3 DBIx::Class::Manual::Intro - Introduction to DBIx::Class
7 You're bored with SQL, and want a native Perl interface for your database? Or
8 you've been doing this for a while with L<Class::DBI>, and think there's a
9 better way? You've come to the right place.
11 =head1 THE DBIx::Class WAY
13 Here are a few simple tips that will help you get your bearings with
16 =head2 Tables become Result classes
18 DBIx::Class needs to know what your Table structure looks like. You
19 do that by defining Result classes. Result classes are defined by
20 calling methods proxied to L<DBIx::Class::ResultSource>. Each Result
21 class defines one Table, which defines the Columns it has, along with
22 any Relationships it has to other tables. (And oh, so much more
23 besides) The important thing to understand:
25 A Result class == Table
27 (most of the time, but just bear with my simplification)
29 =head2 It's all about the ResultSet
31 So, we've got some ResultSources defined. Now, we want to actually use those
32 definitions to help us translate the queries we need into handy perl objects!
34 Let's say we defined a ResultSource for an "album" table with three columns:
35 "albumid", "artist", and "title". Any time we want to query this table, we'll
36 be creating a L<DBIx::Class::ResultSet> from its ResultSource. For example, the
39 SELECT albumid, artist, title FROM album;
41 Would be retrieved by creating a ResultSet object from the album table's
42 ResultSource, likely by using the "search" method.
44 DBIx::Class doesn't limit you to creating only simple ResultSets -- if you
45 wanted to do something like:
47 SELECT title FROM album GROUP BY title;
49 You could easily achieve it.
51 The important thing to understand:
53 Any time you would reach for a SQL query in DBI, you are
54 creating a DBIx::Class::ResultSet.
56 =head2 Search is like "prepare"
58 DBIx::Class tends to wait until it absolutely must fetch information from the
59 database. If you are returning a ResultSet, the query won't execute until you
60 use a method that wants to access the data. (Such as "next", or "first")
62 The important thing to understand:
64 Setting up a ResultSet does not execute the query; retrieving
67 =head2 Search results are returned as Rows
69 Rows of the search from the database are blessed into
70 L<DBIx::Class::Row> objects.
72 =head1 SETTING UP DBIx::Class
74 Let's look at how you can set and use your first native L<DBIx::Class> tree.
76 First we'll see how you can set up your classes yourself. If you want them to
77 be auto-discovered, just skip to the next section, which shows you how to use
78 L<DBIx::Class::Schema::Loader>.
80 =head2 Setting it up manually
82 First, you should create your base schema class, which inherits from
83 L<DBIx::Class::Schema>:
86 use base qw/DBIx::Class::Schema/;
88 In this class you load your result_source ("table", "model") classes, which we
89 will define later, using the load_classes() method. You can specify which
90 classes to load manually:
92 # load My::Schema::Album and My::Schema::Artist
93 __PACKAGE__->load_classes(qw/ Album Artist /);
95 Or load classes by namespace:
97 # load My::Schema::Album, My::Schema::Artist and My::OtherSchema::LinerNotes
98 __PACKAGE__->load_classes(
100 'My::Schema' => [qw/ Album Artist /],
101 'My::OtherSchema' => [qw/ LinerNotes /]
105 Or let your schema class load all classes in its namespace automatically:
108 __PACKAGE__->load_classes();
110 Next, create each of the classes you want to load as specified above:
112 package My::Schema::Album;
113 use base qw/DBIx::Class/;
115 Load any components required by each class with the load_components() method.
116 This should consist of "Core" plus any additional components you want to use.
117 For example, if you want serial/auto-incrementing primary keys:
119 __PACKAGE__->load_components(qw/ PK::Auto Core /);
121 C<PK::Auto> is supported for many databases; see L<DBIx::Class::Storage::DBI>
122 for more information.
124 Set the table for your class:
126 __PACKAGE__->table('album');
128 Add columns to your class:
130 __PACKAGE__->add_columns(qw/ albumid artist title /);
132 Each column can also be set up with its own accessor, data_type and other pieces
133 of information that it may be useful to have -- just pass C<add_columns> a hash:
135 __PACKAGE__->add_columns(albumid =>
136 { accessor => 'album',
137 data_type => 'integer',
140 is_auto_increment => 1,
144 { data_type => 'integer',
147 is_auto_increment => 0,
151 { data_type => 'varchar',
154 is_auto_increment => 0,
159 DBIx::Class doesn't directly use most of this data yet, but various related
160 modules such as L<DBIx::Class::WebForm> make use of it. Also it allows you to
161 create your database tables from your Schema, instead of the other way around.
162 See L<SQL::Translator> for details.
164 See L<DBIx::Class::ResultSource> for more details of the possible column
167 Accessors are created for each column automatically, so My::Schema::Album will
168 have albumid() (or album(), when using the accessor), artist() and title()
171 Define a primary key for your class:
173 __PACKAGE__->set_primary_key('albumid');
175 If you have a multi-column primary key, just pass a list instead:
177 __PACKAGE__->set_primary_key( qw/ albumid artistid / );
179 Define this class' relationships with other classes using either C<belongs_to>
180 to describe a column which contains an ID of another Table, or C<has_many> to
181 make a predefined accessor for fetching objects that contain this Table's
184 __PACKAGE__->has_many('albums', 'My::Schema::Artist', 'album_id');
186 See L<DBIx::Class::Relationship> for more information about the various types of
187 available relationships and how you can design your own.
189 =head2 Using L<DBIx::Class::Schema::Loader>
191 This is an external module, and not part of the L<DBIx::Class> distribution.
192 Like L<Class::DBI::Loader>, it inspects your database, and automatically creates
193 classes for all the tables in your database. Here's a simple setup:
196 use base qw/DBIx::Class::Schema::Loader/;
198 __PACKAGE__->loader_options( relationships => 1 );
202 The actual autoloading process will occur when you create a connected instance
203 of your schema below.
