Checkout db connections from the pool with some friendly syntax.

data_load.rb

module DataLoad
  class Thing1
    include DatabaseConnectionHelper
 
    def reload_all
      with_master_connection do |connection|
        sql = <<-SQL
        create temporary table tmp_thing1 (
          -- ...
        )
        SQL
        connection.execute(sql)
    
        sql = <<-SQL
        --  Load data
        SQL
        connection.execute(sql)
   
        sql = <<-SQL
        --  Do things with the data
        SQL
        connection.execute(sql)
      end
    end
  end
end

database_connection_helper.rb

module DatabaseConnectionHelper
  extend ActiveSupport::Concern

  def with_master_connection(&block)
    ActiveRecord::Base.connection_pool.with_connection(&block)
  end

  def with_slave_connection(&block)
    SlaveBase.connection_pool.with_connection(&block)
  end
end