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 (CLIFF NOTES)
+
+Here are a few simple tips that will help you get your bearings with
+L<DBIC|DBIx::Class>.
+
+=head2 Tables become Result classes
+
+L<DBIC|DBIx::Class> needs to know what your Table structure looks like. You
+do that by defining L<Result classes|DBIx::Class::Manual::ResultClass>. Each
+Result class defines one Table, which defines the Columns it has, any
+L<Relationships|DBIx::Class::Relationship> it has to other tables, and much more.
+
+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
+
+Let's say we defined a L<Result class|DBIx::Class::Manual::ResultClass> (called
+C<MyApp::Schema::Result::Artist>) for an C<album> table with three columns:
+C<albumid>, C<artist>, and C<title>. Any time we want to query this table, we'll
+be creating a L<ResultSet|DBIx::Class::ResultSet> from its
+L<Schema|DBIx::Class::Schema>. For example, the results of:
+
+ SELECT albumid, artist, title FROM album;
+
+Would be represented like so:
+
+ my $rs = $schema->resultset('Album')->search(undef, {
+ columns => [qw{ albumid artist title }]
+ });
+
+L<DBIC|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, like this:
+
+ my $rs = $schema->resultset('Album')->search(undef, {
+ columns => ['title'],
+ group_by => ['title'],
+ });
+
+The important thing to understand:
+
+ Instead of writing SQL queries manually, you ask a ResultSet object to
+ generate them.
+
+=head2 Search results are returned as "Rows"
+
+Rows of the search from the database are blessed into
+L<Result objects|DBIx::Class::Manual::ResultClass>. This might seem conflicting,
+but this is because a Result class is supposed to be customizable "toolset" for
+both result management and table definition.
+
+The important thing to understand:
+
+ When -defining- a Result class, the purpose of the class is to:
+ * Define the table, columns, and constraints
+ * Define relationships to other tables
+
+ When -using- a Result object, the purpose of the object is to:
+ * Read data from a result (like a row)
+ * Perform CRUD operations, based on that data
+ * "Inflate" columns
+ * Use custom methods defined in the class by you
+
+=head2 Search is like "prepare"
+
+L<DBIC|DBIx::Class> tends to wait until it absolutely must fetch information from the
+database. If you are returning a L<ResultSet|DBIx::Class::ResultSet>, the
+query won't execute until you use a method that wants to access the data, such
+as C<next> or C<first>.
+
+ # Does not run any SQL statements yet
+ my $rs = $schema->resultset('Album')->search(undef, {
+ columns => [qw{ albumid artist title }]
+ });
+
+ # Will trigger the SQL query once and loop through the results
+ while (my $result = $rs->next) {
+ my $artist = $result->artist;
+ ...
+ }
+
+=head1 SETTING UP DBIx::Class
+
+Let's look at how you can set and use your first native L<DBIC|DBIx::Class> tree.
+
+=head2 Which deployment method to take
+
+There are a few different ways to create your L<DBIC|DBIx::Class> tree. Which
+recommended method to take depends on how your database currently exists:
+
+ * If you are creating a brand new database, set up the tree manually, and then
+ create the tables via $schema->deploy (or another deployment tool).
+ * If the database already exists, use DBIx::Class::Schema::Loader or another
+ schema builder.
+
+Since L<DBIC|DBIx::Class> first came into the scene, there have been a number of
+useful deployment tools (schema builders) that ease the process (from oldest to
+newest):
+
+=over
+
+=item *
+
+L<DBIx::Class::Schema::Loader> (existing DB only)
+
+=item *
+
+L<DBIx::Class::DeploymentHandler> (new or existing DB)
+
+=item *
+
+L<DBIx::Class::Migration> (new or existing DB)
+
+=back
+
+This document only covers the manual method and L<DBICSL|/Using
+DBIx::Class::Schema::Loader>. However, users with complex schemas might want
+to check out the latest deployment tech to make life easier.
