MongoDB: Find all matched array element from single document - arrays

Question

I have a mongodb document like this,
{
"_id" : ObjectId("4e8ae86d08101908e1000001"),
"eId": 101,
"about": "test",
"tags" : [
{"name": "jana"},
{"name":"bala"},
{"name":"jk"},
{"name":"charles"}
]
}
I need to find all matched array elements, where the name matched with given array.
db.coll.find({"tags": {"$elemMatch": {"name": {"$in": [/^jana/i, /^charles/i] }}}})
for this query i got the following result
{
"_id" : ObjectId("4e8ae86d08101908e1000001"),
"tags" : [
{
"name" : "jana"
}
]
}
$elemMatch query only return the first matched element, but i want all the matched array element like this,
{
"_id" : ObjectId("4e8ae86d08101908e1000001"),
"tags" : [
{
"name" : "jana"
},
{
"name" : "charles"
}
]
}
Is it possible to get the result like this?
note: i don't want any others fields, I want only the matched array elements along with _id

Answer 1

You can use MongoDB Aggregation Pipeline:
db.coll.aggregate([
{'$unwind': '$tags'},
{'$match':
{"tags.name":
{"$in": [/^jana/, /^charles/i] }
}
},
{'$group':
{
'_id': '$_id',
'tags':
{'$push': '$tags'}
}
}
])
Result : -
{
"result" : [
{
"_id" : ObjectId("5538b214706a90c718f75a41"),
"tags" : [
{
"name" : "jana"
},
{
"name" : "charles"
}
]
}
],
"ok" : 1
}