1. Introduction to DBIx::Class
Doran Barton
Bluehost
doran@bluehost.com

2. Background: DBI
● DBI is awesome
– Abstraction layer between code and database
backend
– “Easy” to migrate code from one RDBMS to another

3. DBIx::Class
● Is an ORM class

4. ORM: Object Relational Mapper
● Database tables become objects
● Table data and relationships between tables become
object methods
● Example ORMs:
– Hibernate (Java)
– SQLAlchemy (Python)
– CakePHP (PHP)
– DBIx::Class (Perl)

5. DBIx::Class
● Founded by Matt S. Trout (mst)
● Website: http://www.dbix-class.org/

6. DBIx::Class Benefits
● No more writing SQL
– (You still can, if needed.)
● Ease of use
– Put junior developers to work faster

7. DBIx::Class Caveats
● No SQL
– Figuring out how to express complex queries can be
irksome
● Startup overhead
– DBIx::Class leverages lots of other CPAN modules
● Result class code
– Rewriting CREATE TABLEs in DBIx::Class result class
code may seem redundant

8. Using DBIx::Class
● Write your schema class
● Write a result class for each table

9. Example: Simple blog schema
blog_post comment
author

10. Example: Schema class
package MyBlog::Schema;
use base qw/DBIx::Class::Schema/;
__PACKAGE__­>load_namespaces();
1;

11. Example: blog_post
CREATE TABLE blog_post (
post_id SERIAL PRIMARY KEY,
headline VARCHAR(100) NOT NULL,
post_timestamp TIMESTAMP NOT NULL DEFAULT NOW(),
author_id INTEGER NOT NULL
REFERENCES author(author_id),
body TEXT NOT NULL
);
package MyBlog::Schema::Result::BlogPost;
use base qw/ DBIx::Class::Core /;
__PACKAGE__­>table('blog_post');
__PACKAGE__­>add_columns(
qw/post_id headline post_timestamp author_id body/);
__PACKAGE__­>set_primary_key('post_id');
__PACKAGE__­>belongs_to(
author => 'MyBlog::Schema::Result::Author',
'author_id');
__PACKAGE__­>has_many(
comments => 'MyBlog::Schema::Result::Comment',
'post_id');

12. Example: author
CREATE TABLE author (
author_id SERIAL PRIMARY KEY,
username VARCHAR(20) UNIQUE NOT NULL,
enc_password VARCHAR(100) NOT NULL,
first_name VARCHAR(100) NOT NULL,
last_name VARCHAR(100) NOT NULL,
email VARCHAR(300) NOT NULL,
can_blog BOOLEAN NOT NULL DEFAULT 'f'
);
package MyBlog::Schema::Result::Author;
use base qw/ DBIx::Class::Core /;
__PACKAGE__­>table('author');
__PACKAGE__­>add_columns(
qw/author_id username enc_password first_name last_name
email can_blog/);
__PACKAGE__­>set_primary_key('author_id');
__PACKAGE__­>has_many(
posts => 'MyBlog::Schema::Result::BlogPost',
'author_id');
__PACKAGE__­>has_many(
comments => 'MyBlog::Schema::Result::Comment',
'author_id');
1;

13. Example: comment
CREATE TABLE comment (
comment_id SERIAL PRIMARY KEY,
post_id INTEGER NOT NULL
REFERENCES blog_post(post_id),
author_id INTEGER NOT NULL
REFERENCES author(author_id),
comment_dt TIMESTAMP NOT NULL DEFAULT NOW(),
body TEXT NOT NULL
);
package MyBlog::Schema::Result::Comment;
use base qw/ DBIx::Class::Core /;
__PACKAGE__­>table('comment');
__PACKAGE__­>add_columns(
qw/comment_id post_id author_id comment_dt body/);
__PACKAGE__­>set_primary_key('comment_id');
__PACKAGE__­>belongs_to(
author => 'MyBlog::Schema::Result::Author',
'author_id');
__PACKAGE__­>belongs_to(
post => 'MyBlog::Schema::Result::BlogPost',
'post_id');
1;

14. Using DBIC classes
use feature 'say';
use MyBlog::Schema;
use Lingua::EN::Inflect qw/PL_N PL_V/;
my $schema = MyBlog::Schema­>connect('dbi:Pg:dbname=myblog');
my @posts = $schema­>resultset('BlogPost')­>search(
{ 'author.username' => 'fozz', },
{ prefetch => 'author'},
)­>all;
say "There ",
PL_V("is", scalar @posts), " ",
scalar @posts, " ",
PL_N("post", scalar @posts), " by this author.";

15. DBIx::Class::Schema::Loader
● Creates result classes for you
– On-the-fly or one-time
● Can also generate CREATE TABLE commands from
schema classes

16. Example: dbicdump
● $ dbicdump -o dump_directory=./lib
-o components='["InflateColumn::DateTime"]'
MyBlog::Schema dbi:Pg:dbname=myblog

17. Dynamic DBIC
● In Schema class:
package MyBlog::Schema;
use base qw/DBIx::Class::Schema::Loader/;

18. Components/Inflating
● DBIx::Class makes it easy to coerce a table field into an
object.
– __PACKAGE__­>load_components("InflateColumn::DateTime");
● Then, specify the column type as datetime
– __PACKAGE__­>add_columns(
...
post_timestamp => { type => 'datetime' },
...
);
● For more info, see DBIx::Class::InflateColumn::DateTime

19. Other inflators
● DBIx::Class::InflateColumn::IP
– Coerces field into NetAddr::IP
● DBIx::Class::InflateColumn::URI
– Coerces field into URI
● DBIx::Class::InflateColumn::Currency
– Coerces field into Data::Currency
● And you can roll your own!

20. Learning more
● Excellent POD
– DBIx::Class::Manual::DocMap
– DBIx::Class::Manual::Intro
– DBIx::Class::Manual::Cookbook
● http://www.dbix-class.org/
● Mailing list
– http://lists.scsys.co.uk/mailman/listinfo/dbix-class
● IRC
– irc.perl.org#dbix-class