Plot records over time in your rails console

timeplot.rb

# Example usage:
#   timeplot User.all
#   timeplot User.all, bucket_size: day, field: :updated_at
#
# Arguments:
#   bucket_size: One of [:day, :month, :year]. Defaults to :month.
#   field: Timestamp field to plot against. Defaults to :created_at.
class TimePlot
  BUCKET_SIZES = [:day, :month, :year]
  X_AXIS_MAX = 100

  attr_reader :records, :bucket_size, :field
  def initialize(records, bucket_size: :month, field: :created_at)
    @records = records
    @bucket_size = bucket_size
    @field = field
  end

  def graph
    max = buckets.values.max
    buckets.each do |timestamp, count|
      if count > 0
        puts "#{timestamp} | #{draw_line(count, max)} (#{count})"
      else
        puts "#{timestamp} |"
      end
    end; nil
  end

  def counts
    buckets.each do |timestamp, count|
      puts "#{timestamp} - #{count}"
    end; nil
  end

  private

  def timestamp_for(record)
    record.send(field)
  end

  def buckets
    @_buckets ||= (
      result = Hash.new(0)
      last_timestamp = timestamp_for(ordered_records.first)

      ordered_records.find_in_batches do |batch|
        batch.each do |record|
          this_timestamp = timestamp_for(record)

          # when we skip a bucket or more, ensure we enter 0 for all skipped buckets
          if key(this_timestamp) != key(last_timestamp) &&
              key(this_timestamp) != key(last_timestamp + 1.send(bucket_size))

            while key(this_timestamp) != key(last_timestamp)
              last_timestamp += 1.send(bucket_size)
              result[key(last_timestamp)] = 0
            end
          end

          result[key(this_timestamp)] += 1
          last_timestamp = this_timestamp
        end
      end

      result
    )
  end

  def ordered_records
    records.order("#{field} ASC")
  end

  def key(timestamp)
    if bucket_size == :day
      timestamp.strftime("%d-%m-%Y")
    elsif bucket_size == :month
      timestamp.strftime("%m-%Y")
    elsif bucket_size == :year
      timestamp.strftime("%Y")
    else
      raise "Invalid bucket_size - #{bucket_size}"
    end
  end

  def draw_line(count, max)
    units = ((count.to_f / max) * X_AXIS_MAX).round
    "=" * units
  end
end

def timeplot(*args)
  TimePlot.new(*args).graph
end

TODO - I'm pretty sure this doesn't work at plotting all 0-count buckets when using a field other than created_at. Since this is doing batching, which works on primary_key (id), I don't think the ordering does anything, so the records we get aren't guaranteed to be sorted by the specified timestamp field.