X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FManual%2FIntro.pod;h=974efe5c226290b6ef98116ef60d217e7bc53bb5;hb=11736b4c186bbc10c80f13fdb1eca80b1ff75711;hp=60034898dba0c24a7b7c3b7fc717913c6c081e36;hpb=40dbc10813c6f5bd0a91a08b5e00d1027c390c0c;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Manual/Intro.pod b/lib/DBIx/Class/Manual/Intro.pod
index 6003489..974efe5 100644
--- a/lib/DBIx/Class/Manual/Intro.pod
+++ b/lib/DBIx/Class/Manual/Intro.pod
@@ -4,202 +4,391 @@ DBIx::Class::Manual::Intro - Introduction to DBIx::Class
 
 =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
+
+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 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
+classes to load manually: 
+
+  # load My::Schema::Album and My::Schema::Artist
+  __PACKAGE__->load_classes(qw/ Album Artist /);
+
+Or load classes by namespace:
+
+  # load My::Schema::Album, My::Schema::Artist and My::OtherSchema::LinerNotes
+  __PACKAGE__->load_classes(
+    {
+      'My::Schema' => [qw/ Album Artist /],
+      'My::OtherSchema' => [qw/ LinerNotes /]
+    }
+  );
+
+Or let your schema class load all classes in its namespace automatically:
+
+   # load My::Schema::*
+  __PACKAGE__->load_classes();
+
+Next, create each of the classes you want to load as specified above:
+
+  package My::Schema::Album;
+  use base qw/DBIx::Class/;
 
-    package MyApp::DB;
-    use base qw/DBIx::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:
 
-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 C<DB> in this introduction, since it involves less magic.
-L<Schema> is mostly useful if you want to use multiple database
-connections.
+  __PACKAGE__->load_components(qw/ PK::Auto Core /);
 
-    __PACKAGE__->load_components(qw/Core DB/);
+C<PK::Auto> is supported for many databases; see L<DBIx::Class::Storage::DBI>
+for more information.
 
-If you want serial/auto-incremental primary keys, you'll need to add
-the apropriate component for your db as well, for example. The
-L<DBIx::Class::PK::Auto> modules help L<DBIx::Class> keep up with
-newly generated keys in auto increment database fields.
+Set the table for your class:
 
-    __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+  __PACKAGE__->table('album');
 
-Once you've loaded the components, it's time to  set up your connection:
+Add columns to your class:
 
-    __PACKAGE__->connection('dbi:SQLite:/home/me/myapp/my.db');
+  __PACKAGE__->add_columns(qw/ albumid artist title /);
 
-This method is similar to the normal L<DBI>, and can take username,
-password, and L<DBI> attribute hash as well as the DSN.
+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:
 
-With that out of the way, we can define our first table class:
+  __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 => '',
+                            }
+                         );
 
-    package MyApp::DB::Album;
-    use base qw/MyApp::DB/;
+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.
 
-Then we specify which table it uses,
+See L<DBIx::Class::ResultSource> for more details of the possible column
+attributes.
 
-    __PACKAGE__->table('album');
+Accessors are created for each column automatically, so My::Schema::Album will
+have albumid() (or album(), when using the accessor), artist() and title()
+methods.
 
-and specify which columns it has.
+Define a primary key for your class:
 
-    __PACKAGE__->add_columns(qw/albumID artist title label year/);
+  __PACKAGE__->set_primary_key('albumid');
 
-This will automatically create accessors for each of the columns, so
-that you can read/update the values in rows you've retrieved.
+If you have a multi-column primary key, just pass a list instead:
 
-Also, you need to tell it which column is the primary key:
+  __PACKAGE__->set_primary_key( qw/ albumid artistid / );
 
-    __PACKAGE__->set_primary_key('albumID');
+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:
 
-If you have multiple primary keys, just pass a list instead.
+  __PACKAGE__->has_many('albums', 'My::Schema::Artist', 'album_id');
 
-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>.
+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::Loader>
+=head2 Using L<DBIx::Class::Schema::Loader>
 
-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:
+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 MyApp::DB;
-    use DBIx::Class::Loader;
+  package My::Schema;
+  use base qw/DBIx::Class::Schema::Loader/;
 
-    my $loader = DBIx::Class::Loader->new(
-        dsn       => 'dbi:SQLite:/home/me/myapp/my.db',
-        namespace => 'MyApp::DB'
-    );
+  __PACKAGE__->loader_options( relationships => 1 );
 
-    1;
+  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 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.  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.
 
 =head2 Basic usage
 
-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:
+Once you've defined the basic classes, either manually or using
+L<DBIx::Class::Schema::Loader>, you can start interacting with your database.
 
-    my $albumID = 14;
-    my $album   = MyApp::DB::Album->find($albumID);
+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.
 
-This will run a select with C<albumID = 14> in the C<WHERE> clause,
-and return an instance of C<MyApp::DB::Artist> that represents this
-row. Once you have that row, you can access and update columns:
+The simplest way to get a record is by primary key:
 
-    $album->title('Physical Graffiti');
-    my $title = $album->title; # $title holds 'Physical Graffiti'
+  my $album = $schema->resultset('Album')->find(14);
 
-If you prefer, you can use the C<set_column> and C<get_column>
-accessors instead:
+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->set_column('title', 'Presence');
-    $title = $album->get_column('title');
+  $album->title('Physical Graffiti');
+  my $title = $album->title; # $title holds 'Physical Graffiti'
 
-Just like with L<Class::DBI>, you do an C<update> to commit your
-changes to the database:
+If you prefer, you can use the C<set_column> and C<get_column> accessors
+instead:
 
-    $album->update;
+  $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:
 
-If needed, you can drop your local changes instead like this:
+  $album->update;
 
-    $album->discard_changes if $album->is_changed;
+If needed, you can throw away your local changes:
 
-As you can see, C<is_changed> allows you to check if there are local
-changes to your object.
+  $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
 
-To create a new record in the database, you can use the C<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:
 
-    my $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->label('Capitol');
+  $new_album->year('1975');
+  $new_album->update;
 
-Likewise, you can remove if from the database like this:
+Likewise, you can remove it from the database:
 
-    $new_album->delete;
+  $new_album->delete;
 
-or even without 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.
 
-    MyApp::DB::Album->delete({ artist => 'Falco' });
+  # 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.  The simplest looks something like this:
+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:
 
-    my $album = MyApp::DB::Album->search( artist => 'Santana' );
+  my $album = $rs->first;
+  print $album->title;
 
-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.
+You can loop over the albums and update each one:
+
+  while (my $album = $rs->next) {
+    print $album->artist . ' - ' . $album->title;
+    $album->year(2001);
+    $album->update;
+  }
+
+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:
+
+  # 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:
 
-    my $album = MyApp::DB::Album->search_like( artist => 'Jimi%' );
+  # 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 );
 
-Or you can provide your own handmade C<WHERE> clause, like:
-  
-    my $album = MyApp::DB::Album->search_literal( 'artist = ?', 'Peter Frampton' );
+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 => { '-in' => [ 1, 14, 15, 65, 43 ] }
+  });
 
-    my $album = MyApp::DB::Album->search({
-        artist => { '!=', 'Janis Joplin' },
-        year   => { '<' => 1980 },
-        id     => [ 1, 14, 15, 65, 43 ]
-    });
+This results in something like the following C<WHERE> clause:
 
-For more examples of complex searches, see
-L<DBIx::Class::Manual::Cookbook>.
+  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 $album = MyApp::DB::Album->search( 
-        { artist => 'Bob Marley' },
-        { page => 1, rows => 2, order_by => 'year' }
-    );
+  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
 
 =item * L<DBIx::Class::Manual::Cookbook>
 
-=item * L<DBIx::Class::Manual::FAQ>
-
 =back
 
 =cut