MongoDB: query nested array by more than one condition - mongodb

Question

Say this is one item from my users collection:
{
"_id" : "5545f4c4d0dd52c355a99fbe",
"name" : "Dollie James",
"device" : "iOS",
"gender" : "Female",
"wallet" : [
{
"store" : "All Saints",
"balance" : "$196.11",
"date" : "2014-02-22T22:09:38 -10:00",
"tags" : [
"Tshirt",
"Summer"
]
},
{
"store" : "Nike",
"balance" : "$367.76",
"date" : "2014-04-18T14:44:30 -10:00",
"tags" : [
"Shoes"
]
}
]
}
This record was returned from the following query:
db.users.findOne({$and:[{"wallet.tags" : "Tshirt"}, {"wallet.store":"Nike"}]})
However this is not the result I want because Tshirt and Nike are not in the same object in the wallet array. It seems that mongo is doing a query on the entire array. How can I target this query to only return my two conditions that are in the same object within the array?

Answer 1

You don't need $and (as it will apply conditions independently) but $elemMatch. From the doc:
The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria.
In your specific case:
> db.wallet.find(
{wallet: { $elemMatch:{"tags" : "Tshirt", "store":"Nike"}}}
).pretty()
{
"_id" : "5545f4c4d0dd52c355a99f00",
"name" : "Working example",
"device" : "iOS",
"gender" : "Female",
"wallet" : [
{
"store" : "Nike",
"balance" : "$196.11",
"date" : "2014-02-22T22:09:38 -10:00",
"tags" : [
"Tshirt",
"Summer"
]
}
]
}