monogdb nested array items exact match - mongodb

Question

I have a collection as below what I want is to fetch the items that has exact match of Tag="dolore", I tried different ways but I am getting all the elements if any of the embedded element has tag as dolore
{
"_id" : 123,
"vendor" : "ut",
"boxes" : [
{
"boxRef" : 321,
"items" : [
{
"Tag" : "dolore",
},
{
"Tag" : "irure",
},
{
"Tag" : "labore",
}
]
},
{
"boxRef" : 789,
"items" : [
{
"Tag" : "incididunt",
},
{
"Tag" : "magna",
},
{
"Tag" : "laboris",
}
]
},
{
"boxRef" : 456,
"items" : [
{
"Tag" : "reprehenderit",
},
{
"Tag" : "reprehenderit",
},
{
"Tag" : "enim",
}
]
}
]
}

Answer 1

If you are expecting to get only the matching embedded documents you have $unwind, $match and then $group to reverse the $unwind. Like this:
db.getCollection('collectionName').aggregate([
{
$unwind:"$boxes"
},
{
$unwind:"$boxes.items"
},
{
$match:{
"boxes.items.Tag":"dolore"
}
},
{
$group:{
_id:{
boxRef:"$boxes.boxRef",
_id:"$_id"
},
vendor:{
"$first":"$vendor"
},
boxRef:{
"$first":"$boxes.boxRef"
},
items:{
$push:"$boxes.items"
}
}
},
{
$group:{
_id:"$_id._id",
vendor:{
"$first":"$vendor"
},
boxes:{
$push:{
boxRef:"$boxRef",
items:"$items"
}
}
}
},
])
Output:
{
"_id" : 123.0,
"vendor" : "ut",
"boxes" : [
{
"boxRef" : 321.0,
"items" : [
{
"Tag" : "dolore"
}
]
}
]
}