2011-06-28

Symbolic Link on Windows

windows

What

You can use Symbolic links, Hard Links, and Junctions on Windows.

Insall(for 32bit) , How to use command

download symlink-1.05-x86.cab
uncompress
move DIR of symlink-1.05-x86 to Your Path.(for example : C:\Documents and Settings\YourName\)
add Path(for example : C:\Documents and Settings\YourName\symlink-1.05-x86)
open command prompt.
use ln command that seems like Unix ln Command, as follows.

> ln -s foo bar

I am on Windows XP Professional Version 2002 Service Pack 3.

Reference

http://homepage1.nifty.com/emk/symlink.html

2011-06-24

Pipe Viewer : monitoring the progress

linux

What

Pipe Viewer is a terminal-based tool for monitoring the progress of data through a pipeline.

Install(for i386)

wget http://pipeviewer.googlecode.com/files/pv-1.2.0-1.i386.rpm
sudo rpm -i pv-1.2.0-1.i386.rpm

other version : http://en.sourceforge.jp/projects/freshmeat_pv/releases/

Check install

% pv --version
pv 1.2.0 - Copyright(C) 2010 Andrew Wood <andrew.wood@ivarch.com>

Web site: http://www.ivarch.com/programs/pv.shtml

This program is free software, and is being distributed under the
terms of the Artistic License 2.0.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

How to use pv

don't use pv.

% gzip access.log > access.log.gz

use pv.

% pv access.log | gzip > access.log.gz
 520MB 0:00:08 [65.1MB/s] [================>                                            ] 28% ETA 0:00:19

other

% man pv

Refarence

http://www.ivarch.com/programs/pv.shtml

2011-06-23

Customizing the MySQL Prompt

mysql

MySQL Prompt is default.

mysql>

I like this customizing that is [user name]@[host][selected database name], as follows.

root@localhost[hoge]>

Change the mysql> prompt using my.cnf or configration file for shell.

for example .zshrc, as follows.

export MYSQL_PS1='\U[\d]> '

for example my.cnf, as follows.

[mysql]
prompt='\\U[\\d]> '

you can customize the MySQL Prompt if you want. http://dev.mysql.com/doc/refman/5.0/en/mysql-commands.html

2011-05-10

Autoload Path and Nest

rails

I have tow files hoge.rb and baz.rb.

app/models/hoge.rb

class Hoge
  class Fuga
    Baz.new
  end
end

app/models/hoge/baz.rb

class Baz
end

I have added the custom models to load path as follows.

config/environment.rb

config.autoload_paths += %W( #{RAILS_ROOT}/app/models/hoge )

Hoge::Fuga.new is LoadError: Expected in development mode as follows.

% script/console
Loading development environment (Rails 2.3.11)
>> Hoge::Fuga.new
LoadError: Expected /home/admin/apps/ad_counter/hoge/app/models/hoge/baz.rb to define Hoge::Baz
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:452:in `load_missing_constant'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:122:in `const_missing'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:463:in `load_missing_constant'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:122:in `const_missing'
        from /home/admin/apps/ad_counter/hoge/app/models/hoge.rb:3
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:406:in `load_without_new_constant_marking'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:406:in `load_file'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:547:in `new_constants_in'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:405:in `load_file'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:285:in `require_or_load'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:451:in `load_missing_constant'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:106:in `const_missing'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:118:in `const_missing'
        from (irb):1

Next is production mode as follows.

% script/console production
Loading production environment (Rails 2.3.11)
/usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:452:in `load_missing_constant': Expected /home/admin/apps/ad_counter/hoge/app/models/hoge/baz.rb to define Hoge::Baz (LoadError)
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:122:in `const_missing'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:463:in `load_missing_constant'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:122:in `const_missing'
        from /home/admin/apps/ad_counter/hoge/app/models/hoge.rb:3
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:184:in `require'
        from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.11/lib/active_support/dependencies.rb:291:in `require_or_load'
         ... 18 levels...
        from /usr/local/lib/ruby/1.8/irb/init.rb:250:in `load_modules'
        from /usr/local/lib/ruby/1.8/irb/init.rb:21:in `setup'
        from /usr/local/lib/ruby/1.8/irb.rb:54:in `start'
        from /usr/local/bin/irb:13

raise is activesupport-2.3.11/lib/active_support/dependencies.rb L 452

452         raise LoadError, "Expected #{file_path} to define #{qualified_name}" unless uninherited_const_defined?(from_mod, const_name)

It's OK when baz.rb file in app/models derectory.

% script/console
Loading development environment (Rails 2.3.11)
>> Hoge::Fuga.new
=> #<Hoge::Fuga:0xb7686ed0>

I am on Ruby 1.8.6, Rails 2.3.11, CentOS 5.3.

2011-04-12

簡単にload averageを上げるワンライナー

Linux

あるサーバのロードアベレージを高い状態で維持したかったのですが、JMeterなどでテストを作るのも面倒だったため、簡単に出来ないかなと思いやってみました。

ワンライナー

for i in {0..9}; do nohup `while :; do echo 1 > /dev/null; done;` & done

上記の場合、10個の無限ループプロセスが生成されますので、ロードアベレージは 10 まで上がり安定します（実験環境の場合）。これは負荷はCPUにかかっており、メモリを沢山消費させたり、IOの負荷を出したい場合は別の方法でやる必要があります。”本番で起こりそうなリアルな負荷”を再現したいのであれば、もっと工夫が必要です。

環境

	OS		CentOS release 5 (Final)
	shell		zsh

他にもやり方あると思いますので、教えてくださいm(_ _)m

2011-03-09

Railsのfind_by_sqlとSTIについて

rails

STI 時に find_by_sql で返すインスタンスのクラスについて調べてみました。activerecord-1.13.2 と activerecord-2.3.11 で挙動を調べました。

activerecord-1.13.2/lib/active_record/base.rb

 427       # Works like find(:all), but requires a complete SQL string. Examples:
 428       #   Post.find_by_sql "SELECT p.*, c.author FROM posts p, comments c WHERE p.id = c.post_id"
 429       #   Post.find_by_sql ["SELECT * FROM posts WHERE author = ? AND created > ?", author_id, start_date]
 430       def find_by_sql(sql)
 431         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
 432       end

 885         # Finder methods must instantiate through this method to work with the single-table inheritance model
 886         # that makes it possible to create objects of different types from the same table.
 887         def instantiate(record)

activerecord-2.3.11/lib/active_record/base.rb

 642       # Executes a custom SQL query against your database and returns all the results.  The results will
 643       # be returned as an array with columns requested encapsulated as attributes of the model you call
 644       # this method from.  If you call <tt>Product.find_by_sql</tt> then the results will be returned in
 645       # a Product object with the attributes you specified in the SQL query.                                                                                                                                  
 646       #
 647       # If you call a complicated SQL query which spans multiple tables the columns specified by the
 648       # SELECT will be attributes of the model, whether or not they are columns of the corresponding
 649       # table.
 650       #
 651       # The +sql+ parameter is a full SQL query as a string.  It will be called as is, there will be
 652       # no database agnostic conversions performed.  This should be a last resort because using, for example,
 653       # MySQL specific terms will lock you to using that particular database engine or require you to
 654       # change your call if you switch engines.
 655       #
 656       # ==== Examples
 657       #   # A simple SQL query spanning multiple tables
 658       #   Post.find_by_sql "SELECT p.title, c.author FROM posts p, comments c WHERE p.id = c.post_id"
 659       #   > [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "first_name"=>"Quentin"}>, ...]
 660       #
 661       #   # You can use the same string replacement techniques as you can with ActiveRecord#find
 662       #   Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]
 663       #   > [#<Post:0x36bff9c @attributes={"first_name"=>"The Cheap Man Buys Twice"}>, ...]
 664       def find_by_sql(sql)
 665         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
 666       end
 
