Base
/);
-=head1 NAME
+=head1 NAME
DBIx::Class::Relationship - Inter-table relationships
=head1 SYNOPSIS
+ ## Creating relationships
+ MyApp::Schema::Actor->has_many('actorroles' => 'MyApp::Schema::ActorRole',
+ 'actor');
+ MyApp::Schema::Role->has_many('actorroles' => 'MyApp::Schema::ActorRole',
+ 'role');
+ MyApp::Schema::ActorRole->belongs_to('role' => 'MyApp::Schema::Role');
+ MyApp::Schema::ActorRole->belongs_to('actor' => 'MyApp::Schema::Actor');
+
+ MyApp::Schema::Role->many_to_many('actors' => 'actorroles', 'actor');
+ MyApp::Schema::Actor->many_to_many('roles' => 'actorroles', 'role');
+
+ ## Using relationships
+ $schema->resultset('Actor')->find({ id => 1})->roles();
+ $schema->resultset('Role')->find({ id => 1 })->actorroles->search_related('actor', { Name => 'Fred' });
+ $schema->resultset('Actor')->add_to_roles({ Name => 'Sherlock Holmes'});
+
+See L<DBIx::Class::Manual::Cookbook> for more.
+
=head1 DESCRIPTION
-This class handles relationships between the tables in your database
-model. It allows you to set up relationships and perform joins on them.
+The word I<Relationship> has a specific meaning in DBIx::Class, see
+the definition in the L<Glossary|DBIx::Class::Manual::Glossary/Relationship>.
+
+This class provides methods to set up relationships between the tables
+in your database model. Relationships are the most useful and powerful
+technique that L<DBIx::Class> provides. To create efficient database queries,
+create relationships between any and all tables that have something in
+common, for example if you have a table Authors:
+
+ ID | Name | Age
+ ------------------
+ 1 | Fred | 30
+ 2 | Joe | 32
+
+and a table Books:
+
+ ID | Author | Name
+ --------------------
+ 1 | 1 | Rulers of the universe
+ 2 | 1 | Rulers of the galaxy
+
+Then without relationships, the method of getting all books by Fred goes like
+this:
+
+ my $fred = $schema->resultset('Author')->find({ Name => 'Fred' });
+ my $fredsbooks = $schema->resultset('Book')->search({ Author => $fred->ID });
+
+With a has_many relationship called "books" on Author (see below for details),
+we can do this instead:
+
+ my $fredsbooks = $schema->resultset('Author')->find({ Name => 'Fred' })->books;
+
+Each relationship sets up an accessor method on the
+L<DBIx::Class::Manual::Glossary/"Row"> objects that represent the items
+of your table. From L<DBIx::Class::Manual::Glossary/"ResultSet"> objects,
+the relationships can be searched using the "search_related" method.
+In list context, each returns a list of Row objects for the related class,
+in scalar context, a new ResultSet representing the joined tables is
+returned. Thus, the calls can be chained to produce complex queries.
+Since the database is not actually queried until you attempt to retrieve
+the data for an actual item, no time is wasted producing them.
+
+ my $cheapfredbooks = $schema->resultset('Author')->find({
+ Name => 'Fred',
+ })->books->search_related('prices', {
+ Price => { '<=' => '5.00' },
+ });
+
+will produce a query something like:
+
+ SELECT * FROM Author me
+ LEFT JOIN Books books ON books.author = me.id
+ LEFT JOIN Prices prices ON prices.book = books.id
+ WHERE prices.Price <= 5.00
+
+all without needing multiple fetches.
Only the helper methods for setting up standard relationship types
-are documented here. For the basic, lower-level methods, see
+are documented here. For the basic, lower-level methods, and a description
+of all the useful *_related methods that you get for free, see
L<DBIx::Class::Relationship::Base>.
=head1 METHODS
-All helper methods take the following arguments:
+All helper methods are called similar to the following template:
+
+ __PACKAGE__->$method_name('relname', 'Foreign::Class', \%cond|\@cond|\&cond?, \%attrs?);
+
+Both C<cond> and C<attrs> are optional. Pass C<undef> for C<cond> if
+you want to use the default value for it, but still want to set C<attrs>.
+
+See L<DBIx::Class::Relationship::Base/condition> for full documentation on
+definition of the C<cond> argument.
+
+See L<DBIx::Class::Relationship::Base/attributes> for documentation on the
+attributes that are allowed in the C<attrs> argument.