205 See the L<DBIx::Class::Schema::Loader> documentation for more information on its
210 To connect to your Schema, you need to provide the connection details. The
211 arguments are the same as for L<DBI/connect>:
213 my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db');
215 You can create as many different schema instances as you need. So if you have a
216 second database you want to access:
218 my $other_schema = My::Schema->connect( $dsn, $user, $password, $attrs );
220 Note that L<DBIx::Class::Schema> does not cache connections for you. If you use
221 multiple connections, you need to do this manually.
223 To execute some sql statements on every connect you can add them as an option in
224 a special fifth argument to connect:
226 my $another_schema = My::Schema->connect(
231 { on_connect_do => \@on_connect_sql_statments }
234 See L<DBIx::Class::Schema::Storage::DBI/connect_info> for more information about
235 this and other special C<connect>-time options.
239 Once you've defined the basic classes, either manually or using
240 L<DBIx::Class::Schema::Loader>, you can start interacting with your database.
242 To access your database using your $schema object, you can fetch a
243 L<DBIx::Class::Manual::Glossary/"ResultSet"> representing each of your tables by
244 calling the C<resultset> method.
246 The simplest way to get a record is by primary key:
248 my $album = $schema->resultset('Album')->find(14);
250 This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause, and
251 return an instance of C<My::Schema::Album> that represents this row. Once you
252 have that row, you can access and update columns:
254 $album->title('Physical Graffiti');
255 my $title = $album->title; # $title holds 'Physical Graffiti'
257 If you prefer, you can use the C<set_column> and C<get_column> accessors
260 $album->set_column('title', 'Presence');
261 $title = $album->get_column('title');
263 Just like with L<Class::DBI>, you call C<update> to commit your changes to the
268 If needed, you can throw away your local changes:
270 $album->discard_changes if $album->is_changed;
272 As you can see, C<is_changed> allows you to check if there are local changes to
275 =head2 Adding and removing rows
277 To create a new record in the database, you can use the C<create> method. It
278 returns an instance of C<My::Schema::Album> that can be used to access the data
281 my $new_album = $schema->resultset('Album')->create({
282 title => 'Wish You Were Here',
283 artist => 'Pink Floyd'
286 Now you can add data to the new record:
288 $new_album->label('Capitol');
289 $new_album->year('1975');
292 Likewise, you can remove it from the database:
296 You can also remove records without retrieving them first, by calling delete
297 directly on a ResultSet object.
299 # Delete all of Falco's albums
300 $schema->resultset('Album')->search({ artist => 'Falco' })->delete;
302 =head2 Finding your objects
304 L<DBIx::Class> provides a few different ways to retrieve data from your
305 database. Here's one example:
307 # Find all of Santana's albums
308 my $rs = $schema->resultset('Album')->search({ artist => 'Santana' });
310 In scalar context, as above, C<search> returns a L<DBIx::Class::ResultSet>
311 object. It can be used to peek at the first album returned by the database:
313 my $album = $rs->first;
316 You can loop over the albums and update each one:
318 while (my $album = $rs->next) {
319 print $album->artist . ' - ' . $album->title;
324 Or, you can update them all at once:
326 $rs->update({ year => 2001 });
328 In list context, the C<search> method returns all of the matching rows:
330 # Fetch immediately all of Carlos Santana's albums
331 my @albums = $schema->resultset('Album')->search(
332 { artist => 'Carlos Santana' }
334 foreach my $album (@albums) {
335 print $album->artist . ' - ' . $album->title;
338 We also provide a handy shortcut for doing a C<LIKE> search:
340 # Find albums whose artist starts with 'Jimi'
341 my $rs = $schema->resultset('Album')->search_like({ artist => 'Jimi%' });
343 Or you can provide your own C<WHERE> clause:
345 # Find Peter Frampton albums from the year 1986
346 my $where = 'artist = ? AND year = ?';
347 my @bind = ( 'Peter Frampton', 1986 );
348 my $rs = $schema->resultset('Album')->search_literal( $where, @bind );
350 The preferred way to generate complex queries is to provide a L<SQL::Abstract>
351 construct to C<search>:
353 my $rs = $schema->resultset('Album')->search({
354 artist => { '!=', 'Janis Joplin' },
355 year => { '<' => 1980 },
356 albumid => { '-in' => [ 1, 14, 15, 65, 43 ] }
359 This results in something like the following C<WHERE> clause:
361 WHERE artist != 'Janis Joplin'
363 AND albumid IN (1, 14, 15, 65, 43)
365 For more examples of complex queries, see L<DBIx::Class::Manual::Cookbook>.
367 The search can also be modified by passing another hash with
370 my @albums = My::Schema->resultset('Album')->search(
371 { artist => 'Bob Marley' },
372 { rows => 2, order_by => 'year DESC' }
375 C<@albums> then holds the two most recent Bob Marley albums.
377 For more information on what you can do with a L<DBIx::Class::ResultSet>, see
378 L<DBIx::Class::ResultSet/METHODS>.
380 For a complete overview of the available attributes, see
381 L<DBIx::Class::ResultSet/ATTRIBUTES>.
385 =head2 Problems on RHEL5/CentOS5
387 There is a problem with slow performance of certain DBIx::Class operations in
388 perl-5.8.8-10 and later on RedHat and related systems, due to a bad backport of
389 a "use overload" related bug. The problem is in the Perl binary itself, not in
390 DBIx::Class. If your system has this problem, you will see a warning on
391 startup, with some options as to what to do about it.
397 =item * L<DBIx::Class::Manual::Cookbook>