paged resultset, which will fetch only a small number of records at a time:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
page => 1, # page to return (defaults to 1)
rows => 10, # number of results per page
The C<page> attribute does not have to be specified in your search:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
rows => 10,
}
=head3 Using specific columns
-When you only want selected columns from a table, you can use C<cols> to
-specify which ones you need:
+When you only want specific columns from a table, you can use
+C<columns> to specify which ones you need. This is useful to avoid
+loading columns with large amounts of data that you aren't about to
+use anyway:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
- cols => [qw/ name /]
+ columns => [qw/ name /]
}
);
# Equivalent SQL:
# SELECT artist.name FROM artist
+This is a shortcut for C<select> and C<as>, see below. C<columns>
+cannot be used together with C<select> and C<as>.
+
=head3 Using database functions or stored procedures
The combination of C<select> and C<as> can be used to return the result of a
);
# Equivalent SQL:
- # SELECT name name, LENGTH( name ) name_length
+ # SELECT name name, LENGTH( name )
# FROM artist
-If your alias exists as a column in your base class (i.e. it was added with
-C<add_columns>), you just access it as normal. Our C<Artist> class has a C<name>
-column, so we just use the C<name> accessor:
+Note that the C< as > attribute has absolutely nothing to with the sql
+syntax C< SELECT foo AS bar > (see the documentation in
+L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
+column in your base class (i.e. it was added with C<add_columns>), you
+just access it as normal. Our C<Artist> class has a C<name> column, so
+we just use the C<name> accessor:
my $artist = $rs->first();
my $name = $artist->name();
If on the other hand the alias does not correspond to an existing column, you
-can get the value using the C<get_column> accessor:
+have to fetch the value using the C<get_column> accessor:
my $name_length = $artist->get_column('name_length');
select => [
{ distinct => [ $source->columns ] }
],
- as => [ $source->columns ]
+ as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
}
);
+ my $count = $rs->next->get_column('count');
+
=head3 SELECT COUNT(DISTINCT colname)
my $rs = $schema->resultset('Foo')->search(
# LEFT JOIN cd cds ON ( cds.artist = me.artistid )
# GROUP BY name
+Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
+are in any way unsure about the use of the attributes above (C< join
+>, C< select >, C< as > and C< group_by >).
+
+=head3 Predefined searches
+
+You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
+and define often used searches as methods:
+
+ package My::DBIC::ResultSet::CD;
+ use strict;
+ use warnings;
+ use base 'DBIx::Class::ResultSet';
+
+ sub search_cds_ordered {
+ my ($self) = @_;
+
+ return $self->search(
+ {},
+ { order_by => 'name DESC' },
+ );
+ }
+
+ 1;
+
+To use your resultset, first tell DBIx::Class to create an instance of it
+for you, in your My::DBIC::Schema::CD class:
+
+ __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
+
+Then call your new method in your code:
+
+ my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+
+
+=head3 Predefined searches without writing a ResultSet class
+
+Alternatively you can automatically generate a DBIx::Class::ResultSet
+class by using the ResultSetManager component and tagging your method
+as ResultSet:
+
+ __PACKAGE__->load_components(qw/ ResultSetManager Core /);
+
+ sub search_cds_ordered : ResultSet {
+ my ($self) = @_;
+ return $self->search(
+ {},
+ { order_by => 'name DESC' },
+ );
+ }
+
+Then call your method in the same way from your code:
+
+ my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+
=head2 Using joins and prefetch
You can use the C<join> attribute to allow searching on, or sorting your
queries!
Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
-This allows you to fetch results from a related table as well as the main table
-for your class:
+This allows you to fetch results from related tables in advance:
my $rs = $schema->resultset('CD')->search(
{
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
# WHERE liner_notes.notes LIKE '%some text%'
# AND author.name = 'A. Writer'
+=head2 Multi-step prefetch
+
+From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
+deep using the same syntax as a multi-step join:
+
+ my $rs = $schema->resultset('Tag')->search(
+ {},
+ {
+ prefetch => {
+ cd => 'artist'
+ }
+ }
+ );
+
+ # Equivalent SQL:
+ # SELECT tag.*, cd.*, artist.* FROM tag
+ # JOIN cd ON tag.cd = cd.cdid
+ # JOIN artist ON cd.artist = artist.artistid
+
+Now accessing our C<cd> and C<artist> relationships does not need additional
+SQL statements:
+
+ my $tag = $rs->first;
+ print $tag->cd->artist->name;
+
+=head2 Columns of data
+
+If you want to find the sum of a particular column there are several
+ways, the obvious one is to use search:
+
+ my $rs = $schema->resultset('Items')->search(
+ {},
+ {
+ select => [ { sum => 'Cost' } ],
+ as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
+ }
+ );
+ my $tc = $rs->first->get_column('total_cost');
+
+Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
+returned when you ask the C<ResultSet> for a column using
+C<get_column>:
+
+ my $cost = $schema->resultset('Items')->get_column('Cost');
+ my $tc = $cost->sum;
+
+With this you can also do:
+
+ my $minvalue = $cost->min;
+ my $maxvalue = $cost->max;
+
+Or just iterate through the values of this column only:
+
+ while ( my $c = $cost->next ) {
+ print $c;
+ }
+
+ foreach my $c ($cost->all) {
+ print $c;
+ }
+
+C<ResultSetColumn> only has a limited number of built-in functions, if
+you need one that it doesn't have, then you can use the C<func> method
+instead:
+
+ my $avg = $cost->func('AVERAGE');
+
+This will cause the following SQL statement to be run:
+
+ SELECT AVERAGE(Cost) FROM Items me
+
+Which will of course only work if your database supports this function.
+See L<DBIx::Class::ResultSetColumn> for more documentation.
+
+=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>. Here is an example of the recommended
-way to use it:
+L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
+example of the recommended way to use it:
- my $genus = Genus->find(12);
- eval {
- MyDB->txn_begin;
+ my $genus = $schema->resultset('Genus')->find(12);
+
+ my $coderef2 = sub {
+ $genus->extinct(1);
+ $genus->update;
+ };
+
+ my $coderef1 = sub {
$genus->add_to_species({ name => 'troglodyte' });
$genus->wings(2);
$genus->update;
- cromulate($genus); # Can have a nested transation
- MyDB->txn_commit;
+ $schema->txn_do($coderef2); # Can have a nested transaction
+ return $genus->species;
+ };
+
+ my $rs;
+ eval {
+ $rs = $schema->txn_do($coderef1);
};
- if ($@) {
- # Rollback might fail, too
- eval {
- MyDB->txn_rollback
- };
+
+ if ($@) { # Transaction failed
+ die "the sky is falling!" #
+ if ($@ =~ /Rollback failed/); # Rollback failed
+
+ deal_with_failed_transaction();
}
-Currently, a nested commit will do nothing and a nested rollback will
-die. The code at each level must be sure to call rollback in the case
-of an error, to ensure that the rollback will propagate to the top
-level and be issued. Support for savepoints and for true nested
+Nested transactions will work as expected. That is, only the outermost
+transaction will actually issue a commit to the $dbh, and a rollback
+at any level of any transaction will cause the entire nested
+transaction to fail. Support for savepoints and for true nested
transactions (for databases that support them) will hopefully be added
in the future.
=head2 Many-to-many relationships
-This is straightforward using L<DBIx::Class::Relationship::ManyToMany>:
+This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
package My::DB;
# ... set up connection ...
$attrs->{foo} = 'bar' unless defined $attrs->{foo};
- $class->next::method($attrs);
+ my $new = $class->next::method($attrs);
+
+ return $new;
}
+For more information about C<next::method>, look in the L<Class::C3>
+documentation. See also L<DBIx::Class::Manual::Component> for more
+ways to write your own base classes to do this.
+
+People looking for ways to do "triggers" with DBIx::Class are probably
+just looking for this.
+
=head2 Stringification
Employ the standard stringification technique by using the C<overload>
-module. Replace C<foo> with the column/method of your choice.
+module.
+
+To make an object stringify itself as a single column, use something
+like this (replace C<foo> with the column/method of your choice):
+
+ use overload '""' => sub { shift->name}, fallback => 1;
+
+For more complex stringification, you can use an anonymous subroutine:
+
+ use overload '""' => sub { $_[0]->name . ", " .
+ $_[0]->address }, fallback => 1;
+
+=head3 Stringification Example
+
+Suppose we have two tables: C<Product> and C<Category>. The table
+specifications are:
+
+ Product(id, Description, category)
+ Category(id, Description)
+
+C<category> is a foreign key into the Category table.
+
+If you have a Product object C<$obj> and write something like
+
+ print $obj->category
+
+things will not work as expected.
- use overload '""' => 'foo', fallback => 1;
+To obtain, for example, the category description, you should add this
+method to the class defining the Category table:
+
+ use overload "" => sub {
+ my $self = shift;
+
+ return $self->Description;
+ }, fallback => 1;
=head2 Disconnecting cleanly
your main database class to make sure it disconnects cleanly:
$SIG{INT} = sub {
- __PACKAGE__->storage->dbh->disconnect;
+ __PACKAGE__->storage->disconnect;
};
+=head2 Schema import/export
+
+This functionality requires you to have L<SQL::Translator> (also known as
+"SQL Fairy") installed.
+
+To create a DBIx::Class schema from an existing database:
+
+ sqlt --from DBI
+ --to DBIx::Class::File
+ --prefix "MySchema" > MySchema.pm
+
+To create a MySQL database from an existing L<DBIx::Class> schema, convert the
+schema to MySQL's dialect of SQL:
+
+ sqlt --from SQL::Translator::Parser::DBIx::Class
+ --to MySQL
+ --DBIx::Class "MySchema.pm" > Schema1.sql
+
+And import using the mysql client:
+
+ mysql -h "host" -D "database" -u "user" -p < Schema1.sql
+
+=head2 Easy migration from class-based to schema-based setup
+
+You want to start using the schema-based approach to L<DBIx::Class>
+(see L<SchemaIntro.pod>), but have an established class-based setup with lots
+of existing classes that you don't want to move by hand. Try this nifty script
+instead:
+
+ use MyDB;
+ use SQL::Translator;
+
+ my $schema = MyDB->schema_instance;
+
+ my $translator = SQL::Translator->new(
+ debug => $debug || 0,
+ trace => $trace || 0,
+ no_comments => $no_comments || 0,
+ show_warnings => $show_warnings || 0,
+ add_drop_table => $add_drop_table || 0,
+ validate => $validate || 0,
+ parser_args => {
+ 'DBIx::Schema' => $schema,
+ },
+ producer_args => {
+ 'prefix' => 'My::Schema',
+ },
+ );
+
+ $translator->parser('SQL::Translator::Parser::DBIx::Class');
+ $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
+
+ my $output = $translator->translate(@args) or die
+ "Error: " . $translator->error;
+
+ print $output;
+
+You could use L<Module::Find> to search for all subclasses in the MyDB::*
+namespace, which is currently left as an exercise for the reader.
+
+=head2 Schema versioning
+
+The following example shows simplistically how you might use DBIx::Class to
+deploy versioned schemas to your customers. The basic process is as follows:
+
+=over 4
+
+=item 1.
+
+Create a DBIx::Class schema
+
+=item 2.
+
+Save the schema
+
+=item 3.
+
+Deploy to customers
+
+=item 4.
+
+Modify schema to change functionality
+
+=item 5.
+
+Deploy update to customers
+
+=back
+
+=head3 Create a DBIx::Class schema
+
+This can either be done manually, or generated from an existing database as
+described under C<Schema import/export>.
+
+=head3 Save the schema
+
+Use C<sqlt> to transform your schema into an SQL script suitable for your
+customer's database. E.g. for MySQL:
+
+ sqlt --from SQL::Translator::Parser::DBIx::Class
+ --to MySQL
+ --DBIx::Class "MySchema.pm" > Schema1.mysql.sql
+
+If you need to target databases from multiple vendors, just generate an SQL
+script suitable for each. To support PostgreSQL too:
+
+ sqlt --from SQL::Translator::DBIx::Class
+ --to PostgreSQL
+ --DBIx::Class "MySchema.pm" > Schema1.pgsql.sql
+
+=head3 Deploy to customers
+
+There are several ways you could deploy your schema. These are probably
+beyond the scope of this recipe, but might include:
+
+=over 4
+
+=item 1.
+
+Require customer to apply manually using their RDBMS.
+
+=item 2.
+
+Package along with your app, making database dump/schema update/tests
+all part of your install.
