Sort a match group by id in aggregate - mongodb

Question

(Mongo newbie here, sorry) I have a mongodb collection, result of a mapreduce with this schema :
{
"_id" : "John Snow",
"value" : {
"countTot" : 500,
"countCall" : 30,
"comment" : [
{
"text" : "this is a text",
"date" : 2016-11-17 00:00:00.000Z,
"type" : "call"
},
{
"text" : "this is a text",
"date" : 2016-11-12 00:00:00.000Z,
"type" : "visit"
},
...
]
}
}
My goal is to have a document containing all the comments of a certain type. For example, a document John snow with all the calls.
I manage to have all the comments for a certain type using this :
db.general_stats.aggregate(
{ $unwind: '$value.comment' },
{ $match: {
'value.comment.type': 'call'
}}
)
However, I can't find a way to group the data received by the ID (for example john snow) even using the $group property. Any idea ?
Thanks for reading.

Answer 1

Here is the solution for your query.
db.getCollection('calls').aggregate([
{ $unwind: '$value.comment' },
{ $match: {
'value.comment.type': 'call'
}},
{
$group : {
_id : "$_id",
comment : { $push : "$value.comment"},
countTot : {$first : "$value.countTot"},
countCall : {$first : "$value.countCall"},
}
},
{
$project : {
_id : 1,
value : {"countTot":"$countTot","countCall":"$countCall","comment":"$comment"}
}
}
])
or either you can go with $project with $filter option
db.getCollection('calls').aggregate([
{
$project: {
"value.comment": {
$filter: {
input: "$value.comment",
as: "comment",
cond: { $eq: [ "$$comment.type", 'call' ] }
}
},
"value.countTot":"$value.countTot",
"value.countCall":"$value.countCall",
}
}
])
In both case below is my output.
{
"_id" : "John Snow",
"value" : {
"countTot" : 500,
"countCall" : 30,
"comment" : [
{
"text" : "this is a text",
"date" : "2016-11-17 00:00:00.000Z",
"type" : "call"
},
{
"text" : "this is a text 2",
"date" : "2016-11-17 00:00:00.000Z",
"type" : "call"
}
]
}
}

Answer 2

Here is the query which is the extension of the one present in OP.
db.general_stats.aggregate(
{ $unwind: '$value.comment' },
{ $match: {
'value.comment.type': 'call'
}},
{$group : {_id : "$_id", allValues : {"$push" : "$$ROOT"}}},
{$project : {"allValues" : 1, _id : 0} },
{$unwind : "$allValues" }
);
Output:-
{
"allValues" : {
"_id" : "John Snow",
"value" : {
"countTot" : 500,
"countCall" : 30,
"comment" : {
"text" : "this is a text",
"date" : ISODate("2016-11-25T10:46:49.258Z"),
"type" : "call"
}
}
}
}

Answer 3

Got my answer looking at this :
How to retrieve all matching elements present inside array in Mongo DB?
using the $addToSet property in the $group one.