MongoDB count by date AND to date - ruby-on-rails

Question

I have a User table with "created" date field. Now I want to know how many new users were created on each day last week, as well as the total users by the end of each day (since the beginning of time).
For example:
{
{
day: 27,
new_users: 5,
total_users: 100
}, {
day: 28,
new_users: 7,
total_users: 107
}, {
day: 29,
new_users: 2,
total_users: 109
}
}
I already got the new_users part by using simple grouping and summing. Code below is mongoid/Ruby.
results = User.collection.aggregate(
[{
"$match" => {
created: { "$gte" => 1.week.ago.beginning_of_day, "$lte" => Time.now }
}
},
{
"$group" => {
_id: {
year_joined: { "$year" => "$created" },
month_joined: { "$month" => "$created" },
day_joined: { "$dayOfMonth" => "$created" }
},
count: { "$sum" => 1 }
}
},
{
"$sort" => {"_id.year_joined" => 1, "_id.month_joined" => 1, "_id.day_joined" => 1}
}]
)
How do I also get the total_users in the results?

Answer 1

You're getting close with your attempt. One thing is that since you're starting out by filtering down to own the last week, you don't need to care about the year or month.
Note: I don't know ruby, so I wrote it as I would in the mongo shell.
{
"$match" => {
created: { "$gte" => 1.week.ago.beginning_of_day, "$lte" => Time.now }
}
},
{
$group: {
_id: {"$dayOfMonth": "$created" },
day: {"$dayOfMonth": "$created" },
newUsers: { "$sum": 1}
}
},
{
"$sort" => {"_id.year_joined" => 1, "_id.month_joined" => 1, "_id.day_joined" => 1}
}
That will get you the day and newUsers, but it wont get you the total. I don't actually that is possible in a single query. One alternative might be to give each user a unique number and just take the max of the numbers for that day.