+
+=back
+
+=head3 Modify the schema to change functionality
+
+As your application evolves, it may be necessary to modify your schema to
+change functionality. Once the changes are made to your schema in DBIx::Class,
+export the modified schema as before, taking care not to overwrite the original:
+
+ sqlt --from SQL::Translator::DBIx::Class
+ --to MySQL
+ --DBIx::Class "Anything.pm" > Schema2.mysql.sql
+
+Next, use sqlt-diff to create an SQL script that will update the customer's
+database schema:
+
+ sqlt-diff --to MySQL Schema1=MySQL Schema2=MySQL > SchemaUpdate.mysql.sql
+
+=head3 Deploy update to customers
+
+The schema update can be deployed to customers using the same method as before.
+
+=head2 Setting limit dialect for SQL::Abstract::Limit
+
+In some cases, SQL::Abstract::Limit cannot determine the dialect of
+the remote SQL server by looking at the database handle. This is a
+common problem when using the DBD::JDBC, since the DBD-driver only
+know that in has a Java-driver available, not which JDBC driver the
+Java component has loaded. This specifically sets the limit_dialect
+to Microsoft SQL-server (See more names in SQL::Abstract::Limit
+-documentation.
+
+ __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
+
+The JDBC bridge is one way of getting access to a MSSQL server from a platform
+that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
+
+=head2 Setting quoting for the generated SQL.
+
+If the database contains column names with spaces and/or reserved words, they
+need to be quoted in the SQL queries. This is done using:
+
+ __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
+ __PACKAGE__->storage->sql_maker->name_sep('.');
+
+The first sets the quote characters. Either a pair of matching
+brackets, or a C<"> or C<'>:
+
+ __PACKAGE__->storage->sql_maker->quote_char('"');
+
+Check the documentation of your database for the correct quote
+characters to use. C<name_sep> needs to be set to allow the SQL
+generator to put the quotes the correct place.
+
+=head2 Overloading methods
+
+L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
+method calls. You have to use calls to C<next::method> to overload methods.
+More information on using L<Class::C3> with L<DBIx::Class> can be found in
+L<DBIx::Class::Manual::Component>.
+
+=head3 Changing one field whenever another changes
+
+For example, say that you have three columns, C<id>, C<number>, and
+C<squared>. You would like to make changes to C<number> and have
+C<squared> be automagically set to the value of C<number> squared.
+You can accomplish this by overriding C<store_column>:
+
+ sub store_column {
+ my ( $self, $name, $value ) = @_;
+ if ($name eq 'number') {
+ $self->squared($value * $value);
+ }
+ $self->next::method($name, $value);
+ }
+
+Note that the hard work is done by the call to C<next::method>, which
+redispatches your call to store_column in the superclass(es).
+
+=head3 Automatically creating related objects
+
+You might have a class C<Artist> which has many C<CD>s. Further, if you
+want to create a C<CD> object every time you insert an C<Artist> object.
+You can accomplish this by overriding C<insert> on your objects:
+
+ sub insert {
+ my ( $self, @args ) = @_;
+ $self->next::method(@args);
+ $self->cds->new({})->fill_from_artist($self)->insert;
+ return $self;
+ }
+
+where C<fill_from_artist> is a method you specify in C<CD> which sets
+values in C<CD> based on the data in the C<Artist> object you pass in.
+
+=head2 Debugging DBIx::Class objects with Data::Dumper
+
+L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
+be hard to find the pertinent data in all the data it can generate.
+Specifically, if one naively tries to use it like so,
+
+ use Data::Dumper;
+
+ my $cd = $schema->resultset('CD')->find(1);
+ print Dumper($cd);
+
+several pages worth of data from the CD object's schema and result source will
+be dumped to the screen. Since usually one is only interested in a few column
+values of the object, this is not very helpful.
+
+Luckily, it is possible to modify the data before L<Data::Dumper> outputs
+it. Simply define a hook that L<Data::Dumper> will call on the object before
+dumping it. For example,
+
+ package My::DB::CD;
+
+ sub _dumper_hook {
+ $_[0] = bless {
+ %{ $_[0] },
+ result_source => undef,
+ }, ref($_[0]);
+ }
+
+ [...]
