=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::Schema::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
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_classes() method. You can specify which
+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:
# load My::Schema::Album and My::Schema::Artist
__PACKAGE__->load_components(qw/ PK::Auto Core /);
-C<PK::Auto> is supported for many databases; see
-L<DBIx::Class::Storage::DBI> for more information.
+C<PK::Auto> is supported for many databases; see L<DBIx::Class::Storage::DBI>
+for more information.
Set the table for 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 such as:
+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',
}
);
-Most of this data isn't yet used directly by DBIx::Class, 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.
+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.
__PACKAGE__->set_primary_key( qw/ albumid artistid / );
-Define relationships that the class has with any other classes by 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 tables foreign key in one of their columns:
+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__->has_many('albums', 'My::Schema::Artist', 'album_id');
-More information about the various types of relationships available, and
-how you can design your own, can be found in L<DBIx::Class::Relationship>.
-
+See L<DBIx::Class::Relationship> for more information about the various types of
+available relationships and how you can design your own.
=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:
+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__->load_from_connection(
- connect_info = [ 'dbi:SQLite:/home/me/myapp/my.db' ]
- );
+ __PACKAGE__->loader_options( relationships => 1 );
1;
-This should be equivalent to the manual setup in the section above.
-L<DBIx::Class::Schema::Loader> takes lots of other options. For more
-information, consult its documentation.
-
-=head2 Connecting
+The actual autoloading process will occur when you create a connected instance
+of your schema below.
-L<DBIx::Class::Schema::Loader> already contains the connection info for the
-database, so to get started all you need to do is create an instance of your
-class:
+See the L<DBIx::Class::Schema::Loader> documentation for more information on its
+many options.
- my $schema = My::Schema->new();
+=head2 Connecting
-To connect to your manually created Schema, you also need to provide the
-connection details:
+To connect to your Schema, you need to provide the 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:
+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 connnections for you. If you
-use multiple connections, you need to do this manually.
+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 pass them to your schema after the connect:
+To execute some sql statements on every connect you can add them as an option in
+a special fifth argument to connect:
- $schema->storage->on_connect_do(\@on_connect_sql_statments);
+ 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 ->resultset method.
+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:
+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');
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 call C<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 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<My::Schema::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::Album> that can be used to access the data
+in the new record:
my $new_album = $schema->resultset('Album')->create({
title => 'Wish You Were Here',
$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 retrieving them first, by calling
-delete directly on a ResultSet object.
+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;
=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 = $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;
$rs->update({ year => 2001 });
-For more information on what you can do with a
-L<DBIx::Class::ResultSet>, see L<DBIx::Class::ResultSet/METHODS>.
-
-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 = $schema->resultset('Album')->search(
# 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, 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 = $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 = $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:
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
=item * L<DBIx::Class::Manual::Cookbook>
-=item * L<DBIx::Class::Manual::FAQ>
-
=back
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff