Mongodb Search with embedded document. - mongodb

Question

Structure of mongodb collection is like this.
collection User
{
"name":"sufaid",
"age":"22",
"address":"zzzz",
"product":[{"id":1,"name":"A"},
{"id":6,"name":"N"},
{"id":3,"name":"D"},
{"id":7,"name":"q"},
]
}
I need to find users those who have product id "3"
Out put should be like this
{
"name":"sufaid",
"age":"22",
"address":"zzzz",
"product":{"id":3,"name":"D"}
}
Note : With out using $unwind and projection like "product.$"
"product.$" through error while using pymongo.
Any other option is there ???

Answer 1

use $elemMatch. https://docs.mongodb.com/manual/reference/operator/projection/elemMatch/
for your query:
db.User.find({},{name:1,age:1,address:1,product:{$elemMatch:{id:3}}})
or
db.User.find({},{product:{$elemMatch:{id:3}}})
o/p: {
"name" : "sufaid",
"age" : "22",
"address" : "zzzz",
"product" : [
{
"id" : 3.0,
"name" : "D"
}
]
}
As you require it for aggregation:
db.User.aggregate([
{$unwind:'$product'},
{$match:{'product.id':3}},
{$project:{_id:0,name:1,age:1,aaddress:1,product:1}}
])
o/p:
{
"name" : "sufaid",
"age" : "22",
"address" : "zzzz",
"product" : {
"id" : 3.0,
"name" : "D"
}
}
This will give exactly what you indicated in the question.

Answer 2

You could use the aggregation framework which has a plethora of operators that you can use, in particular you'd need the $filter and $arrayElemAt operators in a $project pipeline.
For instance, you could return just the product field as an embedded document by running the following pipeline:
db.user.aggregate([
{ "$match": { "product.id": 3 } },
{
"$project": {
"name": 1,
"age": 1,
"address": 1,
"product": {
"$arrayElemAt": [
{
"$filter": {
"input": "$product",
"as": "item",
"cond": { "$eq": [ "$$item.id", 3 ] }
}
},
0
]
}
}
}
])
Sample Output
{
"_id" : ObjectId("5829ac89628123dcf8a64b7a"),
"name" : "sufaid",
"age" : "22",
"address" : "zzzz",
"product" : {
"id" : 3,
"name" : "D"
}
}
If you just need an output with the array filtered, skip the $arrayElemAt expression and use the $filter only:
db.user.aggregate([
{ "$match": { "product.id": 3 } },
{
"$project": {
"name": 1,
"age": 1,
"address": 1,
"product": {
"$filter": {
"input": "$product",
"as": "item",
"cond": { "$eq": [ "$$item.id", 3 ] }
}
}
}
}
])
Sample Output
{
"_id" : ObjectId("5829ac89628123dcf8a64b7a"),
"name" : "sufaid",
"age" : "22",
"address" : "zzzz",
"product" : [
{ "id" : 3, "name" : "D" }
]
}

Answer 3

db.User.find({},{product:{$elemMatch:{id:3}}})
it's enough