Querying nested object using $find by applying conditions in Mongodb

Question

This is my json object

{
"account_id" :  "1",
"sections" : [
    "name" : "sec1",
    "label" : {
        "label1" : "text1",
        "label2" : "text2"
        }
    },
    "name" : "sec2",
    "label" : {
        "label3" : "text3",
        "label4" : "text4",
        "label5" : "text5"
         }
    },       
]
}

So in this json I wanted to query the label object where sector= sec1. I have used the below code but it didn't work.

var getData = (db, query) => { 
  return db
    .collection(TABLE_NAME)
    .find(query, { account_id: { sections: { label: 1 } } })
    .toArrayAsync();
};

var dataList = (db, event) => {
  let dataQuery = {
     account_id: id,
     'sections.name': event.params.section
   };
  return getData(db, dataQuery);
};

module.exports.getData = (event, cb) => {
  return using(connectDatabase(), db => {
    return dataList (db, event);
   }).then(data => cb(null, responseObj(data, 200)), err => 
cb(responseObj(err, 500)));
};

Could someone kindly help me? Thanks inadvance.

You Json doesn't seem to be valid. Could you double check it you correctly copy/pasted it? — HamzStramGram
– HamzStramGram, Commented Feb 28, 2019 at 11:45

TRomesh · Accepted Answer · 2019-03-01 10:36:39Z

1

Try something like this. use $project, we can selectively remove or retain field and we can reassign existing field values and derive entirely new values. after projecting the labels and name do a $match to extract the document by name. One thing to notice is that by using $project,it will automatically assign the document's _id.

    var dataList = (db, event) => {
        return db
            .collection(TABLE_NAME)
            .aggregate([ 
              { 
                $match: { account_id: your_id } 
              },
              {
                $unwind: '$sections'
               },
              {
                $project:{labels:'$sections.label',name:'$sections.name'}
              },
               {
               $match:{name:section_name}
             }]).toArray();
          };

edited Mar 1, 2019 at 10:36

answered Mar 1, 2019 at 8:41

TRomesh

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Comments

hoangdv · Accepted Answer · 2019-02-28 13:16:33Z

0

You have to use aggregate method with $unwind syntax to find item in array of object.

var dataList = (db, event) => {
    return db
        .collection(TABLE_NAME)
        .aggregate([
            {
                $match: {
                    account_id: id,
                }
            },
            { $unwind: "$comments" },
            {
                $match: {
                    'name': event.params.section
                }
            }
        ])
        .toArrayAsync();
};

Result:

[{
    "account_id": "1",
    "sections": {
        "name": "sec2",
        "label": {
            "label3": "text3",
            "label4": "text4",
            "label5": "text5"
        }
    }
}]

edited Feb 28, 2019 at 13:16

answered Feb 28, 2019 at 11:47

hoangdv

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3 Comments

Uthpala Pitawela Over a year ago

No it didn't work, the response is a null object . Do I need to do any changes in the .find method

hoangdv Over a year ago

.find(query, { account_id: { sections: { label: 1 } } }) => .find(query)

Uthpala Pitawela Over a year ago

When I changed the code as you have mentioned I got object arrays of both sec1 and sec2. But I wanted the label object which belongs to one particular section. Could you kindly explain how I can do the task?

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