blog/traveling-time-with-postgres-range-columns/

state_tax_model.rb

class StateTax < ApplicationRecord
  attr_accessor :effective_date

  def save_temporal
    StateTax.transaction do
      raise ArgumentError, 'Effective date is not set' unless effective_date.present?
      raise ArgumentError, 'Cannot save temporal an existing record' if persisted?

      now = Time.zone.now
      new_row = self.class.new(state_id: state_id, tax_type: tax_type, rate: rate)
      new_row.effective_range = effective_date...nil
      new_row.system_range = now...nil

      if previous_row.present?
        previous_row.system_range = previous_row.system_range.first...now
        previous_row.save!
        puts new_row.effective_range.first
        puts previous_row.effective_range.first
        if new_row.effective_range.first > previous_row.effective_range.first
          new_previous_row = previous_row.dup
          new_previous_row.effective_range = new_previous_row.effective_range.first...new_row.effective_range.first
          new_previous_row.system_range = now...nil
          new_previous_row.save!
        end
      end

      if next_row.present?
        new_row.effective_range = new_row.effective_range.first...next_row.effective_range.first
      end

      new_row.save!
    end
  end

  def previous_row
    @previous_row ||= base_query.where('lower(effective_range) <= ?', effective_date).order('lower(effective_range) desc').limit(1).first
  end

  def next_row
    @next_row ||= base_query.where('lower(effective_range) > ?', effective_date).order('lower(effective_range) asc').limit(1).first
  end

  def base_query
    StateTax.where(state_id: state_id, tax_type: tax_type).where('upper(system_range) is null')
  end
end