+
+ use Data::Dumper;
+
+ local $Data::Dumper::Freezer = '_dumper_hook';
+
+ my $cd = $schema->resultset('CD')->find(1);
+ print Dumper($cd);
+ # dumps $cd without its ResultSource
+
+If the structure of your schema is such that there is a common base class for
+all your table classes, simply put a method similar to C<_dumper_hook> in the
+base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
+will automagically clean up your data before printing it. See
+L<Data::Dumper/EXAMPLES> for more information.
+
+=head2 Retrieving a row object's Schema
+
+It is possible to get a Schema object from a row object like so:
+
+ my $schema = $cd->result_source->schema;
+ # use the schema as normal:
+ my $artist_rs = $schema->resultset('Artist');
+
+This can be useful when you don't want to pass around a Schema object to every
+method.
+
+=head2 Profiling
+
+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
+mechanism:
+
+ package My::Profiler;
+ use strict;
+
+ use base 'DBIx::Class::Storage::Statistics';
+
+ use Time::HiRes qw(time);
+
+ my $start;
+
+ sub query_start {
+ my $self = shift();
+ my $sql = shift();
+ my $params = @_;
+
+ print "Executing $sql: ".join(', ', @params)."\n";
+ $start = time();
+ }
+
+ sub query_end {
+ my $self = shift();
+ my $sql = shift();
+ my @params = @_;
+
+ printf("Execution took %0.4f seconds.\n", time() - $start);
+ $start = undef;
+ }
+
+ 1;
+
+You can then install that class as the debugging object:
+
+ __PACKAGE__->storage()->debugobj(new My::Profiler());
+ __PACKAGE__->storage()->debug(1);
+
+A more complicated example might involve storing each execution of SQL in an
+array:
+
+ sub query_end {
+ my $self = shift();
+ my $sql = shift();
+ my @params = @_;
+
+ my $elapsed = time() - $start;
+ push(@{ $calls{$sql} }, {
+ params => \@params,
+ elapsed => $elapsed
+ });
+ }
+
+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_result> 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. See the example
+below:
+
+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/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');
+
+=head2 Skip object creation for faster results
+
+DBIx::Class is not built for speed, it's built for convenience and
+ease of use, but sometimes you just need to get the data, and skip the
+fancy objects.
+
+To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
+
+ my $rs = $schema->resultset('CD');
+
+ $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
+
+ my $hash_ref = $rs->find(1);
+
+Wasn't that easy?
+
+=head2 Get raw data for blindingly fast results
+
+If the C<inflate_result> solution above is not fast enough for you, you
+can use a DBIx::Class to return values exactly as they come out of the
+data base with none of the convenience methods wrapped round them.
+
+This is used like so:-
+
+ my $cursor = $rs->cursor
+ while (my @vals = $cursor->next) {
+ # use $val[0..n] here
+ }
+
+You will need to map the array offsets to particular columns (you can
+use the I<select> attribute of C<search()> to force ordering).
+
+=head2 Want to know if find_or_create found or created a row?
+
+Just use C<find_or_new> instead, then check C<in_storage>:
+
+ my $obj = $rs->find_or_new({ blah => 'blarg' });
+ unless ($obj->in_storage) {
+ $obj->insert;
+ # do whatever else you wanted if it was a new row
+ }
+
+=head3 Wrapping/overloading a column accessor
+
+Problem: Say you have a table "Camera" and want to associate a description
+with each camera. For most cameras, you'll be able to generate the description from
+the other columns. However, in a few special cases you may want to associate a
+custom description with a camera.
+
+Solution:
+
+In your database schema, define a description field in the "Camera" table that
+can contain text and null values.
+
+In DBIC, we'll overload the column accessor to provide a sane default if no
+custom description is defined. The accessor will either return or generate the
+description, depending on whether the field is null or not.
+
+First, in your "Camera" schema class, define the description field as follows:
+
+ __PACKAGE__->add_columns(description => { accessor => '_description' });
+
+Next, we'll define the accessor-wrapper subroutine:
+
+ sub description {
+ my $self = shift;
+
+ # If there is an update to the column, we'll let the original accessor
+ # deal with it.
+ return $self->_description(@_) if @_;
+
+ # Fetch the column value.
+ my $description = $self->_description;
+
+ # If there's something in the description field, then just return that.
+ return $description if defined $description && length $descripton;
+
+ # Otherwise, generate a description.
+ return $self->generate_description;
+ }
+
=cut