Using $in but matching on specific fields - mongodb

Question

I'm attempting to use $in to query a mongoDB collection. The issue I'm running up against is that the arrays are arrays of JSON objects, not just arrays of a single field. So the full object looks like this:
{
items: [
{
name: "Jacket",
other_field: "1234"
}
]
}
So if I have an array that looks like this:
[{name:"Jacket", other_field:"3456"}]
I'd like to query for documents that contain within their items array any object which has a matching name field, ignoring all other fields. Is that possible?

Answer 1

You can use $elemMatch for this.
Example -
db.users.find({items: { $elemMatch: {name:'Jacket'} } } )
For more understanding, you can refer to - $elemMatch

Answer 2

As per your question there should be two possibilities if your documents structure looks like below
{
items: [
{
name: "Jacket",
other_field: "1234"
}
]
}
In this case you use following query
db.collectionName.find({"items.name":"Jacket"},{"items":1})
so above query will return only matching items.name matching criteria.
And another more possibilities if your documents structure looks like nested as below
{
items: [
{
name: "Jacket",
other_field: "1234"
},
{
name: "Jacket",
other_field: "12345"
},
{
name: "Jacket2",
other_field: "1234e"
}
]
}
In this case should use aggregate function as below
db.collectionName.aggregate({
"$unwind": "$items"
},
{
"$match": {
"items.name": "Jacket"
}
},
{
"$project": {
"_id": 0,
"items.name": 1,
"items.other_field": 1
}
})

Answer 3

if I understood your requirement correctly then could could ask
db.collectionName.find({'items.name': 'Jacket'})
MongoDB automatically does the "descending down" into the arrays and pick the ones that match.
fricke