=head2 Setting it up manually
-First, you'll need a base class. It should inherit from DBIx::Class
-like this:
+=head3 Schema
+
+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 C<result_source> ("table", "model") classes, which
+we will define later, using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
+method:
+
+ # load My::Schema::Result::* and their resultset classes
+ __PACKAGE__->load_namespaces();
+
+By default, this loads all the L<Result classes|DBIx::Class::Manual::ResultClass>
+in the C<My::Schema::Result::> namespace, and also any ResultSet classes in the
+C<My::Schema::ResultSet::> namespace. (If missing, the ResultSets are
+defaulted to be L<DBIx::Class::ResultSet> objects.) You can change the Result
+and ResultSet namespaces by using options to the
+L<load_namespaces|DBIx::Class::Schema/load_namespaces> call.
+
+It is also possible to do the same things manually by calling
+L<load_classes|DBIx::Class::Schema/load_classes> for the
+L<Result classes|DBIx::Class::Manual::ResultClass> and
+defining in those classes any required ResultSet classes.
+
+=head3 Result class
+
+=head4 Header
+
+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
+L<load_components|Class::C3::Componentised/load_components( @comps )> method,
+and provide component configuration if required. For example, if you want
+automatic row ordering:
+
+ __PACKAGE__->load_components(qw/ Ordered /);
+ __PACKAGE__->position_column('rank');
- package MyApp::DB
- use base qw/DBIx::Class/;
+(See L<DBIx::Class::Ordered> for more information.)
-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.
+Set the table for your class:
- __PACKAGE__->load_components(qw/Core DB/);
+ __PACKAGE__->table('album');
-If you want serial/auto-incremental primary keys, you'll need to add
-the apropriate component for your db as well, for example
+=head4 Columns
- __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 user/pass/dbi
-attribute hash as well as the dsn.
+ __PACKAGE__->add_columns(
+ albumid => {
+ accessor => 'album',
+ data_type => 'integer',
+ size => 16,
+ is_auto_increment => 1,
+ },
+ artist => {
+ data_type => 'integer',
+ size => 16,
+ },
+ title => {
+ data_type => 'varchar',
+ size => 256,
+ is_nullable => 1,
+ },
+ rank => {
+ data_type => 'integer',
+ size => 16,
+ default_value => 0,
+ },
+ );
-With that out of the way, we can define our first table class:
+L<DBIC|DBIx::Class> doesn't directly use most of this data, but various
+related modules, such as L<HTML::FormHandler::Model::DBIC>, 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::Frob
+See L<DBIx::Class::ResultSource/add_columns> for more details of the possible column
+attributes.
- use base qw/MyApp::DB/;
+Accessors are created for each column automatically, so C<My::Schema::Result::Album>
+will have C<albumid> (or C<album>, when using the accessor shown above), C<artist>
+and C<title> methods.
-Then we specify which table it uses,
+=head4 Primary Key
- __PACKAGE__->table('frob');
+Define a primary key for your class:
-and specify which columns it has.
+ __PACKAGE__->set_primary_key('albumid');
- __PACKAGE__->add_columns(qw/id foo bar/);
+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:
+See also L</The Significance and Importance of Primary Keys>.
- __PACKAGE__->set_primary_key('id');
+=head4 Relationships
-If you have multiple primary keys, just pass a list instead.
+Define this class' relationships with other classes to make predefined accessors
+for your L<Result class|DBIx::Class::Manual::ResultClass>. Use either
+L<belongs_to|DBIx::Class::Relationship/belongs_to> to describe columns which
+contain an ID of another Table, or
+L<has_many|DBIx::Class::Relationship/has_many> to fetch objects that contain this
+Table's foreign key:
-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>.
+ # in My::Schema::Result::Artist
+ __PACKAGE__->has_many('albums', 'My::Schema::Result::Album', 'artist');
-=head2 Using L<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.
-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:
+=head2 Using DBIx::Class::Schema::Loader
- package MyApp::DB;
-
- use DBIx::Class::Loader;
+L<DBICSL|DBIx::Class::Schema::Loader> is an external module, and not part
+of the L<DBIC|DBIx::Class> distribution. It inspects your database, and
+automatically creates classes for all the tables in your schema.
