ANN: Sequel 1.3 Released


Sharon Rosner

Sequel version 1.3 has just been released. Sequel is a lightweight
database access toolkit for Ruby. Sequel provides thread safety,
connection pooling and a simple and expressive API for constructing
database queries and table schemas. Sequel also includes an ORM layer
following the ActiveRecord pattern.

The latest release of Sequel includes improved model associations and
many bug fixes. Following is a summary of the changes:

=== Better model associations

The latest release of sequel_model includes a new associations
functionality written by Jeremy Evans which replaces the old relations
code in previous versions. Please note that this version is not
completely backward-compatible and you should therefore upgrade with

The new implementation supports three kinds of relations: one_to_many,
many_to_one and many_to_many, which correspond to has_many, belongs_to
and has_and_belongs_to_many relations in ActiveRecord. In fact, the
new implementation includes aliases for ActiveRecord assocation macros
and is basically compatible with ActiveRecord conventions. It also
supports DRY implicit class name references. Here's a simple example:

class Author < Sequel::Model
has_many :books # equivalent to one_to_many

class Book < Sequel::Model
belongs_to :author # equivalent to many_to_one
has_and_belongs_to_many :categories # equivalent to many_to_many

class Category < Sequel::Model
has_and_belongs_to_many :books

These macros will create the following methods:

* Author#books, Author#add_book, Author#remove_book
* Book#author, Book#categories, Book#add_category,
* Category#books, Category#add_book, Category#remove_book

Unlike ActiveRecord, one_to_many and many_to_many association methods
return a dataset:

a = Author[1234]
a.books.sql #=> 'SELECT * FROM books WHERE (author_id = 1234)'

You can also tell Sequel to cache the association result set and
return it as an array:

class Author < Sequel::Model
has_many :books, :cache => true

Author[1234].books.class #=> Array

You can of course bypass the defaults and specify class names and key

class Node < Sequel::Model
belongs_to :parent, :class => Node
belongs_to :session, :key => :producer_id

Another useful option is :eek:rder, which sets the order for the
association dataset:

class Author < Sequel::Model
has_many :books, :eek:rder => :title

Author[1234].books.sql #=> 'SELECT * FROM books WHERE (author_id =
1234) ORDER BY title'

More information about associations can be found in the Sequel

=== Other changes

* Added configuration file for running specs (#186).

* Changed Database#drop_index to accept fixed arity (#173).

* Changed column definition sql to put UNSIGNED constraint before
unique in order to satisfy MySQL (#171).

* Enhanced MySQL adapter to support load data local infile_, added
compress option for mysql connection by default (#172).

* Fixed bug when inserting hashes in array tuples mode.

* Changed SQLite adapter to catch RuntimeError raised when executing a
statement and raise Error::InvalidStatement with the offending SQL and
error message (#188).

* Fixed Dataset#reverse to not raise for unordered dataset (#189).

* Added Dataset#unordered method and changed #order to remove order if
nil is specified (#190).

* Fixed reversing order of ASC expression (#164).

* Added support for :null => true option when defining table columns

* Fixed Symbol#method_missing to accept variable arity (#185).

=== More info on Sequel

Sequel project page:

Sequel documentation:

Join the Sequel-talk group:

Join Sequel discussion on IRC at #sequel.

Install the gem:
sudo gem install sequel

Or check out the source and install manually:
svn co sequel
cd sequel
rake install


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