How can I concat two elements of splitted fields from mongodb collections?

Question

I have github repos URLs in a mongodb collection. (comments)

url: "https://api.github.com/repos/andymckay/solitude/comments/1573261" 

I want to split this field according to slash (/) delimiter. After this process, I have array likes below.

https:, , api.github.com, repos, andymckay, solitude, .comments, 1573261

Than I want to concat 4. and 5. elements of array with slash operator; Finally I want to obtain a field like this;

full_name :"andymckay/solitude"

I am newby about mongodb, I solve this with this query;

db.getCollection("commentsURL").aggregate([
       {$project: 
          {
             _id:1,
             url2:{$arrayElemAt:[{$split:["$url", "/"]}, 4]},
             url3:{$arrayElemAt:[{$split:["$url", "/"]}, 5]}
          }
       },
       { $addFields: { full_name: { $concat: [ "$url2", "/", "$url3" ] } } },      
       {$out:"comments2"}
     ]);

Results of this query, It creates the collection below;

{ 
    "_id" : ObjectId("5266780cbd35436070000001"), 
    "url2" : "andymckay", 
    "url3" : "solitude", 
    "full_name" : "andymckay/solitude"
}

Is there any method easier than mine?

Answer 1

db.getCollection("commentsURL").aggregate([
       {$project: 
          {
             _id:1,
             url2:{$arrayElemAt:[{$split:["$url", "/"]}, 4]},
             url3:{$arrayElemAt:[{$split:["$url", "/"]}, 5]}
          }
       },
       { $addFields: { full_name: { $concat: [ "$url2", "/", "$url3" ] } } },      
       {$out:"comments2"}
     ]);

After that a projection query, I can get full_name of repos;

db.getCollection("comments").find({},{"_id":1,"full_name":1}).forEach(function(doc){
db.comments2.insert(doc);});