=head1 INTRODUCTION
-So, you are bored with SQL, and want a native Perl interface for your
-database? Or you've been doing this for a while with L<Class::DBI>,
-and think there's a better way? You've come to the right place. Let's
-look at how you can set and use your first native L<DBIx::Class> tree.
+You're bored with SQL, and want a native Perl interface for your database? Or
+you've been doing this for a while with L<Class::DBI>, and think there's a
+better way? You've come to the right place.
-First we'll see how you can set up your classes yourself. If you want
-them to be auto-discovered, just skip to the next section, which shows
-you how to use L<DBIx::Class::Loader>.
+=head1 THE DBIx::Class WAY
+
+Here are a few simple tips that will help you get your bearings with
+DBIx::Class.
+
+=head2 Tables become Result classes
+
+DBIx::Class needs to know what your Table structure looks like. You
+do that by defining Result classes. Result classes are defined by
+calling methods proxied to L<DBIx::Class::ResultSource>. Each Result
+class defines one Table, which defines the Columns it has, along with
+any Relationships it has to other tables. (And oh, so much more
+besides) The important thing to understand:
+
+ A Result class == Table
+
+(most of the time, but just bear with my simplification)
+
+=head2 It's all about the ResultSet
+
+So, we've got some ResultSources defined. Now, we want to actually use those
+definitions to help us translate the queries we need into handy perl objects!
+
+Let's say we defined a ResultSource for an "album" table with three columns:
+"albumid", "artist", and "title". Any time we want to query this table, we'll
+be creating a L<DBIx::Class::ResultSet> from its ResultSource. For example, the
+results of:
+
+ SELECT albumid, artist, title FROM album;
+
+Would be retrieved by creating a ResultSet object from the album table's
+ResultSource, likely by using the "search" method.
+
+DBIx::Class doesn't limit you to creating only simple ResultSets -- if you
+wanted to do something like:
+
+ SELECT title FROM album GROUP BY title;
+
+You could easily achieve it.
+
+The important thing to understand:
+
+ Any time you would reach for a SQL query in DBI, you are
+ creating a DBIx::Class::ResultSet.
+
+=head2 Search is like "prepare"
+
+DBIx::Class tends to wait until it absolutely must fetch information from the
+database. If you are returning a ResultSet, the query won't execute until you
+use a method that wants to access the data. (Such as "next", or "first")
+
+The important thing to understand:
+
+ Setting up a ResultSet does not execute the query; retrieving
+ the data does.
+
+=head2 Search results are returned as Rows
+
+Rows of the search from the database are blessed into
+L<DBIx::Class::Row> objects.
+
+=head1 SETTING UP DBIx::Class
+
+Let's look at how you can set and use your first native L<DBIx::Class> tree.
+
+First we'll see how you can set up your classes yourself. If you want them to
+be auto-discovered, just skip to the next section, which shows you how to use
+L<DBIx::Class::Schema::Loader>.
=head2 Setting it up manually
-First, you'll need a base class. It should inherit from DBIx::Class
-like this:
+First, you should create your base schema class, which inherits from
+L<DBIx::Class::Schema>:
+
+ package My::Schema;
+ use base qw/DBIx::Class::Schema/;
+
+In this class you load your result_source ("table", "model") classes, which we
+will define later, using the load_namespaces() method:
+
+ # load My::Schema::Result::* and their resultset classes
+ __PACKAGE__->load_namespaces();
+
+By default this loads all the Result (Row) classes in the
+My::Schema::Result:: namespace, and also any resultset classes in the
+My::Schema::ResultSet:: namespace (if missing, the resultsets are
+defaulted to be DBIx::Class::ResultSet objects). You can change the
+result and resultset namespaces by using options to the
+L<DBIx::Class::Schema/load_namespaces> call.
+
+It is also possible to do the same things manually by calling
+C<load_classes> for the Row classes and defining in those classes any
+required resultset classes.
+
+Next, create each of the classes you want to load as specified above:
+
+ package My::Schema::Result::Album;
+ use base qw/DBIx::Class::Core/;
+
+Load any additional components you may need with the load_components() method,
+and provide component configuration if required. For example, if you want
+automatic row ordering:
- package MyApp::DB;
- use base qw/DBIx::Class/;
+ __PACKAGE__->load_components(qw/ Ordered /);
+ __PACKAGE__->position_column('rank');
-You will also want to load some of L<DBIx::Class>'s components.
-L<DBIx::Class::Core> provides a good basic set. In addition you'll
-have to use either L<DBIx::Class::Schema> or L<DBIx::Class::DB> We'll
-use C<DB> in this introduction, since it involves less magic.
-L<Schema> is mostly useful if you want to use multiple database
-connections.
