Project embedded document key value, based on condition in mongoDB aggregation - mongodb

Question

I have a mongo collection called tickets and we are storing ticket details in similar structure documents like this:
[
{
"status": "PAUSED",
"lifecycle_dates": {
"OPEN": "d1",
"CLOSED": "d2",
"PAUSED": "d3"
}
},
{
"status": "OPEN",
"lifecycle_dates": {
"OPEN": "d1",
"PAUSED": "d3"
}
},
{
"status": "CLOSED",
"lifecycle_dates": {
"OPEN": "d1",
"CLOSED": "d2"
}
}
]
I need to fetch the data which says current status of ticket and status date on.
and I want to project data like :
[
{
"status": "PAUSED",
"lifecycle_date": "d3"
},
{
"status": "OPEN",
"lifecycle_date": "d1"
},
{
"status": "CLOSED",
"lifecycle_date": "d2"
}
]
How can I project single lifecycle date based on current status in mongo aggregation pipeline?
something like this:
{
$project : {
"status" : 1,
"lifecycle_date" : $lifecycle_dates[$status]
}
}
couldn't find any reference or similar problem in mongo reference document here
current mongo version : 3.2

Answer 1

Updated Answer :
Since you need to fetch the date as per the status, you can use this aggregate query :
db.test.aggregate([
{
$project : {
_id : 0,
status : 1,
lifecycle_date : { $cond: [ {$eq : ["$status","OPEN"]}, "$lifecycle_dates.OPEN", { $cond: [ {$eq : ["$status","CLOSED"]}, "$lifecycle_dates.CLOSED", { $cond: [ {$eq : ["$status","PAUSED"]}, "$lifecycle_dates.PAUSED", "-1" ]} ]} ]}
}
}])
This is compatible with Mongo 3.2 as well.
Output :
{ "status" : "PAUSED", "lifecycle_date" : "d3" }
{ "status" : "OPEN", "lifecycle_date" : "d1" }
{ "status" : "CLOSED", "lifecycle_date" : "d2" }
=========================================================================
This answer was for the previous question -
Use this aggregate :
db.test.aggregate([
{
$project : {
_id : 0,
status : 1,
lifecycle_date : "$lifecycle_dates.PAUSED"
}
}
])
Output :
{ "status" : "PAUSED", "lifecycle_date" : "d3" }

Answer 2

You can try below aggregation
db.collection.aggregate([
{ "$project": {
"status": 1,
"lifecycle_date": {
"$arrayElemAt": [
{ "$filter": {
"input": { "$objectToArray": "$lifecycle_dates" },
"as": "life",
"cond": { "$eq": ["$$life.k", "$status"] }
}},
0
]
}
}},
{ "$project": {
"status": 1,
"lifecycle_date": "$lifecycle_date.v"
}}
])

Answer 3

db.tickets.aggregate(
// Pipeline
[
// Stage 1
{
$project: {
"status": 1,
_id: 0,
"lifecycle_dates": {
$switch: {
branches: [{
case: {
$eq: ["$status", "PAUSED"]
},
then: "$lifecycle_dates.PAUSED"
},
{
case: {
$eq: ["$status", "OPEN"]
},
then: "$lifecycle_dates.OPEN"
},
{
case: {
$eq: ["$status", "CLOSED"]
},
then: "$lifecycle_dates.OPEN"
}
],
}
}
}
},
])