I have 3 documents:
{
"id": 1,
"user": "Brian1",
"configs": [
"a",
"b",
"c",
"d"
]
}
----
{
"id": 2,
"user": "max_en",
"configs": [
"a",
"h",
"i",
"j"
]
}
----
----
{
"id": 3,
"user": "userX",
"configs": [
"t",
"u",
"s",
"b"
]
}
I want to merge all the "configs" arrays into one array without dublicates,like this:
{
"configs": [
"a",
"b",
"c",
"d",
"h",
"i",
"j",
"t",
"u",
"s",
]
}
I've tried the following:
Aggregation.group("").addToSet("configs").as("configs") and { _id: "", 'configs': { $addToSet: '$configs' } }
The first one gives an error because I've left the fieldname empty (I don't know what to put there).
The second one returns a merged array but with duplicates.
When you want to group all the documents, you need to add {_id: null}
It means group all documents.
Probably you need this
db.collection.aggregate([
{
"$unwind": "$configs"
},
{
$group: {
_id: null,
configs: {
"$addToSet": "$configs"
}
}
}
])
But be cautious when you need to use on larger collection without a match.