=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
-=head2 Setting it up manually
+Here are a few simple tips that will help you get your bearings with
+DBIx::Class.
-First, you'll need a base class. It should inherit from
-L<DBIx::Class> like this:
+=head2 Tables become Result classes
- package MyApp::DB;
- use base qw/DBIx::Class/;
+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:
-You will also want to load some of the L<DBIx::Class> components.
-L<DBIx::Class::Core> provides a good starter 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.
-C<Schema> is mostly useful if you want to use multiple database
-connections.
+ A Result class == Table
- __PACKAGE__->load_components(qw/Core DB/);
+(most of the time, but just bear with my simplification)
-If you want serial/auto-incrementing primary keys, you should use the
-L<DBIx::Class::PK::Auto> component for your database. For example, if
-you're using SQLite add C<PK::Auto::SQLite> to the list:
+=head2 It's all about the ResultSet
- __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+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!
-C<PK::Auto> classes exist for many databases; see
-L<DBIx::Class::PK::Auto> for more information.
+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:
-Once you've loaded the components, it's time to set up your
-connection:
+ SELECT albumid, artist, title FROM album;
- __PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
+Would be retrieved by creating a ResultSet object from the album table's
+ResultSource, likely by using the "search" method.
-This method is similar to the normal L<DBI> C<connect> method, and can
-take username, password, and L<DBI> attribute hash as well as the DSN.
+DBIx::Class doesn't limit you to creating only simple ResultSets -- if you
+wanted to do something like:
-With that out of the way, we can define our first table class:
+ SELECT title FROM album GROUP BY title;
- package MyApp::DB::Album;
- use base qw/MyApp::DB/;
+You could easily achieve it.
-Then we specify which table it uses,
+The important thing to understand:
- __PACKAGE__->table('album');
+ 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 should create your base schema class, which inherits from
+L<DBIx::Class::Schema>:
-and specify which columns it has.
+ package My::Schema;
+ use base qw/DBIx::Class::Schema/;
- __PACKAGE__->add_columns(qw/albumid artist title label year/);
+In this class you load your result_source ("table", "model") classes, which we
+will define later, using the load_namespaces() method:
-This will automatically create accessors for each of the columns, so
-that you can read/update the values in rows you've retrieved.
+ # load My::Schema::Result::* and their resultset classes
+ __PACKAGE__->load_namespaces();
-Also, you need to tell it which column is the primary key:
+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__->load_components(qw/ Ordered /);
+ __PACKAGE__->position_column('rank');
+
+Set the table for your class:
+
+ __PACKAGE__->table('album');
+
+Add columns to your class:
+
+ __PACKAGE__->add_columns(qw/ albumid artist title rank /);
+
+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:
+
+ __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 => '',
+ }
+ );
+
+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.
+
+See L<DBIx::Class::ResultSource> for more details of the possible column
+attributes.
+
+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.
+
+Define a primary key for your class:
__PACKAGE__->set_primary_key('albumid');
-If you have a primary key composed of multiple columns, just pass a
-list instead.
+If you have a multi-column primary key, just pass a list instead:
-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>.
+ __PACKAGE__->set_primary_key( qw/ albumid artistid / );
-=head2 Using L<DBIx::Class::Loader>
+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:
-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:
+ # in My::Schema::Result::Artist
+ __PACKAGE__->has_many('albums', 'My::Schema::Result::Album', 'artist');
- package MyApp::DB;
- use DBIx::Class::Loader;
+See L<DBIx::Class::Relationship> for more information about the various types of
+available relationships and how you can design your own.
- my $loader = DBIx::Class::Loader->new(
- dsn => 'dbi:SQLite:/home/me/myapp/my.db',
- namespace => 'MyApp::DB'
- );
+=head2 Using L<DBIx::Class::Schema::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:
+
+ package My::Schema;
+ use base qw/DBIx::Class::Schema::Loader/;
+
+ __PACKAGE__->loader_options( relationships => 1 );
1;
-This should be equivalent to the manual setup in the section above.
-L<DBIx::Class::Loader> takes lots of other options. For more
-information, consult its documentation.
+The actual autoloading process will occur when you create a connected instance
+of your schema below.
+
+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, either manually or using
-L<DBIx::Class::Loader>, you can start interacting with your database.
+L<DBIx::Class::Schema::Loader>, you can start interacting with your database.
+
+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.
+
The simplest way to get a record is by primary key:
- my $album = MyApp::DB::Album->find(14);
+ my $album = $schema->resultset('Album')->find(14);
-This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause,
-and return an instance of C<MyApp::DB::Album> that represents this
-row. Once you have that row, you can access and update columns:
+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->title('Physical Graffiti');
my $title = $album->title; # $title holds 'Physical Graffiti'
-If you prefer, you can use the C<set_column> and C<get_column>
-accessors instead:
+If you prefer, you can use the C<set_column> and C<get_column> accessors
+instead:
$album->set_column('title', 'Presence');
$title = $album->get_column('title');
-Just like with L<Class::DBI>, you do an C<update> to commit your
-changes to the database:
+Just like with L<Class::DBI>, you call C<update> to save your changes to the
+database (by executing the actual C<UPDATE> statement):
$album->update;
-If needed, you can throw away your local changes like this:
+If needed, you can throw away your local changes:
$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.
+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. It returns an instance of C<MyApp::DB::Album> 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({
+ my $new_album = $schema->resultset('Album')->create({
title => 'Wish You Were Here',
artist => 'Pink Floyd'
});
$new_album->year('1975');
$new_album->update;
-Likewise, you can remove it from the database like this:
+Likewise, you can remove it from the database:
$new_album->delete;
-You can also remove records without or 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.
# Delete all of Falco's albums
- MyApp::DB::Album->delete({ artist => 'Falco' });
+ $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. Here's one example:
+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 = MyApp::DB::Album->search({ artist => 'Santana' });
+ 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:
+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;
-Or, you can loop over the albums and update each one:
+You can loop over the albums and update each one:
while (my $album = $rs->next) {
print $album->artist . ' - ' . $album->title;
$album->update;
}
-For more information on what you can do with a
-L<DBIx::Class::ResultSet>, see L<DBIx::Class::ResultSet/METHODS>.
+Or, you can update them all at once:
+
+ $rs->update({ year => 2001 });
-In list context, the C<search> method returns all of the matching
-rows:
+In list context, the C<search> method returns all of the matching rows:
# Fetch immediately all of Carlos Santana's albums
- my @albums = MyApp::DB::Album->search({ artist => 'Carlos Santana' });
+ 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:
# Find albums whose artist starts with 'Jimi'
- my $rs = MyApp::DB::Album->search_like({ artist => 'Jimi%' });
+ my $rs = $schema->resultset('Album')->search_like({ artist => 'Jimi%' });
-Or you can provide your own handmade C<WHERE> clause, like:
+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 = MyApp::DB::Album->search_literal( $where, @bind );
+ my $rs = $schema->resultset('Album')->search_literal( $where, @bind );
-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 = MyApp::DB::Album->search({
+ my $rs = $schema->resultset('Album')->search({
artist => { '!=', 'Janis Joplin' },
year => { '<' => 1980 },
- albumid => [ 1, 14, 15, 65, 43 ]
+ albumid => { '-in' => [ 1, 14, 15, 65, 43 ] }
});
This results in something like the following C<WHERE> clause:
AND year < 1980
AND albumid IN (1, 14, 15, 65, 43)
-For more examples of complex queries, see
-L<DBIx::Class::Manual::Cookbook>.
+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 @albums = MyApp::DB::Album->search(
+ 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
projects / dbsrgits/DBIx-Class.git / blobdiff