How to fetch nested object based on key value using mongodb?

Question

I have a record of following format...

{
"_id" : ObjectId("609cd99d1af4ac1036d78f7d"),
"userrole" : "admins",
"locks" : [
{
"userid" : "2932fb99-4c41-4342-99e0-af15f8146da0",
"useremail" : "fsasdev@gmail.com",
"filepath" : "output/notes.txt",
.
.
}
]
}

How to fetch userid,useremail where filepath matches"output/notes.txt"?

Tushar Gupta - curioustushar · Accepted Answer · 2021-05-13T08:43:05.967

1

Demo - https://mongoplayground.net/p/FFYYCqOmPx-

Use $

The positional $ operator limits the contents of a to return the first element that matches the query condition on the array.

db.collection.find({
  "locks.filepath": "output/notes.txt" // query 
},
{
  "locks.$": 1 // projection
})

Demo - https://mongoplayground.net/p/TLqmuhN6H3q

db.collection.aggregate([
  {
    $match: { "locks.filepath": "output/notes.txt" } // filter to reduce load in unwind
  },
  { $unwind: "$locks" }, //  break into individual documents
  {
    $match: { "locks.filepath": "output/notes.txt" } // filter
  },
  {
    $replaceRoot: { "newRoot": "$locks" } // set root as $locks
  }
])

edited May 13 '21 at 08:43

answered May 13 '21 at 08:37

Tushar Gupta - curioustushar

54,013
22
95
103

I want to fetch only details of that particular object , how can i achieve that? – s d May 13 '21 at 08:41
@sd updated answer – Tushar Gupta - curioustushar May 13 '21 at 08:44
This works very well, Thank you so much for the quick answer. can you also please tell me why you have used $match twice? it works if i use it only once – s d May 13 '21 at 08:59
1

with huge dataset unwind will run all documents, we want to reduce that to make query faster, so we are filtering records 1st to make sure we get fewer records for unwinding. – Tushar Gupta - curioustushar May 13 '21 at 09:01

How to fetch nested object based on key value using mongodb?

1 Answers1