Rails - Apr 2014 - Re: Cannot execute stored procedure in Rails 3 and mysql2 gem

Hello Nirmalya,

It's a very important question which you have right now, fortunately I 
think I know the answer, here I am giving you the solution ---

Solution :
When MySQL runs stored procedure it has to know that client can handle
multiple result sets.

We will create patch file for that in our initializer folder of our
application.

Create mysql2_adapter.rb file in config/initializers with the following
content:

module ActiveRecord
  class Base
  # Overriding ActiveRecord::Base.mysql2_connection
  # method to allow passing options from database.yml
  #
  # Example of database.yml
  #
  #   login: &login
  #   socket: /tmp/mysql.sock
  #   adapter: mysql2
  #   host: localhost
  #   encoding: utf8
  #
  # @param [Hash] config hash that you define in your
  #   database.yml
  # @return [Mysql2Adapter] new MySQL adapter object
  #
  def self.mysql2_connection(config)
    config[:username] = 'root' if config[:username].nil?

    if Mysql2::Client.const_defined? :FOUND_ROWS
      config[:flags] = config[:flags] ? config[:flags] |
Mysql2::Client::FOUND_ROWS : Mysql2::Client::FOUND_ROWS
    end

    client = Mysql2::Client.new(config.symbolize_keys)
    options = [config[:host], config[:username], config[:password],
config[:database], config[:port], config[:socket], 0]
    ConnectionAdapters::Mysql2Adapter.new(client, logger, options,
config)
  end

  def self.find_by_sp(sql)
    connection.select_sp(sanitize_sql(sql), "#{name} Load").collect! {
|record| instantiate(record) }
  end
  end


  module ConnectionAdapters
  class Mysql2Adapter < AbstractMysqlAdapter
    # This method is for running stored procedures.
    #
    # @param [String] the name of procedure
    #   and arguments for procedure
    # @return [Hash]
    #
    def select_sp(sql, name = nil)
      connection = ActiveRecord::Base.connection
      begin
        connection.select_all(sql, name)
      rescue NoMethodError
      ensure
        connection.reconnect! unless connection.active?
      end
    end
  end
  end
end



If by some reason MySQL drops connection after executing stored
procedure, then we have to restore it before doing anything else. For
that purpose we have created the select_sp(sql, name = nil).

This method does several things:

  * it intercepts NoMethodError that could be raised when your procedure
returns nothing
  * it restores connection if it was dropped

So now you can run ActiveRecord::Base.procedure("CALL procedure()")
without any errors and get a hash with results.


I think it will help you.

Best Regards,
Zinia Dutta Gupta.

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