X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FManual%2FIntro.pod;h=5c7f7e5809c9d76dd87d012f510472681b614198;hb=5f550837848772810f7ebe6067e1e50150560d39;hp=928a5654f750626c61b8083abb412e834afe0b4d;hpb=d56c319181b46e4f80d301d27d2f80e49751b460;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Manual/Intro.pod b/lib/DBIx/Class/Manual/Intro.pod
index 928a565..5c7f7e5 100644
--- a/lib/DBIx/Class/Manual/Intro.pod
+++ b/lib/DBIx/Class/Manual/Intro.pod
@@ -74,7 +74,8 @@ L<DBIx::Class::Row> objects.
 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
+be auto-discovered, just skip to the L<next section|/Using
+DBIx::Class::Schema::Loader>, which shows you how to use
 L<DBIx::Class::Schema::Loader>.
 
 =head2 Setting it up manually
@@ -105,13 +106,18 @@ required resultset classes.
 Next, create each of the classes you want to load as specified above:
 
   package My::Schema::Result::Album;
-  use base qw/DBIx::Class/;
+  use base qw/DBIx::Class::Core/;
 
-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 to force columns to use UTF-8 encoding:
+Load any additional components you may need with the load_components() method,
+and provide component configuration if required. For example, if you want
+automatic row ordering:
 
-  __PACKAGE__->load_components(qw/ ForceUTF8 Core /);
+  __PACKAGE__->load_components(qw/ Ordered /);
+  __PACKAGE__->position_column('rank');
+
+Ordered will refer to a field called 'position' unless otherwise directed.  Here you are defining
+the ordering field to be named 'rank'.  (NOTE: Insert errors may occur if you use the Ordered
+component, but have not defined a position column or have a 'position' field in your row.)
 
 Set the table for your class:
 
@@ -119,7 +125,7 @@ Set the table for your class:
 
 Add columns to your class:
 
-  __PACKAGE__->add_columns(qw/ albumid artist title /);
+  __PACKAGE__->add_columns(qw/ albumid artist title rank /);
 
 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:
@@ -130,28 +136,30 @@ of information that it may be useful to have -- just pass C<add_columns> a hash:
                               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 => '',
+                            },
+                          rank =>
+                            { data_type => 'integer',
+                              size      => 16,
+                              is_nullable => 0,
+                              default_value => 0,
                             }
                          );
 
 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.
+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.
 
 See L<DBIx::Class::ResultSource> for more details of the possible column
 attributes.
@@ -173,34 +181,52 @@ 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::Result::Artist', 'album_id');
+  # in My::Schema::Result::Artist
+  __PACKAGE__->has_many('albums', 'My::Schema::Result::Album', 'artist');
 
 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>
+=head2 Using 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 module (L<DBIx::Class::Schema::Loader>) is an external module, and not part
+of the L<DBIx::Class> distribution. It inspects your database, and automatically
+creates classes for all the tables in your schema.
 
-  package My::Schema;
-  use base qw/DBIx::Class::Schema::Loader/;
+The simplest way to use it is via the L<dbicdump> script from the
+L<DBIx::Class::Schema::Loader> distribution. For example:
+
+    $ dbicdump -o dump_directory=./lib \
+        -o components='["InflateColumn::DateTime"]' \
+        MyApp::Schema dbi:mysql:mydb user pass
+
+If you have a mixed-case database, use the C<preserve_case> option, e.g.:
 
-  __PACKAGE__->loader_options( relationships => 1 );
+    $ dbicdump -o dump_directory=./lib -o preserve_case=1 \
+        -o components='["InflateColumn::DateTime"]' \
+        MyApp::Schema dbi:mysql:mydb user pass
 
-  1;
+If you are using L<Catalyst>, then you can use the helper that comes with
+L<Catalyst::Model::DBIC::Schema>:
 
-The actual autoloading process will occur when you create a connected instance
-of your schema below.
+    $ 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='"'
 
-See the L<DBIx::Class::Schema::Loader> documentation for more information on its
-many options.
+See L<Catalyst::Helper::Model::DBIC::Schema> for more information on this
+helper.
+
+See the L<DBIx::Class::Schema::Loader> and L<DBIx::Class::Schema::Loader::Base>
+documentation for more information on the many loader 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>:
+To connect to your Schema, you need to provide the connection details or a
+database handle.
+
+=head3 Via connection details
+
+The arguments are the same as for L<DBI/connect>:
 
   my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db');
 
@@ -212,7 +238,7 @@ second database you want to access:
 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
+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(
@@ -223,9 +249,19 @@ a special fifth argument to connect:
       { on_connect_do => \@on_connect_sql_statments }
   );
 
-See L<DBIx::Class::Schema::Storage::DBI/connect_info> for more information about
+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
@@ -252,8 +288,8 @@ 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 save your changes to the
+database (by executing the actual C<UPDATE> statement):
 
   $album->update;
 
@@ -374,6 +410,53 @@ 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
+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.) 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_keys (__PACKAGE__->columns);
+
+Note that 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>, 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