How can I compare two string format times? - mongodb

Question

I have a collection called "project" which is having a field expected time and actual time both are in string format
{
"_id" : ObjectId("5ce7455d77af2d1143f84d49"),
"project_name" : "p1",
"expected" : "0:11:30",
"actual" : "7:30:00",
}
How can I compare two string format times using mongodb?
I want to find if actual time is more than expected

Answer 1

You can use $split with $toInt (MongoDB 4.0 or newer) to convert your string values to a number of seconds and then use $expr to compare both fields:
db.col.aggregate([
{
$addFields: {
expected: {
$let: {
vars: {
parts: {
$split: [ "$expected", ":" ]
}
},
in: {
$sum: [
{ $toInt: { $arrayElemAt: [ "$$parts", 2 ] } },
{ $multiply: [ 60, { $toInt: { $arrayElemAt: [ "$$parts", 1 ] } } ] },
{ $multiply: [ 3600, { $toInt: { $arrayElemAt: [ "$$parts", 0 ] } } ] }
]
}
}
},
actual: {
$let: {
vars: {
parts: {
$split: [ "$actual", ":" ]
}
},
in: {
$sum: [
{ $toInt: { $arrayElemAt: [ "$$parts", 2 ] } },
{ $multiply: [ 60, { $toInt: { $arrayElemAt: [ "$$parts", 1 ] } } ] },
{ $multiply: [ 3600, { $toInt: { $arrayElemAt: [ "$$parts", 0 ] } } ] }
]
}
}
}
}
},
{
$match: {
$expr: { $gt: [ "$expected", "$actual" ] }
}
}
])

Answer 2

You can convert time to any date you want using $dateFromString operator and then can easily use $lte $gte to perform simple match operations.
db.collection.find({
"$expr": {
"$gt": [
{ "$dateFromString": {
"dateString": {
"$concat": ["2018-09-19", "T", "$actual"]
}
}},
{ "$dateFromString": {
"dateString": {
"$concat": ["2018-09-19", "T", "$expected"]
}
}}
]
}
})