Question

How do I go about querying a date range (of say the last 30 days from now) with Mongoid and Ruby?

I need to end up with an array or hash like the following:

{
    15 => 300,
    14 => 23,
    13 => 23
    ...
    30 => 20  # Goes over into previous month
    28 => 2
}

I am currently storing each document with a DateTime instance as well as a unix timestamp Integer field.

The keys in the above hash are the days and the values are the sum of all sales for those days.

Any ideas?

Answer 1

Here’s how to do it all in rubyland:

sales_by_date = Hash.new(0)

Sale.where(:created_at.gte => (Date.today - 30)).order_by(:created_at, :desc).each do |s|
  sales_by_date[s.created_at.strftime("%m-%d")] += 1
end

This will create a hash with “month-day” keys, reason is that some months have fewer than 30 days and will result in a key collision if the query is always 30.

If you want a different range, change the query:

# Between 10 and 20 days ago
start_day       = 10
end_day         = 20

Sale.where(:created_at.gte => (Date.today - end_day), :created_at.lte => (Date.today - start_day))

Change created_at to whatever the name of your datetime field is.