can help me with this.

EDIT:

private DB mongoDatabase;
private DBCollection mongoColl;
private DBObject dbObject;

// Singleton class
// Create client (server address(host,port), credential, options)
        mongoClient = new MongoClient(new ServerAddress(host, port), 
                Collections.singletonList(credential),
                options);

mongoDatabase = ClientSingleton.getInstance().getClient().getDB("MyDB");

2.4.4 ?? That's really old version. Please update your mongo to 3.0 if possible. — Jhanvi
– Jhanvi, Commented Jul 23, 2015 at 5:26
@Jhanvi Hi it's a hosted mongodb that we don't have control of the version. Can you help with my query? — TripVoltage
– TripVoltage, Commented Jul 23, 2015 at 7:49

Yathish Manjunath · Accepted Answer · 2015-07-25 12:14:27Z

1

Please try the below :

 db.exp.aggregate([{"$redact":{"$cond": { if: {$gt:[ {"$size": {
 $setIntersection : [ { "$ifNull": [ "$metaTags", []]}, 
 ["House Stark"]]} } , 0 ]} , then:"$$PRUNE",
 else:"$$DESCEND" }}}]).pretty();

[OR]

EDIT :

db.exp.aggregate([{"$unwind":"$show"},
 {"$unwind":"$show.season"},
 {"$unwind":"$show.season.episodes"},
 {"$match" : {"show.season.episodes.questionEntry.metaTags":{"$in": 
   ["Trivia"]}}},
 {"$group":{"_id":"$_id","episodes":{"$push":"$show.season.episodes"}
]);

JAVA CODE :

    MongoClient client = new MongoClient();
    List<String> continentList = Arrays.asList(new String[]{"Trivia"});
    DB db = client.getDB("example");
    DBCollection coll = db.getCollection("exp");
    DBObject matchFields = new 
       BasicDBObject("show.season.episodes.questionEntry.metaTags", 
      new BasicDBObject("$in", continentList));
    DBObject groupFields = new BasicDBObject( "_id",
       "$_id").append("episodes", 
       new BasicDBObject("$push","$show.season.episodes"));
    DBObject unwindshow = new BasicDBObject("$unwind","$show");
    DBObject unwindsea = new BasicDBObject("$unwind", "$show.season");
    DBObject unwindepi = new BasicDBObject("$unwind", 
      "$show.season.episodes");
    DBObject match = new BasicDBObject("$match", matchFields);
    DBObject group = new BasicDBObject("$group", groupFields);      
    AggregationOutput output = 
    coll.aggregate(unwindshow,unwindsea,unwindepi,match,group);

    for (DBObject result : output.results()) {
         System.out.println(result);
         }

edited Jul 25, 2015 at 12:14

answered Jul 23, 2015 at 10:21

Yathish Manjunath

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7 Comments

TripVoltage Over a year ago

thanks for your reply. I'll try that later. Also thanks for answering a previous related post of mine too :-)

TripVoltage Over a year ago

I need to be able to return the whole parent element(s) of any meteTag element that match my search string using Java.

Yathish Manjunath Over a year ago

Please Check i have added few more things in my answer. Hope it resolves your issue :)

TripVoltage Over a year ago

Many thanks, it's working but only for the first item in the metaTags array - well I mean only working for the search string "Season 1" which is the first item? Else it's not entering the loop, also getting a depreciated warning for collection.aggregate so I used @SurpessedWarning("depreciated")..!

Yathish Manjunath Over a year ago

I have executed the code in my machine and it perfectly works fine. If you can see i have used search string "Trivia" which is not the first element in the doucment you have given. I have used the same for testing purpose as well.

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