ActiveRecord> MySQL适配器>未定义的方法“ more_results”

Question

I have incorporated ActiveRecord into a script I am writing to process some data in a MySQL database. In my development environment, using Mac OS X, everything works fine, however, when I attempt to deploy the script in a Linux environment, I keep getting the following error:

/activerecord-3.0.0/lib/active_record/connection_adapters/mysql_adapter.rb:623:in `select': undefined method `more_results' for #<Mysql:0x915976c> (NoMethodError)

The code where this error is occuring is pasted below, specifically the second to last line that has been commented.

  def select(sql, name = nil)
    @connection.query_with_result = true
    result = execute(sql, name)
    rows = []
    result.each_hash { |row| rows << row }
    result.free
    @connection.more_results && @connection.next_result   # invoking stored procedures with CLIENT_MULTI_RESULTS requires this to tidy up else connection will be dropped 
    rows
  end

The history of why this code was introduced can be viewed at https://rails.lighthouseapp.com/projects/8994/tickets/3151-mysql-adapter-update-to-enable-use-of-stored-procedures#ticket-3151-33

That said, I am still uncertain how to fix this error without just commenting out that problematic line. I am not using any stored procedures so it is not a significant issue, however, I would like to implement a more extensible fix.

I am using the following gems in both environments.

activerecord (3.0.0) mysql (2.8.1)

Thanks in advance for any thoughts on what might be going on here!

Answer 1

I'm a newbie to Ruby (ha), and I ran into the same problem while going through this tutorial: http://guides.rubyonrails.org/getting_started.html during step 6.1 (migrate).

I simply wrapped the command in an if to ensure the method actually exists before calling it, like so:

if (@connection.respond_to?('more_results'))
      @connection.more_results && @connection.next_result    # invoking stored procedures with CLIENT_MULTI_RESULTS requires this to tidy up else connection will be dropped 
end

I was then able to complete the tutorial just fine. I don't know what the implications are in skipping that line of code, but on my little development box, it probably doesn't matter.