Suppose I have this MongoDB document:
{
"_id": {
"$oid": "628f739398580cae9c21b44f"
},
"place":"Amsterdam",
"events": [
{
"eventName": "Event one",
"eventText": "Event",
"eventDate": "010101"
"host":"Bob"
},
{
"eventName": "E2",
"eventText": "e2",
"eventDate": "020202"
"host":"John"
}
]
}
{
"_id": {
"$oid": "628f739398580cae9c21b44f"
},
"place":"London",
"events": [
{
"eventName": "e3",
"eventText": "e3",
"eventDate": "010101",
"host":"Bob"
}
]
}
And I want to get the array block of events being hosted by Bob, how would I do that? I have tried to use $elemSelector like this:
const result = await mongoDatabase
.collection("temp")
.find({ events: { $elemMatch: { eventName: "E2" } } })
.toArray();
console.log(JSON.stringify({ result }));
But it just returns all events at the same place as the selected, Amsterdam in this case.
Wanted result:
{
"eventName": "Event one",
"eventText": "Event",
"eventDate": "010101"
"host":"Bob"
},
{
"eventName": "e3",
"eventText": "e3",
"eventDate": "010101",
"host":"Bob"
}
Check this out
db.collection.aggregate({
$unwind: "$events"
},
{
$match: {
"events.host": "Bob"
}
},
{
"$project": {
"events": 1,
"_id": 0
}
},
{
"$replaceRoot": {
"newRoot": "$events"
}
})
And you can play around with more test data here: https://mongoplayground.net/p/A1UbZdZgZmr
You can achieve with simple pipeline stages
db.collection.aggregate([
{
"$match": {//Match
"events.host": "Bob"
}
},
{
"$project": {
"e": {
"$filter": {//Filter matching elements
"input": "$events",
"as": "event",
"cond": {
"$eq": [
"$$event.host",
"Bob"
]
}
}
}
}
}
])
Following Structure can be achieved by using projection query in MongoDB one lucid solution for the above can be this
db.collection("temp").find({ "events":{ $elemMatch:{ "eventName":"e3" } } }, {"events":1,"_id":0})