- __PACKAGE__>$method_name('relname', 'Foreign::Class', $cond, $attrs);
-
-Both C<$cond> and C<$attrs> are optional. Pass C<undef> for C<$cond> if
-you want to use the default value for it, but still want to set C<$attrs>.
-See L<DBIx::Class::Relationship::Base> for a list of valid attributes.
=head2 belongs_to
- # in a Bar class (where Foo has many Bars)
- __PACKAGE__->belongs_to(foo => Foo);
- my $f_obj = $obj->foo;
- $obj->foo($new_f_obj);
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $our_fk_column|\%cond|\@cond|\$cond?, \%attrs?
+
+=back
+
+Creates a relationship where the calling class stores the foreign
+class's primary key in one (or more) of the calling class columns.
+This relationship defaults to using C<$accessor_name> as the column
+name in this class to resolve the join against the primary key from
+C<$related_class>, unless C<$our_fk_column> specifies the foreign key column
+in this class or C<cond> specifies a reference to a join condition.
+
+=over
+
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve the instance of the foreign
+class matching this relationship. This is often called the
+C<relation(ship) name>.
+
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
+or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
+indicated by this relationship.
+
+=item related_class
+
+This is the class name of the table referenced by the foreign key in
+this class.
+
+=item our_fk_column
+
+The column name on this class that contains the foreign key.
+
+OR
+
+=item cond
+
+A hashref, arrayref or coderef specifying a custom join expression. For
+more info see L<DBIx::Class::Relationship::Base/condition>.
+
+=back
-Creates a relationship where the calling class stores the foreign class's
-primary key in one (or more) of its columns. If $cond is a column name
-instead of a join condition hash, that is used as the name of the column
-holding the foreign key. If $cond is not given, the relname is used as
-the column name.
+ # in a Book class (where Author has many Books)
+ My::DBIC::Schema::Book->belongs_to(
+ author =>
+ 'My::DBIC::Schema::Author',
+ 'author_id'
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Book->belongs_to(
+ author =>
+ 'My::DBIC::Schema::Author',
+ { 'foreign.author_id' => 'self.author_id' }
+ );
+
+ # OR (similar result but uglier accessor name)
+ My::DBIC::Schema::Book->belongs_to(
+ author_id =>
+ 'My::DBIC::Schema::Author'
+ );
+
+ # Usage
+ my $author_obj = $book->author; # get author object
+ $book->author( $new_author_obj ); # set author object
+ $book->author_id(); # get the plain id
+
+ # To retrieve the plain id if you used the ugly version:
+ $book->get_column('author_id');
+
+
+If the relationship is optional -- i.e. the column containing the
+foreign key can be NULL -- then the belongs_to relationship does the
+right thing. Thus, in the example above C<< $obj->author >> would
+return C<undef>. However in this case you would probably want to set
+the L<join_type|DBIx::Class::Relationship/join_type> attribute so that
+a C<LEFT JOIN> is done, which makes complex resultsets involving
+C<join> or C<prefetch> operations work correctly. The modified
+declaration is shown below:
+
+ # in a Book class (where Author has_many Books)
+ __PACKAGE__->belongs_to(
+ author =>
+ 'My::DBIC::Schema::Author',
+ 'author',
+ { join_type => 'left' }
+ );
+
+
+Cascading deletes are off by default on a C<belongs_to>
+relationship. To turn them on, pass C<< cascade_delete => 1 >>
+in the $attr hashref.
+
+By default, DBIC will return undef and avoid querying the database if a
+C<belongs_to> accessor is called when any part of the foreign key IS NULL. To
+disable this behavior, pass C<< undef_on_null_fk => 0 >> in the C<\%attrs>
+hashref.
NOTE: If you are used to L<Class::DBI> relationships, this is the equivalent
of C<has_a>.
+See L<DBIx::Class::Relationship::Base/attributes> for documentation on relationship
+methods and valid relationship attributes. Also see L<DBIx::Class::ResultSet>
+for a L<list of standard resultset attributes|DBIx::Class::ResultSet/ATTRIBUTES>
+which can be assigned to relationships as well.
+
=head2 has_many
- # in a Foo class (where Foo has many Bars)
- __PACKAGE__->has_many(bar => Bar, 'foo');
- my $f_resultset = $obj->foo;
- my $f_resultset = $obj->foo({ name => { LIKE => '%macaroni%' }, { prefetch => [qw/bar/] });
- my @f_obj = $obj->foo;
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond|\&cond?, \%attrs?