- my $loader=DBIx::Class::Loader->new(
- dsn => 'dbi:SQLite:/home/me/myapp/my.db',
- namespace => 'MyApp::DB');
- 1;
+The simplest way to use it is via the L<dbicdump> script from the
+L<DBIx::Class::Schema::Loader> distribution. For example:
-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.
+ $ dbicdump -o dump_directory=./lib \
+ -o components='["InflateColumn::DateTime"]' \
+ MyApp::Schema dbi:mysql:mydb user pass
-=head2 Basic Usage
+If you have a mixed-case database, use the C<preserve_case> option, e.g.:
-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:
+ $ dbicdump -o dump_directory=./lib -o preserve_case=1 \
+ -o components='["InflateColumn::DateTime"]' \
+ MyApp::Schema dbi:mysql:mydb user pass
- my $frob=MyApp::DB::Frob->find(14);
+If you are using L<Catalyst>, then you can use the helper that comes with
+L<Catalyst::Model::DBIC::Schema>:
-This will run a select with id=14 in the WHERE clause, and return an instance
-of MyApp::DB::Frob that represents this row. Once you have that row, you can
-access and update columns
+ $ script/myapp_create.pl model MyDB DBIC::Schema MyDB::Schema \
+ create=static moniker_map='{ foo => "FOO" }' dbi:SQLite:./myapp.db \
+ on_connect_do='PRAGMA foreign_keys=ON' quote_char='"'
- my $val=$frob->bar;
- $frob->bar(14);
+See L<Catalyst::Helper::Model::DBIC::Schema> for more information on this
+helper.
-or if you prefer, you can use the set_column/get_column accessors instead
-of the autogenerated accessors based on your column names.
+See the L<DBIx::Class::Schema::Loader> and L<DBIx::Class::Schema::Loader::Base>
+documentation for more information on the many loader options.
-Just like with L<Class::DBI>, you do an 'update' to commit your changes
-to the database:
+=head2 Connecting
- $frob->update;
+To connect to your Schema, you need to provide the connection details or a
+database handle.
-If needed, you can drop your local changes instead like this:
+=head3 Via connection details
- $frob->discard_changes if $frob->is_changed;
+The arguments are the same as for L<DBI/connect>:
-As you can see, is_changed allows you to check if there are local changes to
+ 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,
+ $attrs,
+ { on_connect_do => \@on_connect_sql_statments }
+ );
+
+See L<DBIx::Class::Storage::DBI/connect_info> for more information about
+this and other special C<connect>-time options.
+
+=head3 Via a database handle
+
+The supplied coderef is expected to return a single connected database handle
+(e.g. a L<DBI> C<$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::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::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:
+
+ $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):
+
+ $album->update;
+
+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.
-=head2 Adding and removing rows.
+=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::Result::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',
+ artist => 'Pink Floyd'
+ });
+
+Now you can add data to the new record:
+
+ $new_album->label('Capitol');
+ $new_album->year('1975');
+ $new_album->update;
-To make a new row, and put it into the database, you can use the 'create'
-method from L<DBIx::Class::Row>
+Likewise, you can remove it from the database:
- my $new_thingie=MyApp::DB::Frob->create({
- foo=>'homer',
- bar=>'bart' });
+ $new_album->delete;
-likewise, you can remove if from the database like this:
+You can also remove records without retrieving them first, by calling delete
+directly on a ResultSet object.
- $new_thingie->delete();
+ # Delete all of Falco's albums
+ $schema->resultset('Album')->search({ artist => 'Falco' })->delete;
-or even without retrieving first. This operation takes the same kind of
-arguments as a search.
+=head2 Finding your objects
- MyApp::DB::Frob->delete({foo=>'bart'});
+L<DBIC|DBIx::Class> provides a few different ways to retrieve data from your
+database. Here's one example:
-=head2 Finding your objects.
