MongoDB - How to compute field based on other fields existence? - node.js

Question

Suppose I have a trips collection where I would like to compute the status of each trip. The status is calculated based on other fields.
If the trip has no driver it should be pending.
If the trip has a driver it should be in transit.
If the trip has a driver and an invoice number it should be completed.
If the trip has a driver and an invoice number and a bill number it should be billed.
How could I implement this using the aggregation pipeline?
Example docs :
[{
// This has both driver and invoice, should be completed
"_id" : ObjectId("5e24fbfd44621900c5730a48"),
"customer" : ObjectId("5dd7eaf7ef8a7b00ba8f090b"),
"date" : ISODate("2020-01-17T03:00:00.000Z"),
"distance" : 24, // in km
"driver" : ObjectId("5e1e302e26f00000c451923e"),
"invoice" : "0001-00001234",
"status": "completed" // this should be calculated
},
{
// This has only driver, should be in transit
"_id" : ObjectId("5e24fbfd44621900c5730a48"),
"customer" : ObjectId("5dd7eaf7ef8a7b00ba8f090b"),
"date" : ISODate("2020-01-17T03:00:00.000Z"),
"distance" : 24, // in km
"driver" : ObjectId("5e1e302e26f00000c451923e"),
"status": "in transit" // this should be calculated
},
{
// This is missing both driver and invoice, should be pending
"_id" : ObjectId("5e24fbfd44621900c5730a48"),
"customer" : ObjectId("5dd7eaf7ef8a7b00ba8f090b"),
"date" : ISODate("2020-01-17T03:00:00.000Z"),
"distance" : 24, // in km
"status": "pending" // this should be calculated
}]

Answer 1

You can try this, it uses $switch to check all cases in series & $type check for field existence :
db.trips.aggregate([{
$addFields: {
status: {
$switch:
{
branches: [
{
case: { $eq: [{ $type: '$driver' }, 'missing'] },
then: 'pending'
},
{
case: { $eq: [{ $type: '$driver' }, 'objectId'] },
then: 'in transit'
},
{
case: {
$and: [{ $eq: [{ $type: '$driver' }, 'objectId'] },
{ $eq: [{ $type: '$invoice' }, 'string'] }]
},
then: "completed"
},
{
case: {
$and: [{ $eq: [{ $type: '$driver' }, 'objectId'] },
{ $eq: [{ $type: '$invoice' }, 'string'] },
{ $eq: [{ $type: '$billNumber' }, 'string'] }]
},
then: "billed"
}
],
default: '$status'
}
}
}
}
])
Ref : MongoDB-Playground

Answer 2

One solution would be this one:
db.col.updateMany(
{
driver: { $exists: true },
invoice: { $exists: true }
},
{ $set: {status: "completed"}}
)
db.col.updateMany(
{
driver: { $exists: false },
invoice: { $exists: false }
},
{ $set: {status: "pending"}}
)
db.col.updateMany(
{
driver: { $exists: true },
invoice: { $exists: false }
},
{ $set: {status: "in transit"}}
)
Or in a single command witn Aggregation pipeline (Starting in MongoDB 4.2):
db.col.updateMany(
{},
[{
$set: {
status: {
$switch: {
branches: [
{ case: { $and: ["$driver", "$invoice"] }, then: "completed" },
{ case: { $and: ["$driver", { $not: "$invoice" }] }, then: "in transit" },
{ case: { $and: [{ $not: "$driver" }, { $not: "$invoice" }] }, then: "pending" },
],
default: "$status"
}
}
}
}]
)