+
+=back
+
+Creates a one-to-many relationship where the foreign class refers to
+this class's primary key. This relationship refers to zero or more
+records in the foreign table (e.g. a C<LEFT JOIN>). This relationship
+defaults to using the end of this classes namespace as the foreign key
+in C<$related_class> to resolve the join, unless C<$their_fk_column>
+specifies the foreign key column in C<$related_class> or C<cond>
+specifies a reference to a join condition.
+
+=over
+
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve a resultset of the related
+class restricted to the ones related to the row object. In list
+context it returns the row objects. This is often called the
+C<relation(ship) name>.
+
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
+or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
+indicated by this relationship.
- $obj->add_to_foo(\%col_data);
+=item related_class
-Creates a one-to-many relationship, where the corresponding elements of the
-foreign class store the calling class's primary key in one (or more) of its
-columns. You should pass the name of the column in the foreign class as the
-$cond argument, or specify a complete join condition.
+This is the class name of the table which contains a foreign key
+column containing PK values of this class.
+
+=item their_fk_column
+
+The column name on the related class that contains the foreign key.
+
+OR
+
+=item cond
+
+A hashref, arrayref or coderef specifying a custom join expression. For
+more info see L<DBIx::Class::Relationship::Base/condition>.
+
+=back
+
+ # in an Author class (where Author has_many Books)
+ # assuming related class is storing our PK in "author_id"
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ 'author_id'
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ { 'foreign.author_id' => 'self.id' },
+ );
+
+ # OR (similar result, assuming related_class is storing our PK, in "author")
+ # (the "author" is guessed at from "Author" in the class namespace)
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ );
+
+
+ # Usage
+ # resultset of Books belonging to author
+ my $booklist = $author->books;
+
+ # resultset of Books belonging to author, restricted by author name
+ my $booklist = $author->books({
+ name => { LIKE => '%macaroni%' },
+ { prefetch => [qw/book/],
+ });
+
+ # array of Book objects belonging to author
+ my @book_objs = $author->books;
+
+ # force resultset even in list context
+ my $books_rs = $author->books;
+ ( $books_rs ) = $obj->books_rs;
+
+ # create a new book for this author, the relation fields are auto-filled
+ $author->create_related('books', \%col_data);
+ # alternative method for the above
+ $author->add_to_books(\%col_data);
+
+
+Three methods are created when you create a has_many relationship.
+The first method is the expected accessor method, C<$accessor_name()>.
+The second is almost exactly the same as the accessor method but "_rs"
+is added to the end of the method name, eg C<$accessor_name_rs()>.
+This method works just like the normal accessor, except that it always
+returns a resultset, even in list context. The third method, named C<<
+add_to_$relname >>, will also be added to your Row items; this allows
+you to insert new related items, using the same mechanism as in
+L<DBIx::Class::Relationship::Base/"create_related">.
If you delete an object in a class with a C<has_many> relationship, all
-related objects will be deleted as well. However, any database-level
-cascade or restrict will take precedence.
+the related objects will be deleted as well. To turn this behaviour off,
+pass C<< cascade_delete => 0 >> in the C<$attr> hashref.
+
+The cascaded operations are performed after the requested delete or
+update, so if your database has a constraint on the relationship, it
+will have deleted/updated the related records or raised an exception
+before DBIx::Class gets to perform the cascaded operation.
+
+If you copy an object in a class with a C<has_many> relationship, all
+the related objects will be copied as well. To turn this behaviour off,
+pass C<< cascade_copy => 0 >> in the C<$attr> hashref. The behaviour
+defaults to C<< cascade_copy => 1 >>.
+
+See L<DBIx::Class::Relationship::Base/attributes> for documentation on
+relationship methods and valid relationship attributes. Also see
+L<DBIx::Class::ResultSet> for a L<list of standard resultset
+attributes|DBIx::Class::ResultSet/ATTRIBUTES> which can be assigned to
+relationships as well.
=head2 might_have
- __PACKAGE__->might_have(baz => Baz);
- my $f_obj = $obj->baz; # to get the baz object
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond|\&cond?, \%attrs?
+
+=back
+
+Creates an optional one-to-one relationship with a class. This relationship
+defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
+resolve the join, unless C<$their_fk_column> specifies the foreign key
+column in C<$related_class> or C<cond> specifies a reference to a join
+condition.
+
+=over
+
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve the instance of the foreign
+class matching this relationship. This is often called the
+C<relation(ship) name>.
+
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
+or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
+indicated by this relationship.
+
+=item related_class
+
+This is the class name of the table which contains a foreign key
+column containing PK values of this class.