+ # Find all of Santana's albums
+ my $rs = $schema->resultset('Album')->search({ artist => 'Santana' });
-DBIx::Class provides a few different ways to retrieve data from your database.
-The simplest looks something like this:
+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:
- $rs=MyApp::DB::Frob->search(foo=>'bart');
+ my $album = $rs->first;
+ print $album->title;
-note that all the search methods return a recordset in scalar context or
-a list containing all the elements in list context.
+You can loop over the albums and update each one:
-We also provide a handy shortcut for doing a like search:
+ while (my $album = $rs->next) {
+ print $album->artist . ' - ' . $album->title;
+ $album->year(2001);
+ $album->update;
+ }
- $rs=MyApp::DB::Frob->search_like(foo=>'bar%');
+Or, you can update them all at once:
-Or you can provide your own handmade WHERE clause, like
-
- $rs=MyApp::DB::Frob->search_literal('foo=?','bart');
+ $rs->update({ year => 2001 });
-The other way to provide more complex queries, is to provide a
-L<SQL::Abstract> construct to search:
+In list context, the C<search> method returns all of the matching rows:
- $rs=MyApp::DB::Frob->search({
- bar=>{'>' => 10 },
- foo=>{'!=','bart'},
- id => [1,14,15,65,43]
+ # 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:
+
+ # 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 => { -desc => 'year' } }
+ );
+
+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 The Significance and Importance of Primary Keys
+
+The concept of a L<primary key|DBIx::Class::ResultSource/set_primary_key> in
+L<DBIC|DBIx::Class> warrants special discussion. The formal definition (which somewhat
+resembles that of a classic RDBMS) is I<a unique constraint that is least
+likely to change after initial row creation>. However, this is where the
+similarity ends. Any time you call a CRUD operation on a row (e.g.
+L<delete|DBIx::Class::Row/delete>,
+L<update|DBIx::Class::Row/update>,
+L<discard_changes|DBIx::Class::Row/discard_changes>,
+etc.), L<DBIC|DBIx::Class> will use the values of of the
+L<primary key|DBIx::Class::ResultSource/set_primary_key> columns to populate
+the C<WHERE> clause necessary to accomplish the operation. This is why it is
+important to declare a L<primary key|DBIx::Class::ResultSource/set_primary_key>
+on all your result sources B<even if the underlying RDBMS does not have one>.
+In a pinch, one can always declare each row identifiable by all its columns:
+
+ __PACKAGE__->set_primary_key(__PACKAGE__->columns);
+
+Note that L<DBIC|DBIx::Class> is smart enough to store a copy of the PK values before
+any row-object changes take place, so even if you change the values of PK
+columns, the C<WHERE> clause will remain correct.
+
+If you elect not to declare a C<primary key>, L<DBIC|DBIx::Class> will behave correctly
+by throwing exceptions on any row operation that relies on unique identifiable
+rows. If you inherited datasets with multiple identical rows in them, you can
+still operate with such sets provided you only utilize
+L<DBIx::Class::ResultSet> CRUD methods:
+L<search|DBIx::Class::ResultSet/search>,
+L<update|DBIx::Class::ResultSet/update>,
+L<delete|DBIx::Class::ResultSet/delete>
+
+For example, the following would not work (assuming C<People> does not have
+a declared PK):
+
+ my $row = $schema->resultset('People')
+ ->search({ last_name => 'Dantes' })
+ ->next;
+ $row->update({ children => 2 }); # <-- exception thrown because $row isn't
+ # necessarily unique
+
+So, instead the following should be done:
+
+ $schema->resultset('People')
+ ->search({ last_name => 'Dantes' })
+ ->update({ children => 2 }); # <-- update's ALL Dantes to have children of 2
+
+=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>
- $rs=MyApp::DB::Frob->search( {foo=>'bart'},
- { page=>1, rows=>2, order_by=>'bar' } );
+=item * L<DBIx::Class::Manual::ResultClass>
-For a complete overview over the available attributes, see
-L<DBIx::Class::ResultSet>
+=back
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff