want to convert "00:10:00" to a single integer in mongodb - mongodb

Question

There are many documents in the collection which contains this field timeTaken: "00:10:00",
I want to sum up from all the documents and have to give a single integer in mongodb robo3T.
That is for the following documents:
[
{ timeTaken: "00:10:00" },
{ timeTaken: "01:10:00" },
{ timeTaken: "02:20:50" }
]
I want the result to be:
{ timeTaken: "03:40:50" }

Answer 1

Our strategy will be to split the string into minutes, seconds and hours, convert them to numbers, sum them up and then reconstruct the structure.
For this you will need access to operators like $toString and $toInt which means you can only do this for version 4.0+, for older Mongo versions you will have to read the documents and do this in code.
I've split the following query into multiple stages so it's clearer what I'm doing but this could be re-written into just 2 stages, the $group stage and a final $project stage to restructure the data.
db.collection.aggregate([
{
"$addFields": {
dataParts: {
$map: {
input: {
$split: [
"$data",
":"
]
},
as: "num",
in: {
"$toInt": "$$num"
}
}
},
}
},
{
$group: {
_id: null,
seconds: {
$sum: {
"$arrayElemAt": [
"$dataParts",
2
]
}
},
minutes: {
$sum: {
"$arrayElemAt": [
"$dataParts",
1
]
}
},
hours: {
$sum: {
"$arrayElemAt": [
"$dataParts",
0
]
}
},
}
},
{
"$addFields": {
finalSeconds: {
$mod: [
"$seconds",
60
]
},
}
},
{
$addFields: {
minutes: {
$sum: [
"$minutes",
{
"$divide": [
{
"$subtract": [
"$seconds",
"$finalSeconds"
]
},
60
]
}
]
},
}
},
{
$addFields: {
finalMinutes: {
$mod: [
"$minutes",
60
]
},
finalHours: {
$sum: [
"$hours",
{
$mod: [
{
$max: [
{
"$subtract": [
"$minutes",
60
]
},
0
]
},
60
]
}
]
}
}
},
{
$project: {
final: {
$concat: [
{
"$toString": "$finalHours"
},
":",
{
"$toString": "$finalMinutes"
},
":",
{
"$toString": "$finalSeconds"
},
]
}
}
}
])
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