I have documents like:
{
"platform":"android",
"install_date":20151029
}
- platform - can have one value from [android|ios|kindle|facebook ] .
- install_date - there are many install_dates
There are also many fields.
Aim : I am calculating installs per platform on particular date.
So I am using group by in aggregation framework and make counts by platform. Document should look like like:
{
"install_date":20151029,
"platform" : {
"android":1000,
"ios": 2000,
"facebook":1500
}
}
I have done like:
db.collection.aggregate([
{
$group: {
_id: { platform: "$platform",install_date:"$install_date"},
count: { "$sum": 1 }
}
},
{
$group: {
_id: { install_date:"$_id.install_date"},
platform: { $push : {platform :"$_id.platform", count:"$count" } }
}
},
{
$project : { _id: 0, install_date: "$_id.install_date", platform: 1 }
}
])
which Gives document like:
{
"platform": [
{
"platform": "facebook",
"count": 1500
},
{
"platform": "ios",
"count": 2000
},
{
"platform": "android",
"count": 1000
}
],
"install_date": 20151027
}
Problem:
Projecting array to single object as "platform"
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