I have the following mongodb collection
{ "id" : "yzes547",
"courseId" : "aw4a34y7",
"objectives" : [
{
"type" : "LESSON",
"id" : "dfhxytd"
},
{
"type" : "MODULE",
"id" : "rgzeerp"
}
]
}
I want to add new fields for ids of each type in objectives parameter.
Desired output
{ "id" : "yzes547",
"courseId" : "aw4a34y7",
"objectives" : [
{
"type" : "LESSON",
"id" : "dfhxytd"
},
{
"type" : "MODULE",
"id" : "rgzeerp"
}
]
"lessonId": "dfhxytd",
"moduleId": "rgzeerp"
}
I have tried the following query but it only returns False.
db.account.aggregate([
{
'$project': {
'_id': 0,
'questionId': 1,
'courseId': 1,
'lessonId': {
'$cond': [
{
'$eq': [
'$objectives.type', 'LESSON'
]
}, '$objectives.id', False
]
},
'moduleId': {
'$cond': [
{
'$eq': [
'$objectives.type', 'MODULE'
]
}, '$objectives.id', False
]
}
Is it possible to query the database such that we can get new fields of each type in one aggregation method?
Yes, you can achieve this quite easily using $map and $objectToArray to create the required fields, finally by using $replaceRoot and $mergeObjects you can add these fields to the original structure, like so:
db.collection.aggregate([
{
$replaceRoot: {
newRoot: {
"$mergeObjects": [
"$$ROOT",
{
"$arrayToObject": {
$map: {
input: "$objectives",
as: "obj",
in: {
k: {
$concat: [
{
"$toLower": "$$obj.type"
},
"Id"
]
},
v: "$$obj.id"
}
}
}
}
]
}
}
}
])