Using ActiveRecord in a stand alone script can't update the value

[Zhengquan]

The former talks about this issue can be found at StackOverFlow
I used ActiveRecord in a stand alone script without rails runner.

The Environment is listed below.

rails:3.1.1
ActiveRecord:3.1.1

Source Code:

require 'rubygems'
require 'logger'
require 'yaml'
require 'uuidtools'
require 'active_record'

module Extensions
  module UUID
    extend ActiveSupport::Concern
    included do
      set_primary_key 'id'
    end
  end
end

ActiveRecord::Base.logger = Logger.new(STDERR)

#the connection config
$archieve_config = {
  :adapter => "mysql2",
  :host => "localhost",
  :username => "root",
  :password => "password",
  :database => "database"
}

module Archieve
  class Answer < ActiveRecord::Base
    establish_connection $archieve_config
    attr_accessible :id, :content
    include Extensions::UUID
  end
end

Archieve::Answer.find_each do |answer|
  str = answer.content
  str.gsub!(/引用:原帖由[\s\S]+发表/,"")
  str.strip!
  #answer.update_attribute(:content, str)
  answer.reload
  answer.update_attributes(:content => str)
end

The table answers only has one record,the table dump file is pushed here.
Mysql Dump File

Prbolem

When I only use update_attribute, It can't update the record.
But when I replace this line with
answer.reload
answer.update_attributes(:content => str)

It indeed can update this only one record.
Is it a bug in ActiveRecord when using it stand alone.

[qoobaa]

It works well on sqlite3. Unfortunately I don't have mysql installed currently to check it.

[arunagw]

Guys can you confirm this issue??

[Zhengquan]

you can try to reproduce the issue by the mysqldump file and the ruby script.

[steveklabnik]

Do you know if this still happens on 3.2? I don't have MySQL installed at the moment, if you can't check it out, I'll install it and give it a go.

[steveklabnik]

I tried to reproduce this today, and this is what I got:

$ ruby script.rb
DEPRECATION WARNING: Calling set_primary_key is deprecated. Please use `self.primary_key = 'the_name'` instead. (called from block in <module:UUID> at script.rb:12)
D, [2012-09-14T18:16:23.537085 #34549] DEBUG -- :   Archieve::Answer Load (0.8ms)  SELECT `answers`.* FROM `answers` WHERE (`answers`.`id` >= 0) ORDER BY `answers`.`id` ASC LIMIT 1000
D, [2012-09-14T18:16:23.565698 #34549] DEBUG -- :   Archieve::Answer Load (0.4ms)  SELECT `answers`.* FROM `answers` WHERE `answers`.`id` = 1454130827364005 LIMIT 1
D, [2012-09-14T18:16:23.566276 #34549] DEBUG -- :    (0.1ms)  BEGIN
D, [2012-09-14T18:16:23.568821 #34549] DEBUG -- :    (0.4ms)  UPDATE `answers` SET `content` = '一直用着多普达的S1，现在想换换，大家推荐一款智能手机吧，要行货，价位在2K的，谢谢！ 话费能报销么？如果每个月能报销100-200的，都值得零元或低价购台iphone4合约机的', `updated_at` = '2012-09-14 18:16:23' WHERE `answers`.`id` = 1454130827364005
D, [2012-09-14T18:16:23.569521 #34549] DEBUG -- :    (0.4ms)  COMMIT

If I comment out the reload and the update_attributes, I get this:

$ ruby script.rb
DEPRECATION WARNING: Calling set_primary_key is deprecated. Please use `self.primary_key = 'the_name'` instead. (called from block in <module:UUID> at script.rb:12)
D, [2012-09-14T18:20:10.968534 #34630] DEBUG -- :   Archieve::Answer Load (0.8ms)  SELECT `answers`.* FROM `answers` WHERE (`answers`.`id` >= 0) ORDER BY `answers`.`id` ASC LIMIT 1000
D, [2012-09-14T18:20:10.982405 #34630] DEBUG -- :    (0.2ms)  BEGIN
D, [2012-09-14T18:20:10.983162 #34630] DEBUG -- :    (0.1ms)  COMMIT

This is with Rails 3.2.8.

So it would appear that this is an issue, yes.

@jonleighton @tenderlove any thoughts?

[senny]

I don't think this is an issue. I guess the problem is that the strings are modified in place using ! methods. I created a standalone script that reproduces the issue:

# -*- coding: utf-8 -*-
require 'active_record'

ActiveRecord::Base.logger = Logger.new(STDERR)
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Schema.define do
  create_table :answers do |t|
    t.text :content
  end
end

class Answer < ActiveRecord::Base; end

Answer.create! content: "Some Content   "

Answer.find_each do |answer|
  str = answer.content

  str.strip!
  # str = str.strip # this works

  answer.update_attributes(:content => str)
end

If you use str = str.strip in place of strip! it updates correctly. The problem is that strip! will modify the version String that is held by the AR instance answer. When update attributes is called AR compares the string to only update the changed fields. Using strip! the fields are equal and hence no update.

[senny]

I'm closing this issue because I don't think it is a bug.

@Zhengquan If my previous response was not the source of the problem, please comment and I'll reopen.