+
+=item their_fk_column
+
+The column name on the related class that contains the foreign key.
+
+OR
+
+=item cond
+
+A hashref, arrayref or coderef specifying a custom join expression. For
+more info see L<DBIx::Class::Relationship::Base/condition>.
+
+=back
+
+ # Author may have an entry in the pseudonym table
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ 'author_id',
+ );
-Creates an optional one-to-one relationship with a class, where the foreign class
-stores our primary key in one of its columns. Defaults to the primary key of the
-foreign class unless $cond specifies a column or join condition.
+ # OR (same result, assuming the related_class stores our PK)
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ );
-If you update or delete an object in a class with a C<might_have> relationship,
-the related object will be updated or deleted as well. Any database-level update
-or delete constraints will override this behavior.
+ # OR (same result)
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ { 'foreign.author_id' => 'self.id' },
+ );
+
+ # Usage
+ my $pname = $author->pseudonym; # to get the Pseudonym object
+
+If you update or delete an object in a class with a C<might_have>
+relationship, the related object will be updated or deleted as well. To
+turn off this behavior, add C<< cascade_delete => 0 >> to the C<$attr>
+hashref.
+
+The cascaded operations are performed after the requested delete or
+update, so if your database has a constraint on the relationship, it
+will have deleted/updated the related records or raised an exception
+before DBIx::Class gets to perform the cascaded operation.
+
+See L<DBIx::Class::Relationship::Base/attributes> for documentation on
+relationship methods and valid relationship attributes. Also see
+L<DBIx::Class::ResultSet> for a L<list of standard resultset
+attributes|DBIx::Class::ResultSet/ATTRIBUTES> which can be assigned to
+relationships as well.
+
+Note that if you supply a condition on which to join, and the column in the
+current table allows nulls (i.e., has the C<is_nullable> attribute set to a
+true value), than C<might_have> will warn about this because it's naughty and
+you shouldn't do that. The warning will look something like:
+
+ "might_have/has_one" must not be on columns with is_nullable set to true (MySchema::SomeClass/key)
+
+If you must be naughty, you can suppress the warning by setting
+C<DBIC_DONT_VALIDATE_RELS> environment variable to a true value. Otherwise,
+you probably just meant to use C<DBIx::Class::Relationship/belongs_to>.
=head2 has_one
- __PACKAGE__->has_one(gorch => Gorch);
- my $f_obj = $obj->gorch;
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond|\&cond?, \%attrs?
+
+=back
+
+Creates a one-to-one relationship with a class. This relationship
+defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
+resolve the join, unless C<$their_fk_column> specifies the foreign key
+column in C<$related_class> or C<cond> specifies a reference to a join
+condition.
+
+=over
+
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve the instance of the foreign
+class matching this relationship. This is often called the
+C<relation(ship) name>.
+
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
+or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
+indicated by this relationship.
+
+=item related_class
+
+This is the class name of the table which contains a foreign key
+column containing PK values of this class.
+
+=item their_fk_column
+
+The column name on the related class that contains the foreign key.
-Creates a one-to-one relationship with another class. This is just like C<might_have>,
-except the implication is that the other object is always present. The only different
-between C<has_one> and C<might_have> is that C<has_one> uses an (ordinary) inner join,
-whereas C<might_have> uses a left join.
+OR
+=item cond
+
+A hashref, arrayref or coderef specifying a custom join expression. For
+more info see L<DBIx::Class::Relationship::Base/condition>.
+
+=back
+
+ # Every book has exactly one ISBN
+ My::DBIC::Schema::Book->has_one(
+ isbn =>
+ 'My::DBIC::Schema::ISBN',
+ 'book_id',
+ );
+
+ # OR (same result, assuming related_class stores our PK)
+ My::DBIC::Schema::Book->has_one(
+ isbn =>
+ 'My::DBIC::Schema::ISBN',
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Book->has_one(
+ isbn =>
+ 'My::DBIC::Schema::ISBN',
+ { 'foreign.book_id' => 'self.id' },
+ );
+
+ # Usage
+ my $isbn_obj = $book->isbn; # to get the ISBN object
+
+Creates a one-to-one relationship with another class. This is just
+like C<might_have>, except the implication is that the other object is
+always present. The only difference between C<has_one> and
+C<might_have> is that C<has_one> uses an (ordinary) inner join,
+whereas C<might_have> defaults to a left join.