+Ordered will refer to a field called 'position' unless otherwise directed. Here you are defining
+the ordering field to be named 'rank'. (NOTE: Insert errors may occur if you use the Ordered
+component, but have not defined a position column or have a 'position' field in your row.)
- __PACKAGE__->load_components(qw/Core DB/);
+Set the table for your class:
-If you want serial/auto-incremental primary keys, you'll need to add
-the apropriate component for your db as well, for example. The
-L<DBIx::Class::PK::Auto> modules help L<DBIx::Class> keep up with
-newly generated keys in auto increment database fields.
+ __PACKAGE__->table('album');
- __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+Add columns to your class:
-Once you've loaded the components, it's time to set up your connection:
+ __PACKAGE__->add_columns(qw/ albumid artist title rank /);
- __PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
+Each column can also be set up with its own accessor, data_type and other pieces
+of information that it may be useful to have -- just pass C<add_columns> a hash:
-This method is similar to the normal L<DBI>, and can take username,
-password, and L<DBI> attribute hash as well as the DSN.
+ __PACKAGE__->add_columns(albumid =>
+ { accessor => 'album',
+ data_type => 'integer',
+ size => 16,
+ is_nullable => 0,
+ is_auto_increment => 1,
+ default_value => '',
+ },
+ artist =>
+ { data_type => 'integer',
+ size => 16,
+ is_nullable => 0,
+ is_auto_increment => 0,
+ default_value => '',
+ },
+ title =>
+ { data_type => 'varchar',
+ size => 256,
+ is_nullable => 0,
+ is_auto_increment => 0,
+ default_value => '',
+ },
+ rank =>
+ { data_type => 'integer',
+ size => 16,
+ is_nullable => 0,
+ is_auto_increment => 0,
+ default_value => '',
+ }
+ );
-With that out of the way, we can define our first table class:
+DBIx::Class doesn't directly use most of this data yet, but various related
+modules such as L<DBIx::Class::WebForm> make use of it. Also it allows you to
+create your database tables from your Schema, instead of the other way around.
+See L<DBIx::Class::Schema/deploy> for details.
- package MyApp::DB::Album;
- use base qw/MyApp::DB/;
+See L<DBIx::Class::ResultSource> for more details of the possible column
+attributes.
-Then we specify which table it uses,
+Accessors are created for each column automatically, so My::Schema::Result::Album will
+have albumid() (or album(), when using the accessor), artist() and title()
+methods.
- __PACKAGE__->table('album');
+Define a primary key for your class:
-and specify which columns it has.
+ __PACKAGE__->set_primary_key('albumid');
- __PACKAGE__->add_columns(qw/albumID artist title label year/);
+If you have a multi-column primary key, just pass a list instead:
-This will automatically create accessors for each of the columns, so
-that you can read/update the values in rows you've retrieved.
+ __PACKAGE__->set_primary_key( qw/ albumid artistid / );
-Also, you need to tell it which column is the primary key:
+Define this class' relationships with other classes using either C<belongs_to>
+to describe a column which contains an ID of another Table, or C<has_many> to
+make a predefined accessor for fetching objects that contain this Table's
+foreign key:
- __PACKAGE__->set_primary_key('albumID');
+ # in My::Schema::Result::Artist
+ __PACKAGE__->has_many('albums', 'My::Schema::Result::Album', 'artist');
-If you have multiple primary keys, just pass a list instead.
+See L<DBIx::Class::Relationship> for more information about the various types of
+available relationships and how you can design your own.
-That's pretty much all you need for a basic setup. If you have more
-advanced needs like using more than one database connection for the
-same class, see L<DBIx::Class::Schema>.
+=head2 Using L<DBIx::Class::Schema::Loader>
-=head2 Using L<DBIx::Class::Loader>
+This is an external module, and not part of the L<DBIx::Class> distribution.
+Like L<Class::DBI::Loader>, it inspects your database, and automatically creates
+classes for all the tables in your database. Here's a simple setup:
-This is an additional class, and not part of the L<DBIx::Class>
-distribution. Like L<Class::DBI::Loader>, it inspects your database,
-and automatically creates classes for all the tables in your
-database. Here's a simple setup:
+ package My::Schema;
+ use base qw/DBIx::Class::Schema::Loader/;
- package MyApp::DB;
- use DBIx::Class::Loader;
+ __PACKAGE__->loader_options( relationships => 1 );
- my $loader = DBIx::Class::Loader->new(
- dsn => 'dbi:SQLite:/home/me/myapp/my.db',
- namespace => 'MyApp::DB'
- );
+ 1;
- 1;
+The actual autoloading process will occur when you create a connected instance
+of your schema below.
