__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:
__PACKAGE__->table('album');
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(
{ 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
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. While in a RDBMS you can safely change any column within a
-row, you can not do the same in DBIC because B<you will be breaking the tie
-between a specific L<DBIx::Class::Row> object and a specific row in your
-database>. Any time you call a CRUD operation on a row (e.g.
+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 B<current values> of the
+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:
+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
L<update|DBIx::Class::ResultSet/update>,
L<delete|DBIx::Class::ResultSet/delete>
-For example, the following would not work:
+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;
+ ->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
+ $schema->resultset('People')
+ ->search({ last_name => 'Dantes' })
+ ->update({ children => 2 }); # <-- update's ALL Dantes to have children of 2
=head2 Problems on RHEL5/CentOS5