How to preserve a UNIX datestamp with mongodb aggregation - mongodb

Question

I would like to aggregate data in meteor/MongoDB. I have a few thousand entries formatted like the following
{_id: sadsadjhsjdys7ad67as8d, t: 1464162907, prod: 123, sys: xyz}
I would like to sort them into their relative dates and aggregate the prod field.
I currently have the following
var project = {
"$project" : {
"_id" : 0,
"y" : {
"$year" : {
"$add" : [
new Date(0), {
"$multiply" : [1000, "$t"]
}
]
}
},
"m" : {
"$month" : {
"$add" : [
new Date(0), {
"$multiply" : [1000, "$t"]
}
]
}
},
"d" : {
"$dayOfMonth" : {
"$add" : [
new Date(0), {
"$multiply" : [1000, "$t"]
}
]
}
},
"prod" : "$prod",
"sys" : "$sys"
}
};
var group = {
"$group" : {
"_id" : {
"year" : "$y",
"month" : "$m",
"day" : "$d",
"test" : "$test"
},
sys : "sys",
prod : {
$sum : "$prod"
}
}
};
var result = power_stats.aggregate([match, project, group]);
However this makes my _id into [y: 2016, m: 5, d: 25] which is the form of aggregation that I want, however it will be completely useless if I want to do a conditional find with the date later on with this data.
How can I preserve a UNIX datestamp with MongoDBe aggregation?

Answer 1

to achieve that you can do:
Add t field in $project phase and keep populating it thru pipeline - so there will be always reference to oryginal timestamp
Create dateTime field 'time: new Date("$_id.year", "$_id.month", "_id.day");'
var group = {
"$group" : {
"_id" : {
"year" : "$y",
"month" : "$m",
"day" : "$d",
"test" : "$test"
},
prod : {
$sum : "$prod"
},
dateTime : {
$addToSet : new Date("$_id.year", "$_id.month", "$_id.day")
}
}
};