X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FManual%2FIntro.pod;h=cd8b0917a461106299c956835a3d2ca3603a165e;hb=b03f30a3a6e04ff27de81710085f9f0aa95b11f0;hp=ce9d3c4474991f218e513f54978ae53ac268a234;hpb=da7372ac69dbef985a717b955e1b00510e17835f;p=dbsrgits%2FDBIx-Class-Historic.git

diff --git a/lib/DBIx/Class/Manual/Intro.pod b/lib/DBIx/Class/Manual/Intro.pod
index ce9d3c4..cd8b091 100644
--- a/lib/DBIx/Class/Manual/Intro.pod
+++ b/lib/DBIx/Class/Manual/Intro.pod
@@ -11,7 +11,7 @@ better way?  You've come to the right place.
 =head1 THE DBIx::Class WAY
 
 Here are a few simple tips that will help you get your bearings with
-DBIx::Class.  
+DBIx::Class.
 
 =head2 Tables become Result classes
 
@@ -29,7 +29,7 @@ besides) The important thing to understand:
 =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!  
+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
@@ -39,18 +39,18 @@ 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.  
+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. 
+You could easily achieve it.
 
-The important thing to understand: 
+The important thing to understand:
 
-  Any time you would reach for a SQL query in DBI, you are 
+  Any time you would reach for a SQL query in DBI, you are
   creating a DBIx::Class::ResultSet.
 
 =head2 Search is like "prepare"
@@ -105,16 +105,18 @@ 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 serial/auto-incrementing primary keys:
+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/ PK::Auto Core /);
+  __PACKAGE__->load_components(qw/ Ordered /);
+  __PACKAGE__->position_column('rank');
 
-C<PK::Auto> is supported for many databases; see L<DBIx::Class::Storage::DBI>
-for more information.
+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:
 
@@ -122,7 +124,7 @@ 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:
@@ -142,19 +144,26 @@ of information that it may be useful to have -- just pass C<add_columns> a hash:
                               is_auto_increment => 0,
                               default_value => '',
                             },
-                          title  => 
+                          title  =>
                             { data_type => 'varchar',
                               size      => 256,
                               is_nullable => 0,
                               is_auto_increment => 0,
                               default_value => '',
+                            },
+                          rank =>
+                            { data_type => 'integer',
+                              size      => 16,
+                              is_nullable => 0,
+                              is_auto_increment => 0,
+                              default_value => '',
                             }
                          );
 
 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::Schema/deploy> for details.
 
 See L<DBIx::Class::ResultSource> for more details of the possible column
 attributes.
@@ -176,7 +185,8 @@ 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.
@@ -202,8 +212,12 @@ 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>:
+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');
 
@@ -215,7 +229,7 @@ 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(
@@ -226,9 +240,19 @@ 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
@@ -255,8 +279,8 @@ 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;
 
@@ -273,7 +297,7 @@ 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({ 
+  my $new_album = $schema->resultset('Album')->create({
     title  => 'Wish You Were Here',
     artist => 'Pink Floyd'
   });
@@ -377,15 +401,58 @@ 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 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 might suffer this
-problem, you will see a warning on startup, with some options as to what
-to do about it. This problem was eliminated in the perl-5.8.8-15.el5_2.1
-package which was issued in September 2008.
+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