-=head1 NAME
+=head1 NAME
DBIx::Class::Manual::Cookbook - Miscellaneous recipes
return $rs->all(); # all records for page 1
-The C<page> attribute does not have to be specified in your search:
+ return $rs->page(2); # records for page 2
- my $rs = $schema->resultset('Artist')->search(
- undef,
- {
- rows => 10,
- }
- );
-
- return $rs->page(1); # DBIx::Class::ResultSet containing first 10 records
-
-In either of the above cases, you can get a L<Data::Page> object for the
-resultset (suitable for use in e.g. a template) using the C<pager> method:
+You can get a L<Data::Page> object for the resultset (suitable for use
+in e.g. a template) using the C<pager> method:
return $rs->pager();
This results in something like the following C<WHERE> clause:
- WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
+ WHERE artist LIKE ? AND title LIKE ?
+
+And the following bind values for the placeholders: C<'%Lamb%'>, C<'%Fear of
+Fours%'>.
Other queries might require slightly more complex logic:
=head2 Retrieve one and only one row from a resultset
-Sometimes you need only the first "top" row of a resultset. While this can be
-easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal,
-as a full blown cursor for the resultset will be created and then immediately
-destroyed after fetching the first row object.
-L<< $rs->single|DBIx::Class::ResultSet/single >> is
-designed specifically for this case - it will grab the first returned result
-without even instantiating a cursor.
+Sometimes you need only the first "top" row of a resultset. While this
+can be easily done with L<< $rs->first|DBIx::Class::ResultSet/first
+>>, it is suboptimal, as a full blown cursor for the resultset will be
+created and then immediately destroyed after fetching the first row
+object. L<< $rs->single|DBIx::Class::ResultSet/single >> is designed
+specifically for this case - it will grab the first returned result
+without even instantiating a cursor.
-Before replacing all your calls to C<first()> with C<single()> please observe the
+Before replacing all your calls to C<first()> with C<single()> please observe the
following CAVEATS:
=over
=item *
+
While single() takes a search condition just like search() does, it does
_not_ accept search attributes. However one can always chain a single() to
a search():
- my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single;
+ my $top_cd = $cd_rs->search({}, { order_by => 'rating' })->single;
=item *
+
Since single() is the engine behind find(), it is designed to fetch a
single row per database query. Thus a warning will be issued when the
underlying SELECT returns more than one row. Sometimes however this usage
at the top of the charts at any given time. If you know what you are doing,
you can silence the warning by explicitly limiting the resultset size:
- my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single;
+ my $top_cd = $cd_rs->search ({}, { order_by => 'rating', rows => 1 })->single;
=back
Sometimes you have to run arbitrary SQL because your query is too complex
(e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
-be optimized for your database in a special way, but you still want to
-get the results as a L<DBIx::Class::ResultSet>.
-The recommended way to accomplish this is by defining a separate ResultSource
-for your query. You can then inject complete SQL statements using a scalar
-reference (this is a feature of L<SQL::Abstract>).
-
-Say you want to run a complex custom query on your user data, here's what
-you have to add to your User class:
-
- package My::Schema::User;
-
- use base qw/DBIx::Class/;
-
- # ->load_components, ->table, ->add_columns, etc.
-
- # Make a new ResultSource based on the User class
- my $source = __PACKAGE__->result_source_instance();
- my $new_source = $source->new( $source );
- $new_source->source_name( 'UserFriendsComplex' );
-
- # Hand in your query as a scalar reference
- # It will be added as a sub-select after FROM,
- # so pay attention to the surrounding brackets!
- $new_source->name( \<<SQL );
- ( SELECT u.* FROM user u
- INNER JOIN user_friends f ON u.id = f.user_id
- WHERE f.friend_user_id = ?
