How to retrieve data from the previous day without explicitly specifying a date?

Working with Studio 3T IntelliShell
1

Hi everyone!

I’m trying to create a query that gets the data from the previous day for automatization purposes. I’m writing this:

db.getCollection(“media”).aggregate([
{
“$addFields”: {
“today”: {
“$dateFromString”: {
“dateString”: {
“$dateToString”: {
“date”: “$$NOW”,
“format”: “%Y-%m-%dT%H:%M:%S%z”
}
}
}
}
}
},
{
“$addFields”: {
“yesterday”: {
“$dateFromString”: {
“dateString”: {
“$dateToString”: {
“date”: {
“$subtract”: [
“$$NOW”,
86400000 // Milliseconds in a day
]
},
“format”: “%Y-%m-%dT%H:%M:%S%z”
}
}
}
}
}
},
{
“$match”: {
“dateAdded”: {
“$gte”: “$yesterday”,
“$lt”: “$today”
}
}
},
{
“$project”: {
“today”: 0,
“yesterday”: 0
}
}
])

However, I’m getting this error: Mongo Server error (MongoCommandException): Command failed with error 17276 (Location17276): ‘Use of undefined variable: NOW’ on server 20.114.50.151:27017.

The full response is:
{
“ok” : 0.0,
“errmsg” : “Use of undefined variable: NOW”,
“code” : 17276.0,
“codeName” : “Location17276”
}

It seems like my free version of Studio 3T does not support the “NOW” function. Does anybody have any idea how to achieve this?

2

Hey there! Sorry for the late reply on this!

I’ve just tried replicating the issue but your query runs fine on my MongoDB server. The $$NOW variable should be evaluated entirely by the server, Studio 3T doesn’t parse it at all.

Are you running a version older than 4.2? The $$NOW variable was only added in MongoDB 4.2: https://www.mongodb.com/docs/manual/reference/aggregation-variables/#mongodb-variable-variable.NOW

1 Like