=head1 SYNOPSIS
+ ## Creating relationships
MyDB::Schema::Actor->has_many('actorroles' => 'MyDB::Schema::ActorRole',
'actor');
MyDB::Schema::Role->has_many('actorroles' => 'MyDB::Schema::ActorRole',
MyDB::Schema::Role->many_to_many('actors' => 'actorroles', 'actor');
MyDB::Schema::Actor->many_to_many('roles' => 'actorroles', 'role');
- $schema->resultset('Actor')->roles();
- $schema->resultset('Role')->search_related('actors', { Name => 'Fred' });
- $schema->resultset('ActorRole')->add_to_roles({ Name => 'Sherlock Holmes'});
+ ## Using relationships
+ $schema->resultset('Actor')->find({ id => 1})->roles();
+ $schema->resultset('Role')->find({ id => 1 })->actorroles->search_related('actor', { Name => 'Fred' });
+ $schema->resultset('Actor')->add_to_roles({ Name => 'Sherlock Holmes'});
See L<DBIx::Class::Manual::Cookbook> for more.
=head1 DESCRIPTION
+The word I<Relationship> has a specific meaning in DBIx::Class, see
+the definition in the L<Glossary|DBIx::Class::Manual::Glossary/Relationship>.
+
This class provides methods to set up relationships between the tables
in your database model. Relationships are the most useful and powerful
technique that L<DBIx::Class> provides. To create efficient database queries,
=head1 METHODS
-All helper methods take the following arguments:
+All helper methods are called similar to the following template:
+
+ __PACKAGE__->$method_name('relname', 'Foreign::Class', \%cond | \@cond, \%attrs);
- __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>.
+you want to use the default value for it, but still want to set C<\%attrs>.
+
+See L<DBIx::Class::Relationship::Base> for documentation on the
+attributes that are allowed in the C<\%attrs> argument.
-See L<DBIx::Class::Relationship::Base> for a list of valid attributes and valid
-relationship attributes.
=head2 belongs_to
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $our_fk_column|\%cond|\@cond?, \%attrs?
=back
-Creates a relationship where the calling class stores the foreign class's
-primary key in one (or more) of its columns. This relationship defaults to
-using C<$accessor_name> as the foreign key in C<$related_class> to resolve the
-join, unless C<$foreign_key_column> specifies the foreign key column in
-C<$related_class> or C<$cond> specifies a reference to a join condition hash.
+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<$our_fk_column> specifies the foreign key column
+in this class or C<cond> specifies a reference to a join condition hash.
=over
This argument is the name of the method you can call on a
L<DBIx::Class::Row> object to retrieve the instance of the foreign
-class matching this relationship.
+class matching this relationship. This is often called the
+C<relation(ship) name>.
-Use this accessor_name (relation name) in L<DBIx::Class::ResultSet/join>
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
indicated by this relationship.
This is the class name of the table referenced by the foreign key in
this class.
-=item foreign_key_column
+=item our_fk_column
The column name on this class that contains the foreign key.
=item cond
A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+the values are C<self.$our_fk_column>. This is useful for
relations that are across multiple columns.
=back
# in a Book class (where Author has many Books)
- My::DBIC::Schema::Book->belongs_to( author => 'My::DBIC::Schema::Author' );
-
- my $author_obj = $obj->author; # get author object
- $obj->author( $new_author_obj ); # set author object
+ 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');
-The above belongs_to relationship could also have been specified as,
-
- My::DBIC::Schema::Book->belongs_to( author,
- 'My::DBIC::Schema::Author',
- { 'foreign.author' => 'self.author' } );
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
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'});
+ __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 $attr hashref.
+By default, DBIC will return undef and avoid querying the database if a
+C<belongs_to> accessor is called when any part of the foreign key IS NULL. To
+disable this behavior, pass C<< undef_on_null_fk => 0 >> in the C<$attr>
+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> for documentation on relationship
-methods and valid relationship attributes.
+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
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond?, \%attrs?
=back
-Creates a one-to-many relationship, where the corresponding elements of the
-foreign class store the calling class's primary key in one (or more) of its
-columns. This relationship defaults to using C<$accessor_name> as the foreign
-key in C<$related_class> to resolve the join, unless C<$foreign_key_column>
-specifies the foreign key column in C<$related_class> or C<$cond> specifies a
-reference to a join condition hash.
+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<$related_class> or C<cond>
+specifies a reference to a join condition hash.
=over
This argument is the name of the method you can call on a
L<DBIx::Class::Row> object to retrieve a resultset of the related
class restricted to the ones related to the row object. In list
-context it returns the row objects.
+context it returns the row objects. This is often called the
+C<relation(ship) name>.
-Use this accessor_name (relation name) in L<DBIx::Class::ResultSet/join>
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
indicated by this relationship.
This is the class name of the table which contains a foreign key
column containing PK values of this class.
-=item foreign_key_column
+=item their_fk_column
The column name on the related class that contains the foreign key.
=item cond
-A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+A hashref where the keys are C<foreign.$their_fk_column> and
+the values are C<self.$matching_column>. This is useful for
relations that are across multiple columns.
+OR
+
+An arrayref containing an SQL::Abstract-like condition. For example a
+link table where two columns link back to the same table. This is an
+OR condition.
+
+ My::Schema::Item->has_many('rels', 'My::Schema::Relationships',
+ [ { 'foreign.LItemID' => 'self.ID' },
+ { 'foreign.RItemID' => 'self.ID'} ]);
+
=back
# in an Author class (where Author has_many Books)
- My::DBIC::Schema::Author->has_many(books => 'My::DBIC::Schema::Book', 'author');
-
- my $booklist = $obj->books;
- my $booklist = $obj->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/],
});
- my @book_objs = $obj->books;
- my $books_rs = $obj->books;
- ( $books_rs ) = $obj->books_rs;
- $obj->add_to_books(\%col_data);
+ # 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;
-The above C<has_many> relationship could also have been specified with an
-explicit join condition:
+ # create a new book for this author, the relation fields are auto-filled
+ $author->create_related('books', \%col_data);
+ # alternative method for the above
+ $author->add_to_books(\%col_data);
- My::DBIC::Schema::Author->has_many( books => 'My::DBIC::Schema::Book', {
- 'foreign.author' => 'self.author',
- });
Three methods are created when you create a has_many relationship. The first
method is the expected accessor method, C<$accessor_name()>. The second is
almost exactly the same as the accessor method but "_rs" is added to the end of
the method name. This method works just like the normal accessor, except that
-it returns a resultset no matter what, even in list context. The third method,
+it always returns a resultset, even in list context. The third method,
named C<< add_to_$relname >>, will also be added to your Row items; this
allows you to insert new related items, using the same mechanism as in
L<DBIx::Class::Relationship::Base/"create_related">.
If you delete an object in a class with a C<has_many> relationship, all
the related objects will be deleted as well. To turn this behaviour off,
-pass C<< cascade_delete => 0 >> in the C<$attr> hashref. However, any
-database-level cascade or restrict will take precedence over a
-DBIx-Class-based cascading delete.
+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>.
+pass C<< cascade_copy => 0 >> in the C<$attr> hashref. The behaviour
+defaults to C<< cascade_copy => 1 >>.
See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+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
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond?, \%attrs?
=back
Creates an optional one-to-one relationship with a class. This relationship
defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
-resolve the join, unless C<$foreign_key_column> specifies the foreign key
-column in C<$related_class> or C<$cond> specifies a reference to a join
+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 hash.
=over
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.
+class matching this relationship. This is often called the
+C<relation(ship) name>.
-Use this accessor_name (relation name) in L<DBIx::Class::ResultSet/join>
+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.
This is the class name of the table which contains a foreign key
column containing PK values of this class.
-=item foreign_key_column
+=item their_fk_column
The column name on the related class that contains the foreign key.
=item cond
-A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+A hashref where the keys are C<foreign.$their_fk_column> and
+the values are C<self.$matching_column>. This is useful for
relations that are across multiple columns.
=back
- My::DBIC::Schema::Author->might_have( pseudonym =>
- 'My::DBIC::Schema::Pseudonym' );
-
- my $pname = $obj->pseudonym; # to get the Pseudonym object
-
-The above might_have relationship could have been specified as:
-
- My::DBIC::Schema::Author->might_have( pseudonym =>
- 'My::DBIC::Schema::Pseudonym',
- 'author' );
-
-Or even:
-
- My::DBIC::Schema::Author->might_have( pseudonym =>
- 'My::DBIC::Schema::Pseudonym',
- { 'foreign.author' => 'self.author' } );
+ # Author may have an entry in the pseudonym table
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ 'author_id',
+ );
+
+ # OR (same result, assuming the related_class stores our PK)
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ );
+
+ # 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. Any database-level update or delete constraints will override
-this behavior.
+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> for documentation on relationship
-methods and valid relationship attributes.
+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 C<might_have> will warn about this because it's naughty and
+you shouldn't do that.
+
+ "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 want to use C<DBIx::Class::Relationship/belongs_to>.
=head2 has_one
=over 4
-=item Arguments: $accessor_name, $related_class_name, $join_condition?, $attr?
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond?, \%attrs?
=back
- My::DBIC::Schema::Book->has_one(isbn => 'My::DBIC::Schema::ISBN');
+Creates a one-to-one relationship with a class. This relationship
+defaults to using C<$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 hash.
+
+=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
- my $isbn_obj = $obj->isbn; # to get the ISBN object
+=item cond
+
+A hashref where the keys are C<foreign.$their_fk_column> and
+the values are C<self.$matching_column>. This is useful for
+relations that are across multiple columns.
-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> uses a
-left join.
+=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 has exactly one
related row in another table. If the related row might not exist in the foreign
ISBN object.
See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+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
=over 4
-=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, $attr?
+=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, \%attrs?
=back
+C<many_to_many> is a I<Relationship bridge> which has a specific
+meaning in DBIx::Class, see the definition in the
+L<Glossary|DBIx::Class::Manual::Glossary/Relationship bridge>.
+
C<many_to_many> is not strictly a relationship in its own right. Instead, it is
a bridge between two resultsets which provide the same kind of convenience
accessors as true relationships provide. Although the accessor will return a
relation names are then used in the many_to_many call.
In the above example, the Actor class will have 3 many_to_many accessor methods
-set: C<$roles>, C<$add_to_roles>, C<$set_roles>, and similarly named accessors
+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> for documentation on relationship
-methods and valid relationship attributes.
+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
=head1 AUTHORS
-Matt S. Trout <mst@shadowcatsystems.co.uk>
+see L<DBIx::Class>
=head1 LICENSE
projects / dbsrgits/DBIx-Class.git / blobdiff