easy way to create query classes that create prepared statements through the 'sequel' library... performance impact of this is really low (query string is only stored in memory once and query execution always goes through prepared statement)

gistfile1.rb

class Query

  def self.query_name
    :return_valid_query_name_in_subclass_or_you_will_get_really_weird_results
  end

  def self.create_prepared_statement(sql, placeholders_array)
    sql = sql.super_strip unless Environment.log_sql?
    DB[sql, *placeholders_array].prepare(:select, query_name)
  end

  def self.call_prepared_statement(parameter_hash)
    DB.call(query_name, parameter_hash)
  end

end

gistfile2.rb

# this query returns an array of hashes, where each hash contains the following keys:
# :category_id, :category_name, :number_of_companies
class GetCategoriesForCityQuery < Query

  def self.query_name
    :get_categories_for_city_query
  end

  create_prepared_statement %{
      select
        cat.id as "category_id",
        cat.name as "category_name",
        count(com.*) as "number_of_companies"
      from
        categories cat
        inner join categories_companies cat_com on cat.id = cat_com.category_id
        inner join companies com on cat_com.company_id = com.id
      where
        com.city = ? and
        com.zipcode = ?
      group by
        cat.id
    }, [ :$city_name, :$zipcode ]

  def self.execute(city_name, zipcode)
    call_prepared_statement :city_name => city_name, :zipcode => zipcode
  end

end