Delicatable treats for the rubies.

Been a long time. shouldn’t of left ya without a dope plugin to step to. meh. But for reals, I’ve been working way too much. Here’s a tasty sampler of some new and revived github projects:

• ActiveRecord Dumper
• Asset Tag Extensions
• Ruby Prof Request Filters
• Google Base4r extensions

ActiveRecord Dumper

script/plugin install http://github.com/blythedunham/ar_dumper

Dumper. I barely know her! I wrote this ages ago back in the Rails 1 dot 0h(mg) daze, but still works like a charm.

Easily export records to csv, yaml, or xml using the :find options, or (new) specify an array of activerecords with the :records option. AR Dumper dumps to strings or files with a paginated option, and it supports full customization of displayed headers and content with options such as  nly, :export, :procs, :methods

Book.dumper :yml, :find => {:conditions => ['author_name like ?', 'snowgiraffe'] }

Book.dumper :csv,   nly => [:author_name, :title], :records => @my_books

Asset Tag Extensions

script/plugin install git://github.com/blythedunham/javascript_tag_extensions

Your high performance web site client loading slowly? In addition to combining asset files, one of the best ways to improve client load speed is to move the javascript files and inline script tags to the bottom of the page. Even better, execute inline javascript after the document loads.  To load files at the bottom of the page use the

include_javascript_tag 'myjsfile', :defer => true

Similarly, replacing calls to javascript_tag with Asset Tag Extension’s inline_javascript renders the script at the bottom of the page. Use the n_load => true functionality use JQuery OnLoad functionality.

  <%  inline_javascript   n_load => true do %>
    alert("I love grapes");
  <% end %>

Ruby Prof Request Filters

script/plugin install http://github.com/blythedunham/ruby_prof_request_filters

Need to instantly profile a page? Output ruby prof results to your browser by adding the following params to the url: ruby_prof=true Flat graphs, html graph, whatever you need, this little tool comes in handy when your solving big problems.

Google Base: Base4r

I did some work on Dan Dukeson’s Google Base API For Ruby. Add, modify and delete items from Google Base (formerly Froogle) with Ruby.

Thus was born, ar_test_runner, a convenient plugin with a rake task to run the ActiveRecord test suites with your  code/gem/plugin load. You even can choose the ActiveRecord version and database.

Install

  gem sources -a http://gems.github.com
  sudo gem install blythedunham-ar_test_runner

Run ar_test_runner

Run all plugins and lib files against sqlite for app version

ar_test_runner DB=sqlite

Test 2.2.2 with rails_devs_for_data_integrity plugin loaded on mysql

ar_test_runner PLUGIN=rails_devs_for_data_integrity AR_DIR=/Library/Ruby/Gems/1.8/gems/activerecord-2.2.2

Rake Tasks

ar_test_runner works as a rake task, if installed as a plugin or by adding require “ar_test_runner” to the application’s Rakefile. The following example tests the applications default version of ActiveRecord with the files RAILS_ROOT/lib/my_file.rb and RAILS_ROOT/lib/my_other_file.rb loaded

rake test:activerecord:mysql FILE=lib/my_file.rb,lib/my_other_file.rb

Customize

To specify (or skip)  gems, files, dirs, and plugins ot load or build custom runs see the documentation at ar_test_runner .

Some ppt slides for you. Slide share soon to come.

SMS On Rails rdoc

script/plugin install git://github.com/blythedunham/smsonrails

At the end of the snowgiraffe SMS show, I demoed the sms on rails engine plugin. I’ll build it into a gem soon, but by using the generator there shouldn’t be any collisions, and the plugin should be version safe as everything is namespaced and modularized. Anyhow, here’s the script:

> rails dog --database=mysql
> mysqladmin -uroot create dog_development
> cd dog
> script/plugin install git://github.com/blythedunham/smsonrails
> script/generate sms_on_rails setup --default-service-provider=clickatell
> rake db:migrate
> mate config/environment.rb

Sign up for clickatell and update the environment.rb with your credentials. Alternatively, use the email gateway (specify no default service provider) and setup your mail settings.

The Generator does the following:

1. copy images and stylesheets to your public directory
2. generates 3 database migrations (the 2nd and 3rd have a 2 and 3 appended)
3. installs clickatell gem and static_record_cache plugin (for email carriers caching)
4. insert configuration into environment.rb

Join the club! Rails Devs for Data Integrity

I am a Rails Developer and I believe in data integrity. There I said it! And look, there are lots of people in the club. Jer on Rails had an awesome post in support for foreign keys a while back.

After my talk on supercharging ActiveRecord to behave in an enterprise environment at the MySQL conference, a lot of folks were interested in how to get around the Rails ActiveRecord errors that appear when one starts deifying the Rails Way and uses foreign keys and unique indexes on the database. Well I thought about it and came up with not only a list but a yet another new plugin rails_devs_for_data_integrity to help deal with some of the errors. So when someone tells you not to use foreign keys, don’t listen and join the Rails Devs for Data Integrity! Here is how to have em, and still make pretty Rails apps.

Super list….

Unique Keys

Use validates_uniqueness_of

validates_uniqueness_of introduces a query to check unique records before insert or update, but alone doesn’t guaranty uniqueness in a multi server/multi mongrel environment. By using it conjunction with a unique key on the database, you have proper rails error messages and your safety belt to retain data integrity. In most cases when dealing with a single instance (a single user’s user name for example), I can afford to eat the overhead of the rails validates_uniqueness_of query.

Use on duplicate key update and ignore

ar-extensions 0.9.1 supports ON DUPLICATE KEY UPDATE and IGNORE for MySQL on import, save, and create (all inserts and updates). This is especially practical for import (bulk insert) where validating each record’s uniqueness would produce a lot of overhead.

Catch and Handle the Duplicate Violation Exception

I wrote a lot of custom code in models and controllers to catch MySQL duplicate key error (ActiveRecord::StatementInvalid) and handle them appropriately. Typically, I added a new error to ActiveRecord::Base.errors, which is then displayed nicely with error_messages_for in the view. Sometimes this was done often with a save_safe model method possibly aliased to save or a rescue on the controller action.

After MySQLConf I decided to write a little plugin rails_devs_for_data_integrity to convert exceptions into ActiveRecord errors (like validations do) for tables with unique and foreign keys . Its still infantile (and without tests, gasp!) but if anyone likes to find bugs, hit me up on githubs new issue tracker. If there is more than one unique key per table, you might want write some custom error handling methods.

script/plugin install git://github.com/blythedunham/rails_devs_for_data_integrity.git

 class User < ActiveRecord::Base
   handle_unique_key_violation  :user_name, :message => 'is taken"
   handle_foreign_key_violation :primary_email_id, :message => 'is not available'
 end

Will write ActiveRecord errors instead of nasty MySQL errors:

 >> user.errors.on(:user_name)
 => "association does not exist."

 >> user.errors.on(:primary_email_id)
 => "is a duplicate."

Overwrite rescue_action_in_public in ApplicationController

Its a good idea to either send the user to a pretty 404 static generic error page (fast) or write some custom code in rescue_action_in_public. One idea is to create DisplayableException and subclass any exceptions where the text can be displayed to the user. If this is thrown, show exeception.to_s, if not show a generic error.

def rescues_action_in_public(exception)
  @message = if exception.is_a?(DisplayableException)
    exception.to_s
  else
    "Sorry but an error occurred. Please contact your mommy."
  end
  render :action => 'error_page'
end

Foreign Keys

I have been using the Redhills foreign key migration plugin for a long time and haven’t had too much trouble with foreign key violations.

Trouble Deleting Records

At one point ON DELETE was not specified to SET NULL or CASCADE on many dependent columns and there was trouble deleting rows. Reindexing the database with this option was the solution. Similarly,  one could use ON UPDATE on foreign key indexes.  However, due to the way ActiveRecord works and doesn’t really update id columns, I haven’t had any issues.

Foreign Key Validation Errors

This has happened so seldom that I never worried about it. That’s what the refresh button is for! Perhaps its because most users have their own data and aren’t really modifying and deleting simultaneously. However, sure this can happen and it throws an ActiveRecord::StatementInvalid exception as with unique key violations. I would recommend the same approach as for unique keys: catch and handle the exception. I added foreign key support to the rails_devs_for_data_integrity plugin experiment. Yay!

Today I present Taking Active Record To the Next Level at the MySQL Conference and Expo! There is a lot of excitement in the Rails world due to Rails 3 merge with Merb which will provide framework agnosticism for the people. However, good, old, (sometimes not playing nice with MySQL) ActiveRecord is still the defacto despite the cool newcomers. Don’t worry. I bashed my head against the wall with it for 3 years so you don’t have to. There are lots of tips and tricks for unleashing the power of MySQL and whipping ActiveRecord into enterprise ready shape. Oh, and also included are some really cool pictures like the giraffe on the left.

script/plugin install git://github.com/zdennis/ar-extensions.git
gem install ar-extensions

While the original functionality of database agnostic ar-extensions is to import (bulk insert) many records quickly, my favorite new features for 0.9.1 are the new find and save options which allow developers to quickly customize queries without writing SQL for the MySQL database.

Find

For instance, suppose the wrong index is used to perform your favorite query. This use to mean that the developer had to dig through the logs, find the generated query, and rewrite the entire query with the correct index in SQL and execute it with ActiveRecord::Base.find_by_sql. With ar-extensions, its just another parameter to the find method. Similarly, leveraging MySQL functionality such as SQL_CACHE, HIGH PRIORITY, and LOCK IN SHARED MODE is just as easy.

Beer.find :all, :index_hint => 'USE INDEX (uk_beer_name)'
#SQL: SELECT * from `beers` USE INDEX (uk_beer_name)

Beer.find :all, :keywords => ' SQL_CACHE HIGH_PRIORITY'
#SQL: SELECT SQL_CACHE HIGH_PRIORITY * from `beers`  

Beer.find :all, :post_sql => ' FOR UPDATE', :pre_sql => '/* My little comment*/'
#SQL: /* My little comment*/ SELECT * from `beers` FOR UPDATE 

Finder SQL Exposed

And if that’s not enough to take advantage of MySQL query options, finder_sql_to_string will send the query string back and you can gsub your heart out before execution. It’s also a great to use for debugging purposes.

sql = Beer.send :finder_sql_to_string, :conditions => ['flavor like ?', 'delicious']
Beer.find_by_sql sql.gsub('WHERE', 'where /* I heart lowercase */')

Save and Create

As for save and create, the new options provide more control over database inserts and updates, especially when unique keys are involved.

Animal.create!({:name => 'Jerry Giraffe'},   n_duplicate_key_update => [:password])
#INSERT INTO animals (`name`, `fav_beer`, `password`) VALUES('Jerry Giraffe', 'Pabst', NULL) ON DUPLICATE KEY UPDATE `animals`.`password`=VALUES(`password`)

animal.save(:keywords => 'LOW_PRIORITY', :ignore => true,
            :pre_sql => "/* Now I know where this query is coming from within my Rails code!*/")
#/* Now I know where this query is coming from within my Rails code!*/ UPDATE LOW_PRIORITY IGNORE `animals` SET `fav_beer` = 'Pabst', `password` = 'frenchfry', `name` = 'Party Giraffe' WHERE `id` = 1

In addition to these spiffy new features, ar-extensions provides support for all of these:

• (new) create and save options rdoc
• (new) find options rdoc
• (new) insert_select from one table to another rdoc
• (new) find and count unions rdoc
• (new) delete options rdoc
• import (bulk insert) with synchronization rdoc
• csv export rdoc
• better finder hash support rdoc
• disabling foreign keys rdoc
• fulltext search support rdoc
• temporary table manipulation rdoc

That’s a lot of rope! If you do by chance hang yourself, please send bugs, comments and even patches to the new github issue tracker.

# Insert one copy of each book into the shopping cart. 
  CartItem.insert_select(:from => :book,
                         :select => ['books.id, ?, ?, ?, now()', @cart.to_param, 1, Time.now],
                         :into => [:book_id, :shopping_cart_id, :copies, :updated_at, :created_at]})

# GENERATED SQL example (MySQL):
# INSERT INTO `cart_items` ( `book_id`, `shopping_cart_id`, `copies`, `updated_at`, `created_at` )
# SELECT books.id, '134', 1, '2009-03-02 18:28:25', now() FROM `books`

Using the :keywords, :pre_sql, and :post_sql the  insert_select options, support all mysql options available to insert and select statements including

• IGNORE
• ON DUPLICATE KEY UPDATE
• LOW_PRIORITY
• SQL_CACHE
• DELAY

before and after comments and anything you can imagine you want to customize.

To install:

script/plugin install git://github.com/zdennis/ar-extensions.git

For more documentation, refer to  insert_select rdocs and main rdocs.

Customize your primary keys. Pic by Kerri on flickr.

Although the standard MySQL type for id columns is an unsigned int, Rails has no support for them and uses regular signed int(11) as the default for primary keys. In addition, most of my tables are less than 16 million rows (max rows for an unsigned mediumint) and so it saves space to use smaller sized numeric types such as smallint or mediumint to save space.

Inspired by Rob Anderton’s patch which was dismissed as an uncommon requirement, I built yet another plugin to allow customization of primary keys, support unsigned integers and allow users to specify column width for numeric types.

script/plugin install http://github.com/blythedunham/mysql_migration_optimizer/tree/master

Rails ignores signs! pic by alex suarez flikr

Specifying Column Width and Unsigned Integers

The MySQL connection adapter was ignoring the :precision and :scale options and so I just loaded em up to allow unsigned numeric types and allow column width to be specified which was supported on postgresql but not MySQL.

add_column :giraffe, :beer_count, :integer, :limit => 2, :precision => :unsigned, :scale => 4
#SQL: ALTER TABLE `giraffe` ADD `beer_count` smallint(4) UNSIGNED

• :limit determines the numeric type. Rails introduced smart integer columns in 2.1 which more or less translates to the number of bytes needed for storage. Here’s a little map taken from the adapter code. Do be careful, however, as some versions of Rails (2.1) break foreign keys.
  

  :limit	Numeric Type	Column Size
  1	tinyint	1 byte
  2	smallint	2 bytes
  3	mediumint	3 bytes
  nil, 4, 11	int(11)	4 bytes
  5 to 8	bigint	8 bytes

• :scale: column width explained here by Matt Thommes number in parenthesis (4) .
• :precision : specify :signed or :unsigned. Default will be :unsigned unless you specify set MySqlMigrationOptimizer.default_sign = :signed
  in your enviroment.rb.

Customizing Primary Keys

create_table "animal", :force => true,  :primary_column => {:type=>:integer, :limit => 3, :scale=>5}  do |t| end
#SQL: CREATE TABLE `animal` ( `id` mediumint(5) UNSIGNED NOT NULL auto_increment PRIMARY KEY) ENGINE=InnoDB

If you really want to get crazy you can specify some other type. Here’s the rope, I’ll leave the room if you want to hang yourself.

# Specify a string column as the primary key
create_table "blah", :force => true,
:primary_column => {:type=>:string, :limit=>25, :auto_increment=>false} do |t|#
end

#SQL: CREATE TABLE `blah` (`id` varchar(25) NOT NULL PRIMARY KEY) ENGINE=InnoDB

Do be careful to use the same numeric type for the foreign key columns as the referenced id column.

add_column   ther_table, :blah_id, :integer, :limit => 3, :scale=>5

If you have already generated a lot of tables and do not want to change all the old column types, specify the default to be :signed in config/environment.rb. Any new columns should then specify :precision => :unsigned

MySqlMigrationOptimizer.default_sign = :signed

The schemadumper has been amended to work correctly.

Every blog post could use a finger monkey

The vanilla rails ActiveRecord finders do not allow us to specify the :select clause when associations are eager loaded with the :include option. There has been ticket after ticket on the rails site the proposed  patches were rejected on the grounds that an alternative, such as ActiveRecordContext (a fantasic plugin by the way) should be used instead.
From the database perspective, selecting fewer columns can give  huge performance boosts in some situations especially when the selected fields are indexed. However, often when joined tables are sparse (many base table records are pointing to the same joined table records), you might be better off running two queries: one on the base table, followed by a second on the join table with the collected foreign keys. To illustrate this, an employee has a fairly unique address while she shares her position in the company with several others.

Employee.find :all, :include => :position

would probably be less efficient than

employees = Employee.find :all

positions = Positions.find :all, :conditions => ['id in (?)', employees.collect(&:id)]

employees.each{|employee| employee.position = positions.select {|p| p.to_param == employee.posistion_id}

This is exactly what active record context does but without the messy details. In addition, the records are cached so any subsequent references to the associations hit the cache instead of rerunning a query.

employees = Employee.find :all
Positions.preload(employees)

On the other hand, provided that a reasonable number of records are queried, including the address would probably be more efficient.

Employee.find :all, :include => :address, :select => 'addresses.city, employees.*'

In this case wouldn’t it be great to use a :select clause if for instance you were only interested in for instance the city. To achieve this, I updated the eload select plugin. It does use some tricky parsing but does have the advantage of accepting aliases and allowing you to select from the base table (some alternates include all base columns).

One disadvantage of using :select is a lot of overhead is spent in rails on aliasing columns. Its really nasty in there and probably the reason that :select is not supported with :include out of the box.

If you really are having performance issues, its probably best to abandon the :include altogether and rewrite it as a :join.

employees = Employee.find :all, :select => 'addresses.city as address_city, employees.*',

:joins => 'left outer join addresses on addresses.id = employees.address_id'

employees.first['address_city']

Stefan Kaes has written an excellent plugin called piggy back that does this for you with belongs_to and has_one relationships. For common delegated fields, this plugin is a winner.

Employees.find :all, :piggy => 'address_city'

employees.first.address_city

So in conclusion, install eload-select plugin and you get :select and :include playing happily together. However, sometimes its not the best option out there. There is a huge open source toolbox. Use them wisely.

Install

script/plugin install git://github.com/blythedunham/static_record_cache.git

Documentation

class SomeStaticClass < ActiveRecord::Base
  acts_as_static_record
end

#cache hits
SomeStaticClass.find_by_name('blah')
SomeStaticClass.find_by_id(5)
SomeStaticClass.find :all
assoc_class.some_static_class

One can specify the cache key for faster lookups and also customize the finder SQL for the class. More documentation can be found in the rdocs.

Another, simpler method of caching can be used by folks using the active record context plugin by technoweenie. Extending StaticRecordCache will permanently cache data for the class regardless of context. This however, only caches by id.

class TelephoneCarriers < ActiveRecord::Base
  extend StaticActiveRecordContext
end

Be sure to install active_record_cache plugin:

script/plugin install http://svn.techno-weenie.net/projects/plugins/active_record_context/