Added note about prefetch and has_many related objects

[dbsrgits/DBIx-Class-Historic.git] / lib / DBIx / Class.pm

package DBIx::Class;

use strict;
use warnings;

use MRO::Compat;

use vars qw($VERSION);
use base qw/Class::C3::Componentised Class::Accessor::Grouped/;
use DBIx::Class::StartupCheck;

sub mk_classdata {
  shift->mk_classaccessor(@_);
}

sub mk_classaccessor {
  my $self = shift;
  $self->mk_group_accessors('inherited', $_[0]);
  $self->set_inherited(@_) if @_ > 1;
}

sub component_base_class { 'DBIx::Class' }

# Always remember to do all digits for the version even if they're 0
# i.e. first release of 0.XX *must* be 0.XX000. This avoids fBSD ports
# brain damage and presumably various other packaging systems too
$VERSION = '0.08114';

$VERSION = eval $VERSION; # numify for warning-free dev releases

sub MODIFY_CODE_ATTRIBUTES {
  my ($class,$code,@attrs) = @_;
  $class->mk_classdata('__attr_cache' => {})
    unless $class->can('__attr_cache');
  $class->__attr_cache->{$code} = [@attrs];
  return ();
}

sub _attr_cache {
  my $self = shift;
  my $cache = $self->can('__attr_cache') ? $self->__attr_cache : {};
  my $rest = eval { $self->next::method };
  return $@ ? $cache : { %$cache, %$rest };
}

1;

=head1 NAME

DBIx::Class - Extensible and flexible object <-> relational mapper.

=head1 GETTING HELP/SUPPORT

The community can be found via:

  Mailing list: http://lists.scsys.co.uk/mailman/listinfo/dbix-class/

  SVN: http://dev.catalyst.perl.org/repos/bast/DBIx-Class/

  SVNWeb: http://dev.catalyst.perl.org/svnweb/bast/browse/DBIx-Class/

  IRC: irc.perl.org#dbix-class

=head1 SYNOPSIS

Create a schema class called MyDB/Schema.pm:

  package MyDB::Schema;
  use base qw/DBIx::Class::Schema/;

  __PACKAGE__->load_namespaces();

  1;

Create a result class to represent artists, who have many CDs, in
MyDB/Schema/Result/Artist.pm:

See L<DBIx::Class::ResultSource> for docs on defining result classes.

  package MyDB::Schema::Result::Artist;
  use base qw/DBIx::Class/;

  __PACKAGE__->load_components(qw/Core/);
  __PACKAGE__->table('artist');
  __PACKAGE__->add_columns(qw/ artistid name /);
  __PACKAGE__->set_primary_key('artistid');
  __PACKAGE__->has_many(cds => 'MyDB::Schema::Result::CD');

  1;

A result class to represent a CD, which belongs to an artist, in
MyDB/Schema/Result/CD.pm:

  package MyDB::Schema::Result::CD;
  use base qw/DBIx::Class/;

  __PACKAGE__->load_components(qw/Core/);
  __PACKAGE__->table('cd');
  __PACKAGE__->add_columns(qw/ cdid artistid title year /);
  __PACKAGE__->set_primary_key('cdid');
  __PACKAGE__->belongs_to(artist => 'MyDB::Schema::Artist', 'artistid');

  1;

Then you can use these classes in your application's code:

  # Connect to your database.
  use MyDB::Schema;
  my $schema = MyDB::Schema->connect($dbi_dsn, $user, $pass, \%dbi_params);

  # Query for all artists and put them in an array,
  # or retrieve them as a result set object.
  # $schema->resultset returns a DBIx::Class::ResultSet
  my @all_artists = $schema->resultset('Artist')->all;
  my $all_artists_rs = $schema->resultset('Artist');

  # Output all artists names
  # $artist here is a DBIx::Class::Row, which has accessors
  # for all its columns. Rows are also subclasses of your Result class.
  foreach $artist (@artists) {
    print $artist->name, "\n";
  }

