Using top in mongodb aggregation
As mongo docs says:
MongoDB aggregation stage limits
Each stage can use up to 100 MB of RAM. You will get an error from the database if you exceed this limit. So if you are having this problem and you need the first (or last) element from a sorted collection, you can use the top operator.
So instead of sorting:
db.Entity.aggregate([
{
"$match": {
"startTime": {
"$gte": ISODate("2025-04-02T22:00:00Z"),
"$lt": ISODate("2025-04-03T22:00:00Z")
}
}
},
{
"$addFields": {
"creatorPriority": {
"$switch": {
"branches": [
{ "case": { "$eq": ["$creator", "ADMIN"] }, "then": 1 }
],
"default": 0
}
}
}
},
{
"$sort": {
"creatorPriority": -1,
"createdAt": -1
}
},
{
"$group": {
"_id": {
"deviceId": "$deviceId",
"startTime": "$startTime"
},
"records": { "$push": "$$CURRENT" }
}
},
{
"$replaceRoot": {
"newRoot": { "$first": "$records" }
}
}
])
Use top:
db.Entity.aggregate([
{
"$match": {
"startTime": {
"$gte": ISODate("2025-06-18T22:00:00Z"),
"$lt": ISODate("2025-06-20T22:00:00Z")
}
}
},
{
"$addFields": {
"creatorPriority": {
"$switch": {
"branches": [
{ "case": { "$eq": ["$creator", "ADMIN"] }, "then": 1 }
],
"default": 0
}
}
}
},
{
"$group": {
"_id": {
"entityId": "$entityId",
"startTime": "$startTime"
},
"topRecord": {
"$top": {
"sortBy": { "createdAt": -1 },
"output": "$$ROOT"
}
}
}
},
{
"$replaceRoot": {
"newRoot": "$topRecord"
}
}
] , {
allowDiskUse: false
})