Question

I want to plot a graph to see the user growth in last 30 days.

So it will an array something like this: (an incremental array)

 [0,100,250,500,1000,1100.....5000,5500]

Solution 1: A stupid way to do this is to fire query for every day:

  (30.days.ago.to_date..Date.today).map {|date| User.where("Date(created_at) <= ?" , date).count}

But this will fire 30 queries.

Solution 2: Find all records using group by option and then loop over it and sumup previous records.

 User.group('Date(created_at)').count
 (30.days.ago.to_date..Date.today).map {|date| counts[date] || 0} //and again loop over it
 //and now start summing up previous ones elements to get an another array..

But both the solutions are useless. Any suggestions to make this as optimised ones.

Answer 1

I’ll do the following :

growth = []
users =  User.group('Date(created_at)').count

(30.days.ago.to_date..Date.today).each do |day|
  growth.push(growth.sum + (users[day] || 0))
end

Not tested but you get the idea.