  # Create a result set to search for artists.
  # This does not query the DB.
  my $johns_rs = $schema->resultset('Artist')->search(
    # Build your WHERE using an SQL::Abstract structure:
    { name => { like => 'John%' } }
  );

  # Execute a joined query to get the cds.
  my @all_john_cds = $johns_rs->search_related('cds')->all;

  # Fetch the next available row.
  my $first_john = $johns_rs->next;

  # Specify ORDER BY on the query.
  my $first_john_cds_by_title_rs = $first_john->cds(
    undef,
    { order_by => 'title' }
  );

  # Create a result set that will fetch the artist data
  # at the same time as it fetches CDs, using only one query.
  my $millennium_cds_rs = $schema->resultset('CD')->search(
    { year => 2000 },
    { prefetch => 'artist' }
  );

  my $cd = $millennium_cds_rs->next; # SELECT ... FROM cds JOIN artists ...
  my $cd_artist_name = $cd->artist->name; # Already has the data so no 2nd query

  # new() makes a DBIx::Class::Row object but doesnt insert it into the DB.
  # create() is the same as new() then insert().
  my $new_cd = $schema->resultset('CD')->new({ title => 'Spoon' });
  $new_cd->artist($cd->artist);
  $new_cd->insert; # Auto-increment primary key filled in after INSERT
  $new_cd->title('Fork');

  $schema->txn_do(sub { $new_cd->update }); # Runs the update in a transaction

  # change the year of all the millennium CDs at once
  $millennium_cds_rs->update({ year => 2002 });

=head1 DESCRIPTION

This is an SQL to OO mapper with an object API inspired by L<Class::DBI>
(with a compatibility layer as a springboard for porting) and a resultset API
that allows abstract encapsulation of database operations. It aims to make
representing queries in your code as perl-ish as possible while still
providing access to as many of the capabilities of the database as possible,
including retrieving related records from multiple tables in a single query,
JOIN, LEFT JOIN, COUNT, DISTINCT, GROUP BY, ORDER BY and HAVING support.

DBIx::Class can handle multi-column primary and foreign keys, complex
queries and database-level paging, and does its best to only query the
database in order to return something you've directly asked for. If a
resultset is used as an iterator it only fetches rows off the statement
handle as requested in order to minimise memory usage. It has auto-increment
support for SQLite, MySQL, PostgreSQL, Oracle, SQL Server and DB2 and is
known to be used in production on at least the first four, and is fork-
and thread-safe out of the box (although your DBD may not be).

This project is still under rapid development, so large new features may be
marked EXPERIMENTAL - such APIs are still usable but may have edge bugs.
Failing test cases are *always* welcome and point releases are put out rapidly
as bugs are found and fixed.

We do our best to maintain full backwards compatibility for published
APIs, since DBIx::Class is used in production in many organisations,
and even backwards incompatible changes to non-published APIs will be fixed
if they're reported and doing so doesn't cost the codebase anything.

The test suite is quite substantial, and several developer releases
are generally made to CPAN before the branch for the next release is
merged back to trunk for a major release.

=head1 WHERE TO GO NEXT

L<DBIx::Class::Manual::DocMap> lists each task you might want help on, and
the modules where you will find documentation.

=head1 AUTHOR

mst: Matt S. Trout <mst@shadowcatsystems.co.uk>

(I mostly consider myself "project founder" these days but the AUTHOR heading
is traditional :)

