Let's say I have a collection of objects:
{
_id : 1,
list1 : [
{ name: 'This is my name', value: 'This is my value' },
{ name: 'name number 2', value: 'value number 2' }
],
list2 : [
{ name: 'Another name', value: 'Another value' }
],
deeper : {
list3 : [
{ name: 'Another name but even deeper', value: 'Another value but deeper' }
]
}
}
Using aggregation pipeline how would I return a single list of name/value objects? Result should be:
{
_id : 1,
combinedList : [
{ name: 'This is my name', value: 'This is my value' },
{ name: 'name number 2', value: 'value number 2' },
{ name: 'Another name', value: 'Another value' },
{ name: 'Another name but even deeper', value: 'Another value but deeper' }
]
}
PART 2:
Now, how to flatten deeply nested objects from a whole collection into a single response? Example:
{
"_id" : 0,
list1 : [
{ name: 'This is my name', value: 'This is my value' },
{ name: 'name number 2', value: 'value number 2' }
],
list2 : [
{ name: 'Another name', value: 'Another value' }
]
},
{
"_id" : 1,
list1 : [
{ name: 'This is my name', value: 'This is my value' },
{ name: 'name number 2', value: 'value number 2' }
],
deeper : {
list2 : [
{ name: 'Another name but even deeper', value: 'Another value but deeper' }
]
}
}
The result should be the same document as above (combinedList).
you can use aggregate
and setUnion
db.coll.aggregate([
{
$match:{_id:1}
},
{
$project: {_id: 0 ,
combinedList: { $setUnion: [ "$deeper.list3","$list2", "$list1" ] }}
}
]
)
result
{
"result" : [
{
"combinedList" : [
{
"name" : "Another name but even deeper",
"value" : "Another value but deeper"
},
{
"name" : "Another name",
"value" : "Another value"
},
{
"name" : "name number 2",
"value" : "value number 2"
},
{
"name" : "This is my name",
"value" : "This is my value"
}
]
}
],
"ok" : 1
}
http://docs.mongodb.org/manual/reference/operator/aggregation/setUnion/
you have to use version 2.6.
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