+
+The has_one relationship should be used when a row in the table must
+have exactly one related row in another table. If the related row
+might not exist in the foreign table, use the
+L<DBIx::Class::Relationship/might_have> relationship.
+
+In the above example, each Book in the database is associated with exactly one
+ISBN object.
+
+See L<DBIx::Class::Relationship::Base/attributes> for documentation on
+relationship methods and valid relationship attributes. Also see
+L<DBIx::Class::ResultSet> for a L<list of standard resultset
+attributes|DBIx::Class::ResultSet/ATTRIBUTES> which can be assigned to
+relationships as well.
+
+Note that if you supply a condition on which to join, if the column in the
+current table allows nulls (i.e., has the C<is_nullable> attribute set to a
+true value), than warnings might apply just as with
+L<DBIx::Class::Relationship/might_have>.
=head2 many_to_many
- __PACKAGE__->many_to_many( 'accessorname' => 'a_to_b', 'table_b' );
- my @f_objs = $obj_a->accessorname;
+=over 4
+
+=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, \%attrs?
+
+=back
+
+C<many_to_many> is a I<Relationship bridge> which has a specific
+meaning in DBIx::Class, see the definition in the
+L<Glossary|DBIx::Class::Manual::Glossary/Relationship bridge>.
+
+C<many_to_many> is not strictly a relationship in its own right. Instead, it is
+a bridge between two resultsets which provide the same kind of convenience
+accessors as true relationships provide. Although the accessor will return a
+resultset or collection of objects just like has_many does, you cannot call
+C<related_resultset> and similar methods which operate on true relationships.
+
+=over
+
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve the rows matching this
+relationship.
+
+On a many_to_many, unlike other relationships, this cannot be used in
+L<DBIx::Class::ResultSet/search> to join tables. Use the relations
+bridged across instead.
+
+=item link_rel_name
+
+This is the accessor_name from the has_many relationship we are
+bridging from.
+
+=item foreign_rel_name
+
+This is the accessor_name of the belongs_to relationship in the link
+table that we are bridging across (which gives us the table we are
+bridging to).
+
+=back
+
+To create a many_to_many relationship from Actor to Role:
+
+ My::DBIC::Schema::Actor->has_many( actor_roles =>
+ 'My::DBIC::Schema::ActorRoles',
+ 'actor' );
+ My::DBIC::Schema::ActorRoles->belongs_to( role =>
+ 'My::DBIC::Schema::Role' );
+ My::DBIC::Schema::ActorRoles->belongs_to( actor =>
+ 'My::DBIC::Schema::Actor' );
+
+ My::DBIC::Schema::Actor->many_to_many( roles => 'actor_roles',
+ 'role' );
+
+And, for the reverse relationship, from Role to Actor:
+
+ My::DBIC::Schema::Role->has_many( actor_roles =>
+ 'My::DBIC::Schema::ActorRoles',
+ 'role' );
+
+ My::DBIC::Schema::Role->many_to_many( actors => 'actor_roles', 'actor' );
+
+To add a role for your actor, and fill in the year of the role in the
+actor_roles table:
+
+ $actor->add_to_roles($role, { year => 1995 });
+
+In the above example, ActorRoles is the link table class, and Role is the
+foreign class. The C<$link_rel_name> parameter is the name of the accessor for
+the has_many relationship from this table to the link table, and the
+C<$foreign_rel_name> parameter is the accessor for the belongs_to relationship
+from the link table to the foreign table.
+
+To use many_to_many, existing relationships from the original table to the link
+table, and from the link table to the end table must already exist, these
+relation names are then used in the many_to_many call.
+
+In the above example, the Actor class will have 3 many_to_many accessor methods
+set: C<roles>, C<add_to_roles>, C<set_roles>, and similarly named accessors
+will be created for the Role class for the C<actors> many_to_many
+relationship.
+
+See L<DBIx::Class::Relationship::Base/attributes> for documentation on
+relationship methods and valid relationship attributes. Also see
+L<DBIx::Class::ResultSet> for a L<list of standard resultset
+attributes|DBIx::Class::ResultSet/ATTRIBUTES> which can be assigned to
+relationships as well.
=cut
1;
-=head1 AUTHORS
+=head1 AUTHOR AND CONTRIBUTORS
-Matt S. Trout <mst@shadowcatsystems.co.uk>
+See L<AUTHOR|DBIx::Class/AUTHOR> and L<CONTRIBUTORS|DBIx::Class/CONTRIBUTORS> in DBIx::Class
=head1 LICENSE
projects / dbsrgits/DBIx-Class.git / blobdiff