- UNION
- SELECT u.* FROM user u
- INNER JOIN user_friends f ON u.id = f.friend_user_id
- WHERE f.user_id = ? )
- SQL
-
- # Finally, register your new ResultSource with your Schema
- My::Schema->register_extra_source( 'UserFriendsComplex' => $new_source );
+be optimized for your database in a special way, but you still want to
+get the results as a L<DBIx::Class::ResultSet>.
+
+This is accomplished by defining a
+L<ResultSource::View|DBIx::Class::ResultSource::View> for your query,
+almost like you would define a regular ResultSource.
+
+ package My::Schema::Result::UserFriendsComplex;
+ use strict;
+ use warnings;
+ use base qw/DBIx::Class::Core/;
+
+ __PACKAGE__->table_class('DBIx::Class::ResultSource::View');
+
+ # ->table, ->add_columns, etc.
+
+ # do not attempt to deploy() this view
+ __PACKAGE__->result_source_instance->is_virtual(1);
+
+ __PACKAGE__->result_source_instance->view_definition(q[
+ SELECT u.* FROM user u
+ INNER JOIN user_friends f ON u.id = f.user_id
+ WHERE f.friend_user_id = ?
+ UNION
+ SELECT u.* FROM user u
+ INNER JOIN user_friends f ON u.id = f.friend_user_id
+ WHERE f.user_id = ?
+ ]);
Next, you can execute your complex query using bind parameters like this:
- my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {},
+ my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {},
{
bind => [ 12345, 12345 ]
}
- ) ];
-
+ );
+
... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
-that you cannot modify the rows it contains, ie. cannot call L</update>,
+that you cannot modify the rows it contains, e.g. cannot call L</update>,
L</delete>, ... on it).
-If you prefer to have the definitions of these custom ResultSources in separate
-files (instead of stuffing all of them into the same resultset class), you can
-achieve the same with subclassing the resultset class and defining the
-ResultSource there:
+Note that you cannot have bind parameters unless is_virtual is set to true.
- package My::Schema::UserFriendsComplex;
+=over
- use My::Schema::User;
- use base qw/My::Schema::User/;
+=item * NOTE
- __PACKAGE__->table('dummy'); # currently must be called before anything else
+If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
+method for custom SQL execution, you are highly encouraged to update your code
+to use a virtual view as above. If you do not want to change your code, and just
+want to suppress the deprecation warning when you call
+L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
+C<deploy> will exclude this "table":
- # Hand in your query as a scalar reference
- # It will be added as a sub-select after FROM,
- # so pay attention to the surrounding brackets!
- __PACKAGE__->name( \<<SQL );
- ( SELECT u.* FROM user u
- INNER JOIN user_friends f ON u.id = f.user_id
- WHERE f.friend_user_id = ?
- UNION
- SELECT u.* FROM user u
- INNER JOIN user_friends f ON u.id = f.friend_user_id
- WHERE f.user_id = ? )
- SQL
+ sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
-TIMTOWDI.
+=back
=head2 Using specific columns
# SELECT name name, LENGTH( name )
# FROM artist
-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:
+Note that the C<as> attribute B<has absolutely nothing to do> with the SQL
+syntax C< SELECT foo AS bar > (see the documentation in
+L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
+generated SQL via the C<-as> field attribute as follows:
+
+ my $rs = $schema->resultset('Artist')->search(
+ {},
+ {
+ join => 'cds',
+ distinct => 1,
+ '+select' => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ],
+ '+as' => [qw/num_cds/],
+ order_by => { -desc => 'amount_of_cds' },
+ }
+ );
+
+ # Equivalent SQL
+ # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds
+ # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
+ # GROUP BY me.artistid, me.name, me.rank, me.charfield
+ # ORDER BY amount_of_cds DESC
+
+
+If your alias exists as a column in your base class (i.e. it was added with
+L<add_columns|DBIx::Class::ResultSource/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();
# Define accessor manually:
sub name_length { shift->get_column('name_length'); }
-
+
# Or use DBIx::Class::AccessorGroup:
__PACKAGE__->mk_group_accessors('column' => 'name_length');
+See also L</Using SQL functions on the left hand side of a comparison>.
