Get Days Between 2 MongoDB ISODates [duplicate] - mongodb

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Closed 3 years ago.
I am trying to get the days difference between 2 ISODates and put it in days field. I have these documents below:
{
created_at: ISODate("2019-06-06TT00:00:00Z"),
completed_at: "2019-06-08"
},
{
created_at: ISODate("2019-06-06TT00:00:00Z"),
completed_at: null
},
{
created_at: ISODate("2019-06-06TT00:00:00Z"),
completed_at: "2019-06-04"
}
What I have tried so far is to get the milliseconds. But I don't want that. I just want to substract the dates and get the difference in days.
db.collection.aggregate([
{
$addFields: {
completed_at: {
$ifNull: [
{
"$dateFromString": {
"dateString": "$completed_at"
}
},
new ISODate()
]
}
}
},
{
$addFields: {
days: {
$cond: [
{"$lte": ["$completed_at", "$created_at"]},
0,
{
$divide: [
{
$subtract: [
"$completed_at",
"$created_at"
]
},
86400000
]
}
]
}
}
},
{
$project: {
_id: 0,
created_at: 1,
completed_at: 1,
days: 1
}
}
])
If completed_at field is null, then the value for this should be the current date. If completed_at is lesser than created_at, then days is 0. Let's say current date is June 6, 2019, desired result should be:
{
days: 2
},
{
days: 0
},
{
days: 0
}

Answer 1

I think I was able to get it. I removed the time in the date fields and the results that I wanted is showing correctly. Please let me know if I got it correctly or there are some adjustments that I need to make in order to make it faster. Thank you!
db.collection.aggregate([
{
$addFields: {
created_at: {
$dateFromParts: {
"year": {
$year: "$created_at"
},
"month": {
$month: "$created_at"
},
"day": {
$dayOfMonth: "$created_at"
}
}
},
completed_at: {
$ifNull: [
{
"$dateFromString": {
"dateString": "$completed_at"
}
},
{
$dateFromParts: {
"year": {
$year: new Date()
},
"month": {
$month: new Date()
},
"day": {
$dayOfMonth: new Date()
}
}
}
]
}
}
},
{
$addFields: {
days: {
$cond: [
{
"$lte": [
"$completed_at",
"$created_at"
]
},
0,
{
$divide: [
{
$subtract: [
"$completed_at",
"$created_at"
]
},
86400000
]
}
]
}
}
},
{
$project: {
_id: 0,
created_at: 1,
completed_at: 1,
days: 1
}
}
])