1651         # Finder methods must instantiate through this method to work with the
1652         # single-table inheritance model that makes it possible to create
1653         # objects of different types from the same table.
1654         def instantiate(record)

前提データ

usersテーブル

id	type	name
1	HogeUser	bob
2	FugaUser	mike

fooテーブル

	id		title
	1		baz

Railsにあるクラス

class User < ActiveRecord::Base
end

class HogeUser < User
end

class FugaUser < User
end

class Foo < ActiveRecord::Base
end

activerecord-1.13.2/lib/active_record/base.rb の実行結果

typeを見て、HogeUser、FugaUserのインスタンスになります。

% script/console
>> user = User.find_by_sql("select * from users")
>> user.each {|u| p u.class }
HogeUser
FugaUser

type カラムを select から抜くと STI の効果はなくなります。

% script/console
user = User.find_by_sql("select id, name from users")
user.each {|u| p u.class }
User
User

Fooクラスでfind_by_sqlしても、typeカラムがあれば、HogeUser、FugaUserのインスタンスになります。

% script/console
user = Foo.find_by_sql("select * from users")
user.each {|u| p u.class }
HogeUser
FugaUser

typeをselectからなくして、Fooクラスでfind_by_sqlすれば、Fooクラスのインスタンスになります。

% script/console
user = Foo.find_by_sql("select id, name from users")
user.each {|u| p u.class }
Foo
Foo

もし、HogeUserクラス、FugaUserクラスが存在しない場合。ActiveRecord::SubclassNotFound が出ます。

% script/console
>> User.find_by_sql("select * from users")
  User Load (0.000236)   select * from users
ActiveRecord::SubclassNotFound: The single-table inheritance mechanism failed to locate the subclass: 'HogeUser'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite User.inheritance_column to use another column for that information.
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/base.rb:897:in `instantiate_without_callbacks'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/callbacks.rb:215:in `instantiate'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/base.rb:431:in `find_by_sql'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/base.rb:431:in `collect!'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/base.rb:431:in `find_by_sql'
        from (irb):1

activerecord-2.3.11/lib/active_record/base.rb の実行結果

typeを見て、HogeUser、FugaUserのインスタンスになります。

% script/console
>> user = User.find_by_sql("select * from users")
>> user.each {|u| p u.class }
HogeUser(id: integer, type: string, name: string)
FugaUser(id: integer, type: string, name: string)

type カラムを select から抜くと STI の効果はなくなります。

% script/console
user = Foo.find_by_sql("select * from users")
user.each {|u| p u.class }
User(id: integer, type: string, name: string)
User(id: integer, type: string, name: string)

Fooクラスを経由すると、Fooクラスとなります。ここは、activerecord-1.13.2とは違う挙動です。むしろ、find_by_sql がより直感的な挙動になったと思います。

% script/console
user = Foo.find_by_sql("select * from users")
user.each {|u| p u.class }
Foo(id: integer, title: string)
Foo(id: integer, title: string)

もし、HogeUserクラスとFugaUserクラスがActiveRecord::Baseを継承していた場合は hoge_users（fuga_users）テーブルがないとエラーが出ます。（activerecord-1.13.2ではこのエラーは出ません）

