ActiveRecord で水平分割されてるの楽に扱うやつ

horizontal_split_nyan.rb

module HorizontalSplitNyan
  def self.const_missing(const_name)
    klass = Class.new(ActiveRecord::Base)
    klass.table_name = "horizontal_split_nyans_#{const_name.to_s.downcase}"
    const_set(const_name, klass)
  end

  def self.build(&block)
    relations = table_classes.map { |c| c.instance_eval(&block) }
    sql = relations.map { |r| r.to_sql }.join(' UNION ')
    table_classes.first.from("(#{sql}) #{table_classes.first.table_name}")
  end

  def self.method_missing(method_name, *args, &block)
    build { send(method_name, *args) }
  end

  def self.tables
    tables = ActiveRecord::Base.connection.tables.select { |t| t =~ /\Ahorizontal_split_nyans_p\d{6}/ }
  end

  def self.table_classes
    tables.map do |t|
      _, year, month = *t.match(/horizontal_split_nyans_p(\d{4})(\d{2})/)
      split_post_class = SplitPost.const_get("P#{year}#{month}")
    end
  end
end

nyans = HorizontalSplitNyan.build { where(user_id: 1) }
nyan_count = HorizontalSplitNyan.build { where(user_id: 1) }.count