-This should be equivalent to the manual in the section above.
-L<DBIx::Class::Loader> takes lots of other options. For more
-information, consult its documentation.
+See the L<DBIx::Class::Schema::Loader> documentation for more information on its
+many options.
+
+=head2 Connecting
+
+To connect to your Schema, you need to provide the connection details or a
+database handle.
+
+=head3 Via connection details
+
+The arguments are the same as for L<DBI/connect>:
+
+ my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db');
+
+You can create as many different schema instances as you need. So if you have a
+second database you want to access:
+
+ my $other_schema = My::Schema->connect( $dsn, $user, $password, $attrs );
+
+Note that L<DBIx::Class::Schema> does not cache connections for you. If you use
+multiple connections, you need to do this manually.
+
+To execute some SQL statements on every connect you can add them as an option in
+a special fifth argument to connect:
+
+ my $another_schema = My::Schema->connect(
+ $dsn,
+ $user,
+ $password,
+ $attrs,
+ { on_connect_do => \@on_connect_sql_statments }
+ );
+
+See L<DBIx::Class::Schema::Storage::DBI/connect_info> for more information about
+this and other special C<connect>-time options.
+
+=head3 Via a database handle
+
+The supplied coderef is expected to return a single connected database handle
+(e.g. a L<DBI> C<$dbh>)
+
+ my $schema = My::Schema->connect (
+ sub { Some::DBH::Factory->connect },
+ \%extra_attrs,
+ );
=head2 Basic usage
-Once you've defined the basic classes, you can start interacting with
-your database. The simplest way to get a column is by primary key:
+Once you've defined the basic classes, either manually or using
+L<DBIx::Class::Schema::Loader>, you can start interacting with your database.
- my $albumID = 14;
- my $album = MyApp::DB::Album->find($albumID);
+To access your database using your $schema object, you can fetch a
+L<DBIx::Class::Manual::Glossary/"ResultSet"> representing each of your tables by
+calling the C<resultset> method.
-This will run a select with C<albumID = 14> in the C<WHERE> clause,
-and return an instance of C<MyApp::DB::Artist> that represents this
-row. Once you have that row, you can access and update columns:
+The simplest way to get a record is by primary key:
- $album->title('Physical Graffiti');
- my $title = $album->title; # $title holds 'Physical Graffiti'
+ my $album = $schema->resultset('Album')->find(14);
-If you prefer, you can use the C<set_column> and C<get_column>
-accessors instead:
+This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause, and
+return an instance of C<My::Schema::Result::Album> that represents this row. Once you
+have that row, you can access and update columns:
- $album->set_column('title', 'Presence');
- $title = $album->get_column('title');
+ $album->title('Physical Graffiti');
+ my $title = $album->title; # $title holds 'Physical Graffiti'
-Just like with L<Class::DBI>, you do an C<update> to commit your
-changes to the database:
+If you prefer, you can use the C<set_column> and C<get_column> accessors
+instead:
- $album->update;
+ $album->set_column('title', 'Presence');
+ $title = $album->get_column('title');
+
+Just like with L<Class::DBI>, you call C<update> to save your changes to the
+database (by executing the actual C<UPDATE> statement):
-If needed, you can drop your local changes instead like this:
+ $album->update;
- $album->discard_changes if $album->is_changed;
+If needed, you can throw away your local changes:
-As you can see, C<is_changed> allows you to check if there are local
-changes to your object.
+ $album->discard_changes if $album->is_changed;
+
+As you can see, C<is_changed> allows you to check if there are local changes to
+your object.
=head2 Adding and removing rows
-To create a new record in the database, you can use the C<create>
-method from L<DBIx::Class::Row>. It returns a
-L<DBIx::Class::ResultSet> object that can be used to access the data
-in the new record.
+To create a new record in the database, you can use the C<create> method. It
+returns an instance of C<My::Schema::Result::Album> that can be used to access the data
+in the new record:
- my $new_album = MyApp::DB::Album->create({
- title => 'Wish You Were Here',
- artist => 'Pink Floyd'
- });
+ my $new_album = $schema->resultset('Album')->create({
+ title => 'Wish You Were Here',
+ artist => 'Pink Floyd'
+ });
Now you can add data to the new record:
- $new_album->label('Capitol');
- $new_album->year('1975');
+ $new_album->label('Capitol');
+ $new_album->year('1975');
+ $new_album->update;
-Likewise, you can remove if from the database like this:
+Likewise, you can remove it from the database:
- $new_album->delete;
+ $new_album->delete;
-or even without retrieving first. This operation takes the same kind
-of arguments as a search.
+You can also remove records without retrieving them first, by calling delete
+directly on a ResultSet object.
