module RailsConnector
  module BlobOracle
    def self.included(base)
      base.instance_eval do
        define_method :store_data do
          store_data_atomically { |f| fetch_into_file(f) }
        end
      end
    end

    def fetch_into_file(file)
      blob = blob_handle
      while data = blob.read(buff_size ||= 1.megabyte)
        file <<  data
        data = nil
        GC.start
      end
    ensure
      blob&.close
    end

    private

    def sql
      %(
        SELECT blob_data
        FROM #{self.class.table_name}
        WHERE #{self.class.primary_key} = :1
      )
    end

    def blob_handle
      con = self.class.connection.raw_connection
      con.exec(sql, id).fetch.first
    end
  end
end