% script/console
>> User.find_by_sql("select * from users")
  SQL (0.1ms)   SET SQL_AUTO_IS_NULL=0
  User Load (0.1ms)   select * from users
  User Columns (0.2ms)   SHOW FIELDS FROM `users`
  HogeUser Columns (0.0ms)   Mysql::Error: Table 'find_by_sql.hoge_users' doesn't exist: SHOW FIELDS FROM `hoge_users`
ActiveRecord::StatementInvalid: Mysql::Error: Table 'find_by_sql.hoge_users' doesn't exist: SHOW FIELDS FROM `hoge_users`
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/connection_adapters/abstract_adapter.rb:227:in `log'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/connection_adapters/mysql_adapter.rb:324:in `execute'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/connection_adapters/mysql_adapter.rb:471:in `columns'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:1305:in `columns'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:1318:in `column_names'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:2899:in `inspect'
        from /usr/local/lib/ruby/gems/1.8/gems/wirble-0.1.3/lib/wirble.rb:432:in `output_value'
        from /usr/local/lib/ruby/1.8/irb.rb:151:in `eval_input'
        from /usr/local/lib/ruby/1.8/irb.rb:263:in `signal_status'
        from /usr/local/lib/ruby/1.8/irb.rb:147:in `eval_input'
        from /usr/local/lib/ruby/1.8/irb.rb:146:in `eval_input'
        from /usr/local/lib/ruby/1.8/irb.rb:70:in `start'
        from /usr/local/lib/ruby/1.8/irb.rb:69:in `catch'
        from /usr/local/lib/ruby/1.8/irb.rb:69:in `start'
        from /usr/local/bin/irb:13

もし、HogeUserクラス、FugaUserクラスが存在しない場合。ActiveRecord::SubclassNotFound が出ます。

>> User.find_by_sql("select * from users")
  SQL (0.5ms)   SET SQL_AUTO_IS_NULL=0
  User Load (0.4ms)   select * from users
  User Columns (0.3ms)   SHOW FIELDS FROM `users`
ActiveRecord::SubclassNotFound: The single-table inheritance mechanism failed to locate the subclass: 'HogeUser'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite User.inheritance_column to use another column for that information.
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:1671:in `instantiate'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:665:in `find_by_sql'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:665:in `collect!'
        from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.11/lib/active_record/base.rb:665:in `find_by_sql'
        from (irb):1

2011-03-08

Rails2系でuse_transactional_fixturesを使うときの注意

rails

テストは正しいと思うのに、何故か落ちる現象になりました。調べていたら、MySQLのMyISAMテーブルで use_transactional_fixtures が true にしていたことが原因であることが分かりました。

activerecord-2.3.10/lib/active_record/fixtures.rb

use_transactional_fixture についてARには以下のように書かれていました。トランザクションが使えないストレージエンジンではuse_transactional_fixturesをサポートしていないのでfalseにしましょうと書かれています。

211 # When *not* to use transactional fixtures:
212 #
213 # 1. You're testing whether a transaction works correctly. Nested transactions don't commit until all parent transactions commit,
214 #    particularly, the fixtures transaction which is begun in setup and rolled back in teardown. Thus, you won't be able to verify
215 #    the results of your transaction until Active Record supports nested transactions or savepoints (in progress).
216 # 2. Your database does not support transactions. Every Active Record database supports transactions except MySQL MyISAM.
217 #    Use InnoDB, MaxDB, or NDB instead.

まとめ

RELEASE SAVEPOINTの問題の時もそうでしたが、Rails2はトランザクションが使えるDBを推奨して作られている感じがします。

環境

	Rails		2.3.11
	MySQL		4.1.22

基本へ帰ろう

Symbolic Link on Windows

What

Insall(for 32bit) , How to use command

Reference

Pipe Viewer : monitoring the progress

What

Install(for i386)

Check install

How to use pv

Refarence

Customizing the MySQL Prompt

Autoload Path and Nest

簡単にload averageを上げるワンライナー

ワンライナー

環境

Railsのfind_by_sqlとSTIについて

activerecord-1.13.2/lib/active_record/base.rb

activerecord-2.3.11/lib/active_record/base.rb

前提データ

activerecord-1.13.2/lib/active_record/base.rb の実行結果

activerecord-2.3.11/lib/active_record/base.rb の実行結果

Rails2系でuse_transactional_fixturesを使うときの注意

activerecord-2.3.10/lib/active_record/fixtures.rb

まとめ

環境

参考