DBIx::Class::Manual::Intro - Introduction to DBIx::Class
-=head1 Introduction.
+=head1 INTRODUCTION
-So, you are bored with SQL, and want a native perl interface for your classes?
-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 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 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 ResultSources
+
+DBIx::Class needs to know what your Table structure looks like. You do that by
+defining L<DBIx::Class::ResultSource>s. Each table gets a ResultSource, 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 ResultSource == 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.
+
+=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 MyApp::DB
- use base qw/DBIx::Class/;
+ package My::Schema;
+ use base qw/DBIx::Class::Schema/;
-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 DB in this introduction, since it involves less magic. Schema is
-mostly useful if you want to use multiple database connections.
+In this class you load your result_source ("table", "model") classes, which we
+will define later, using the load_classes() method. You can specify which
+classes to load manually:
- __PACKAGE__->load_components(qw/Core DB/);
+ # load My::Schema::Album and My::Schema::Artist
+ __PACKAGE__->load_classes(qw/ Album Artist /);
-If you want serial/auto-incremental primary keys, you'll need to add
-the apropriate component for your db as well, for example. The
-PK::Auto::* modules help L<DBIx::Class> keep up with newly generated
-keys in auto increment database fields.
+Or load classes by namespace:
- __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+ # load My::Schema::Album, My::Schema::Artist and My::OtherSchema::LinerNotes
+ __PACKAGE__->load_classes(
+ {
+ 'My::Schema' => [qw/ Album Artist /],
+ 'My::OtherSchema' => [qw/ LinerNotes /]
+ }
+ );
-Once you've loaded the components, it's time to set up your connection:
+Or let your schema class load all classes in its namespace automatically:
- __PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
+ # load My::Schema::*
+ __PACKAGE__->load_classes();
-This method is similar to the normal L<DBI>, and can take user/pass/dbi
-attribute hash as well as the dsn.
+Next, create each of the classes you want to load as specified above:
+
+ package My::Schema::Album;
+ use base qw/DBIx::Class/;
-With that out of the way, we can define our first table class:
+Load any components required by each class with the load_components() method.
+This should consist of "Core" plus any additional components you want to use.
+For example, if you want serial/auto-incrementing primary keys:
- package MyApp::DB::Album;
+ __PACKAGE__->load_components(qw/ PK::Auto Core /);
- use base qw/MyApp::DB/;
+C<PK::Auto> is supported for many databases; see L<DBIx::Class::Storage::DBI>
+for more information.
-Then we specify which table it uses,
+Set the table for your class:
__PACKAGE__->table('album');
-and specify which columns it has.
+Add columns to your class:
+
+ __PACKAGE__->add_columns(qw/ albumid artist title /);
+
+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 => '',
+ }
+ );
+
+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<SQL::Translator> 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::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');
- __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');
+ __PACKAGE__->has_many('albums', 'My::Schema::Artist', 'album_id');
-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 1 database connections 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 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;
-This should be equivalent to the manual in the section above.
-L<DBIx::Class::Loader> takes lots of other options. For more information,
-consult the reference documentation.
+The actual autoloading process will occur when you create a connected instance
+of your schema below.
-=head2 Basic Usage
+See the L<DBIx::Class::Schema::Loader> documentation for more information on its
+many options.
-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:
+=head2 Connecting
- $albumID = 14;
- $album = MyApp::DB::Album->find($albumID);
+To connect to your Schema, you need to provide the connection details. The
+arguments are the same as for L<DBI/connect>:
-This will run a select with albumID=14 in the WHERE clause, and return an instance
-of MyApp::DB::Artist that represents this row. Once you have that row, you can
-access and update columns
+ 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.
+
+=head2 Basic usage
+
+Once you've defined the basic classes, either manually or using
+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 = $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<My::Schema::Album> that represents this row. Once you
+have that row, you can access and update columns:
$album->title('Physical Graffiti');
- $title = $album->title; # $title holds '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:
-or if you prefer, you can use the set_column/get_column accessors instead
-of the autogenerated accessors based on your column names.
+ $album->set_column('title', 'Presence');
+ $title = $album->get_column('title');
-Just like with L<Class::DBI>, you do an 'update' to commit your changes
-to the database:
+Just like with L<Class::DBI>, you call C<update> to commit your changes to the
+database:
$album->update;
-If needed, you can drop your local changes instead like this:
+If needed, you can throw away your local changes:
$album->discard_changes if $album->is_changed;
-As you can see, is_changed allows you to check if there are local changes to
+As you can see, C<is_changed> allows you to check if there are local changes to
your object.
-=head2 Adding and removing rows.
+=head2 Adding and removing rows
-To create a new record in the database, you can use the '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::Album> that can be used to access the data
+in the new record:
- $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->update;
+
+Likewise, you can remove it from the database:
+
+ $new_album->delete;
+
+You can also remove records without retrieving them first, by calling delete
+directly on a ResultSet object.
+
+ # Delete all of Falco's albums
+ $schema->resultset('Album')->search({ artist => 'Falco' })->delete;
-likewise, you can remove if from the database like this:
+=head2 Finding your objects
- $new_album->delete();
+L<DBIx::Class> provides a few different ways to retrieve data from your
+database. Here's one example:
-or even without retrieving first. This operation takes the same kind of
-arguments as a search.
+ # Find all of Santana's albums
+ my $rs = $schema->resultset('Album')->search({ artist => 'Santana' });
- MyApp::DB::Album->delete({ artist => 'Falco' });
+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:
-=head2 Finding your objects.
+ my $album = $rs->first;
+ print $album->title;
-DBIx::Class provides a few different ways to retrieve data from your database.
-The simplest looks something like this:
+You can loop over the albums and update each one:
- $album = MyApp::DB::Album->search( artist => 'Santana' );
+ while (my $album = $rs->next) {
+ print $album->artist . ' - ' . $album->title;
+ $album->year(2001);
+ $album->update;
+ }
-note that all the search methods return a L<DBIx::Class::ResultSet> object
-in scalar context or a list containing all the records in list context.
+Or, you can update them all at once:
-We also provide a handy shortcut for doing a "like" search:
+ $rs->update({ year => 2001 });
- $album = MyApp::DB::Album->search_like( artist => 'Jimi%');
+In list context, the C<search> method returns all of the matching rows:
-Or you can provide your own handmade WHERE clause, like
-
- $album = MyApp::DB::Album->search_literal('artist=?','Peter Frampton');
+ # 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;
+ }
-The other way to provide more complex queries, is to provide a
-L<SQL::Abstract> construct to search:
+We also provide a handy shortcut for doing a C<LIKE> search:
- $album = MyApp::DB::Album->search({
- artist => { '!=', 'Janis Joplin' },
- year => { '<' => 1980 },
- id => [ 1, 14, 15, 65, 43 ]
+ # 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 );
+
+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 ] }
});
-The search can also be modifyed by passing another hash with attributes:
+This results in something like the following C<WHERE> clause:
+
+ 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 @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 is a problem with slow performance of certain DBIx::Class operations in
+perl-5.8.8-10 and later on RedHat and related systems, due to a bad backport of
+a "use overload" related bug. The problem is in the Perl binary itself, not in
+DBIx::Class. If your system has this problem, you will see a warning on
+startup, with some options as to what to do about it.
+
+=head1 SEE ALSO
+
+=over 4
- $album = MyApp::DB::Album->search(
- { artist => 'Bob Marley' },
- { page => 1, rows => 2, order_by => 'year' }
- );
+=item * L<DBIx::Class::Manual::Cookbook>
-For a complete overview over the available attributes, see
-L<DBIx::Class::ResultSet>
+=back
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff