so no additional SQL statements are executed. You now have a much more
efficient query.
-Note that as of L<DBIx::Class> 0.04, C<prefetch> cannot be used with
-C<has_many> relationships. You will get an error along the lines of "No
-accessor for prefetched ..." if you try.
+Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
+C<has_many> relationships.
Also note that C<prefetch> should only be used when you know you will
definitely use data from a related table. Pre-fetching related tables when you
my $tag = $rs->first;
print $tag->cd->artist->name;
+=head2 Using relationships
+
+=head3 Create a new row in a related table
+
+ my $book->create_related('author', { name => 'Fred'});
+
+=head3 Search in a related table
+
+Only searches for books named 'Titanic' by the author in $author.
+
+ my $author->search_related('books', { name => 'Titanic' });
+
+=head3 Delete data in a related table
+
+Deletes only the book named Titanic by the author in $author.
+
+ my $author->delete_related('books', { name => 'Titanic' });
+
+=head3 Ordering a relationship result set
+
+If you always want a relation to be ordered, you can specify this when you
+create the relationship.
+
+To order C<< $book->pages >> by descending page_number.
+
+ Book->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
+
+
+
=head2 Transactions
As of version 0.04001, there is improved transaction support in
-L<DBIx::Class::Storage::DBI> and L<DBIx::Class::Schema>. Here is an
+L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
example of the recommended way to use it:
my $genus = $schema->resultset('Genus')->find(12);
+ my $coderef2 = sub {
+ $genus->extinct(1);
+ $genus->update;
+ };
+
my $coderef1 = sub {
- my ($schema, $genus, $code) = @_;
$genus->add_to_species({ name => 'troglodyte' });
$genus->wings(2);
$genus->update;
- $schema->txn_do($code, $genus); # Can have a nested transaction
+ $schema->txn_do($coderef2); # Can have a nested transaction
return $genus->species;
};
- my $coderef2 = sub {
- my ($genus) = @_;
- $genus->extinct(1);
- $genus->update;
- };
-
my $rs;
eval {
- $rs = $schema->txn_do($coderef1, $schema, $genus, $coderef2);
+ $rs = $schema->txn_do($coderef1);
};
if ($@) { # Transaction failed
You might have a class C<Artist> which has many C<CD>s. Further, you
want to create a C<CD> object every time you insert an C<Artist> object.
-You can accomplish this by overriding C<insert>:
+You can accomplish this by overriding C<insert> on your objects:
sub insert {
- my ( $class, $args_ref ) = @_;
- my $self = $class->next::method($args_ref);
+ my ( $self, @args ) = @_;
+ $self->next::method(@args);
$self->cds->new({})->fill_from_artist($self)->insert;
return $self;
}
use Data::Dumper;
- $Data::Dumper::Freezer = '_dumper_hook';
+ local $Data::Dumper::Freezer = '_dumper_hook';
my $cd = $schema->resultset('CD')->find(1);
print Dumper($cd);
=head2 Profiling
-When you enable L<DBIx::Class::Storage::DBI>'s debugging it prints the SQL
+When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
executed as well as notifications of query completion and transaction
begin/commit. If you'd like to profile the SQL you can subclass the
L<DBIx::Class::Storage::Statistics> class and write your own profiling
You could then create average, high and low execution times for an SQL
statement and dig down to see if certain parameters cause aberrant behavior.
+=head2 Getting the value of the primary key for the last database insert
+
+AKA getting last_insert_id
+
+If you are using PK::Auto, this is straightforward:
+
+ my $foo = $rs->create(\%blah);
+ # do more stuff
+ my $id = $foo->id; # foo->my_primary_key_field will also work.
+
+If you are not using autoincrementing primary keys, this will probably
+not work, but then you already know the value of the last primary key anyway.
+
+=head2 Dynamic Sub-classing DBIx::Class proxy classes
+(AKA multi-class object inflation from one table)
+
+L<DBIx::Class> classes are proxy classes, therefore some different techniques
+need to be employed for more than basic subclassing. In this example we have
+a single user table that carries a boolean bit for admin. We would like
+like to give the admin users objects(L<DBIx::Class::Row>) the same methods as
+a regular user but also special admin only methods. It doesn't make sense to
+create two seperate proxy-class files for this. We would be copying all the
+user methods into the Admin class. There is a cleaner way to accomplish this.
+
+Overriding the C<inflate_results()> method within the User proxy-class gives
+us the effect we want. This method is called by L<DBIx::Class::ResultSet> when
+inflating a result from storage. So we grab the object being returned, inspect
+the values we are looking for, bless it if it's an admin object, and then
+return it. Running the test file below will confirm this works.
+
+B<Schema Definition>
+
+ package DB::Schema;
+
+ use base qw/DBIx::Class::Schema/;
+
+ __PACKAGE__->load_classes(qw/User/);
+
+
+B<Proxy-Class definitions>
+
+ package DB::Schema::User;
+
+ use strict;
+ use warnings;
+ use base qw/DBIx::Class/;
+
+ ### Defined what our admin class is for ensure_class_loaded
+ my $admin_class = __PACKAGE__ . '::Admin';
+
+ __PACKAGE__->load_components(qw/PK::Auto Core/);
+
+ __PACKAGE__->table('users');
+
+ __PACKAGE__->add_columns(qw/user_id email password
+ firstname lastname active
+ admin/);
+
+ __PACKAGE__->set_primary_key('user_id');
+
+ sub inflate_result {
+ my $self = shift;
+ my $ret = $self->next::method(@_);
+ if( $ret->admin ) {### If this is an admin rebless for extra functions
+ $self->ensure_class_loaded( $admin_class );
+ bless $ret, $admin_class;
+ }
+ return $ret;
+ }
+
+ sub hello {
+ print "I am a regular user.\n";
+ return ;
+ }
+
+
+ package DB::Schema::User::Admin;
+
+ use strict;
+ use warnings;
+ use base qw/DB::Schema::User/;
+
+ sub hello
+ {
+ print "I am an admin.\n";
+ return;
+ }
+
+ sub do_admin_stuff
+ {
+ print "I am doing admin stuff\n";
+ return ;
+ }
+
+B<Test File> test.pl
+
+ use warnings;
+ use strict;
+ use DB::Schema;
+
+ my $user_data = { email => 'someguy@place.com',
+ password => 'pass1',
+ admin => 0 };
+
+ my $admin_data = { email => 'someadmin@adminplace.com',
+ password => 'pass2',
+ admin => 1 };
+
+ my $schema = DB::Schema->connection('dbi:Pg:dbname=test');
+
+ $schema->resultset('User')->create( $user_data );
+ $schema->resultset('User')->create( $admin_data );
+
+ ### Now we search for them
+ my $user = $schema->resultset('User')->single( $user_data );
+ my $admin = $schema->resultset('User')->single( $admin_data );
+
+ print ref $user, "\n";
+ print ref $admin, "\n";
+
+ print $user->password , "\n"; # pass1
+ print $admin->password , "\n";# pass2; inherited from User
+ print $user->hello , "\n";# I am a regular user.
+ print $admin->hello, "\n";# I am an admin.
+
+ ### The statement below will NOT print
+ print "I can do admin stuff\n" if $user->can('do_admin_stuff');
+ ### The statement below will print
+ print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
+
=cut