=head1 CONTRIBUTORS

abraxxa: Alexander Hartmaier <alex_hartmaier@hotmail.com>

aherzog: Adam Herzog <adam@herzogdesigns.com>

andyg: Andy Grundman <andy@hybridized.org>

ank: Andres Kievsky

arcanez: Justin Hunter <justin.d.hunter@gmail.com>

ash: Ash Berlin <ash@cpan.org>

bert: Norbert Csongradi <bert@cpan.org>

blblack: Brandon L. Black <blblack@gmail.com>

bluefeet: Aran Deltac <bluefeet@cpan.org>

bricas: Brian Cassidy <bricas@cpan.org>

brunov: Bruno Vecchi <vecchi.b@gmail.com>

caelum: Rafael Kitover <rkitover@cpan.org>

castaway: Jess Robinson

claco: Christopher H. Laco

clkao: CL Kao

da5id: David Jack Olrik <djo@cpan.org>

debolaz: Anders Nor Berle <berle@cpan.org>

dkubb: Dan Kubb <dan.kubb-cpan@onautopilot.com>

dnm: Justin Wheeler <jwheeler@datademons.com>

dwc: Daniel Westermann-Clark <danieltwc@cpan.org>

dyfrgi: Michael Leuchtenburg <michael@slashhome.org>

frew: Arthur Axel "fREW" Schmidt <frioux@gmail.com>

gphat: Cory G Watson <gphat@cpan.org>

groditi: Guillermo Roditi <groditi@cpan.org>

ilmari: Dagfinn Ilmari MannsE<aring>ker <ilmari@ilmari.org>

jasonmay: Jason May <jason.a.may@gmail.com>

jesper: Jesper Krogh

jgoulah: John Goulah <jgoulah@cpan.org>

jguenther: Justin Guenther <jguenther@cpan.org>

jnapiorkowski: John Napiorkowski <jjn1056@yahoo.com>

jon: Jon Schutz <jjschutz@cpan.org>

jshirley: J. Shirley <jshirley@gmail.com>

konobi: Scott McWhirter

lukes: Luke Saunders <luke.saunders@gmail.com>

marcus: Marcus Ramberg <mramberg@cpan.org>

mattlaw: Matt Lawrence

michaelr: Michael Reddick <michael.reddick@gmail.com>

ned: Neil de Carteret

nigel: Nigel Metheringham <nigelm@cpan.org>

ningu: David Kamholz <dkamholz@cpan.org>

Nniuq: Ron "Quinn" Straight" <quinnfazigu@gmail.org>

norbi: Norbert Buchmuller <norbi@nix.hu>

Numa: Dan Sully <daniel@cpan.org>

oyse: Øystein Torget <oystein.torget@dnv.com>

paulm: Paul Makepeace

penguin: K J Cheetham

perigrin: Chris Prather <chris@prather.org>

peter: Peter Collingbourne <peter@pcc.me.uk>

phaylon: Robert Sedlacek <phaylon@dunkelheit.at>

plu: Johannes Plunien <plu@cpan.org>

quicksilver: Jules Bean

rafl: Florian Ragwitz <rafl@debian.org>

rbuels: Robert Buels <rmb32@cornell.edu>

rdj: Ryan D Johnson <ryan@innerfence.com>

ribasushi: Peter Rabbitson <rabbit+dbic@rabbit.us>

rjbs: Ricardo Signes <rjbs@cpan.org>

robkinyon: Rob Kinyon <rkinyon@cpan.org>

sc_: Just Another Perl Hacker

scotty: Scotty Allen <scotty@scottyallen.com>

semifor: Marc Mims <marc@questright.com>

solomon: Jared Johnson <jaredj@nmgi.com>

spb: Stephen Bennett <stephen@freenode.net>

sszabo: Stephan Szabo <sszabo@bigpanda.com>

teejay : Aaron Trevena <teejay@cpan.org>

Todd Lipcon

Tom Hukins

triode: Pete Gamache <gamache@cpan.org>

typester: Daisuke Murase <typester@cpan.org>

victori: Victor Igumnov <victori@cpan.org>

wdh: Will Hawes

willert: Sebastian Willert <willert@cpan.org>

wreis: Wallace Reis <wreis@cpan.org>

zamolxes: Bogdan Lucaciu <bogdan@wiz.ro>

=head1 COPYRIGHT

Copyright (c) 2005 - 2009 the DBIx::Class L</AUTHOR> and L</CONTRIBUTORS>
as listed above.

=head1 LICENSE

This library is free software and may be distributed under the same terms
as perl itself.

=cut