- MyApp::DB::Album->delete({ artist => 'Falco' });
+ # Delete all of Falco's albums
+ $schema->resultset('Album')->search({ artist => 'Falco' })->delete;
=head2 Finding your objects
-L<DBIx::Class> provides a few different ways to retrieve data from
-your database. The simplest looks something like this:
+L<DBIx::Class> provides a few different ways to retrieve data from your
+database. Here's one example:
+
+ # Find all of Santana's albums
+ my $rs = $schema->resultset('Album')->search({ artist => 'Santana' });
+
+In scalar context, as above, C<search> returns a L<DBIx::Class::ResultSet>
+object. It can be used to peek at the first album returned by the database:
+
+ my $album = $rs->first;
+ print $album->title;
- my $iter = MyApp::DB::Album->search( artist => 'Santana' );
+You can loop over the albums and update each one:
-Note that all the C<search> methods return a L<DBIx::Class::ResultSet>
-object in scalar context. So, if you want the first album:
+ while (my $album = $rs->next) {
+ print $album->artist . ' - ' . $album->title;
+ $album->year(2001);
+ $album->update;
+ }
+
+Or, you can update them all at once:
- my $album = $iter->first;
+ $rs->update({ year => 2001 });
-In list context, the C<search> methods return all of the matching
-rows:
+In list context, the C<search> method returns all of the matching rows:
- my @albums = MyApp::DB::Album->search( artist => 'Santana' );
+ # Fetch immediately all of Carlos Santana's albums
+ my @albums = $schema->resultset('Album')->search(
+ { artist => 'Carlos Santana' }
+ );
+ foreach my $album (@albums) {
+ print $album->artist . ' - ' . $album->title;
+ }
We also provide a handy shortcut for doing a C<LIKE> search:
- my $iter = MyApp::DB::Album->search_like( artist => 'Jimi%' );
+ # Find albums whose artist starts with 'Jimi'
+ my $rs = $schema->resultset('Album')->search_like({ artist => 'Jimi%' });
+
+Or you can provide your own C<WHERE> clause:
+
+ # Find Peter Frampton albums from the year 1986
+ my $where = 'artist = ? AND year = ?';
+ my @bind = ( 'Peter Frampton', 1986 );
+ my $rs = $schema->resultset('Album')->search_literal( $where, @bind );
-Or you can provide your own handmade C<WHERE> clause, like:
-
- my $iter = MyApp::DB::Album->search_literal( 'artist = ?', 'Peter Frampton' );
+The preferred way to generate complex queries is to provide a L<SQL::Abstract>
+construct to C<search>:
-The preferred way to generate complex queries is to provide a
-L<SQL::Abstract> construct to C<search>:
+ my $rs = $schema->resultset('Album')->search({
+ artist => { '!=', 'Janis Joplin' },
+ year => { '<' => 1980 },
+ albumid => { '-in' => [ 1, 14, 15, 65, 43 ] }
+ });
- my $iter = MyApp::DB::Album->search({
- artist => { '!=', 'Janis Joplin' },
- year => { '<' => 1980 },
- id => [ 1, 14, 15, 65, 43 ]
- });
+This results in something like the following C<WHERE> clause:
-For more examples of complex searches, see
-L<DBIx::Class::Manual::Cookbook>.
+ WHERE artist != 'Janis Joplin'
+ AND year < 1980
+ AND albumid IN (1, 14, 15, 65, 43)
+
+For more examples of complex queries, see L<DBIx::Class::Manual::Cookbook>.
The search can also be modified by passing another hash with
attributes:
- my $iter = MyApp::DB::Album->search(
- { artist => 'Bob Marley' },
- { page => 1, rows => 2, order_by => 'year' }
- );
+ my @albums = My::Schema->resultset('Album')->search(
+ { artist => 'Bob Marley' },
+ { rows => 2, order_by => 'year DESC' }
+ );
+
+C<@albums> then holds the two most recent Bob Marley albums.
+
+For more information on what you can do with a L<DBIx::Class::ResultSet>, see
+L<DBIx::Class::ResultSet/METHODS>.
For a complete overview of the available attributes, see
L<DBIx::Class::ResultSet/ATTRIBUTES>.
+=head1 NOTES
+
+=head2 Problems on RHEL5/CentOS5
+
+There used to be an issue with the system perl on Red Hat Enterprise
+Linux 5, some versions of Fedora and derived systems. Further
+information on this can be found in L<DBIx::Class::Manual::Troubleshooting>
+
=head1 SEE ALSO
=over 4
=item * L<DBIx::Class::Manual::Cookbook>
-=item * L<DBIx::Class::Manual::FAQ>
-
=back
=cut