+
=head2 SELECT DISTINCT with multiple columns
- my $rs = $schema->resultset('Foo')->search(
+ my $rs = $schema->resultset('Artist')->search(
{},
{
- select => [
- { distinct => [ $source->columns ] }
- ],
- as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
+ columns => [ qw/artist_id name rank/ ],
+ distinct => 1
}
);
+ my $rs = $schema->resultset('Artist')->search(
+ {},
+ {
+ columns => [ qw/artist_id name rank/ ],
+ group_by => [ qw/artist_id name rank/ ],
+ }
+ );
+
+ # Equivalent SQL:
+ # SELECT me.artist_id, me.name, me.rank
+ # FROM artist me
+ # GROUP BY artist_id, name, rank
+
=head2 SELECT COUNT(DISTINCT colname)
- my $rs = $schema->resultset('Foo')->search(
+ my $rs = $schema->resultset('Artist')->search(
{},
{
- select => [
- { count => { distinct => 'colname' } }
- ],
- as => [ 'count' ]
+ columns => [ qw/name/ ],
+ distinct => 1
}
);
- my $count = $rs->next->get_column('count');
+ my $rs = $schema->resultset('Artist')->search(
+ {},
+ {
+ columns => [ qw/name/ ],
+ group_by => [ qw/name/ ],
+ }
+ );
+
+ my $count = $rs->count;
+
+ # Equivalent SQL:
+ # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
=head2 Grouping results
artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
});
-The usual operators ( =, !=, IN, NOT IN, etc) are supported.
+The usual operators ( =, !=, IN, NOT IN, etc.) are supported.
B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
The following will B<not> work:
my $rs = $schema->resultset('CD')->search({
- artist_id => $inside_rs->get_column('id')->as_query,
+ artist_id => $inside_rs->get_column('id')->as_query, # does NOT work
});
=head3 Support
my $rs = $cdrs->search({
year => {
'=' => $cdrs->search(
- { artistid => { '=' => \'me.artistid' } },
+ { artist_id => { '=' => \'me.artist_id' } },
{ alias => 'inner' }
)->get_column('year')->max_rs->as_query,
},
WHERE year = (
SELECT MAX(inner.year)
FROM cd inner
- WHERE artistid = me.artistid
+ WHERE artist_id = me.artist_id
)
-=head3 EXPERIMENTAL
-
-Please note that subqueries are considered an experimental feature.
-
=head2 Predefined searches
You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
-and define often used searches as methods:
+and defining often used searches as methods:
package My::DBIC::ResultSet::CD;
use strict;
1;
-To use your resultset, first tell DBIx::Class to create an instance of it
-for you, in your My::DBIC::Schema::CD class:
+If you're using L<DBIx::Class::Schema/load_namespaces>, simply place the file
+into the C<ResultSet> directory next to your C<Result> directory, and it will
+be automatically loaded.
+
+If however you are still using L<DBIx::Class::Schema/load_classes>, first tell
+DBIx::Class to create an instance of the ResultSet class for you, in your
+My::DBIC::Schema::CD class:
# class definition as normal
- __PACKAGE__->load_components(qw/ Core /);
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('cd');
# tell DBIC to use the custom ResultSet class
=head2 Using SQL functions on the left hand side of a comparison
-Using SQL functions on the left hand side of a comparison is generally
-not a good idea since it requires a scan of the entire table. However,
+Using SQL functions on the left hand side of a comparison is generally not a
+good idea since it requires a scan of the entire table. (Unless your RDBMS
+supports indexes on expressions - including return values of functions - and
+you create an index on the return value of the function in question.) However,
it can be accomplished with C<DBIx::Class> when necessary.
If you do not have quoting on, simply include the function in your search
$rs->search({ 'YEAR(date_of_birth)' => 1979 });
-With quoting on, or for a more portable solution, use the C<where>
-attribute:
+With quoting on, or for a more portable solution, use literal SQL values with
+placeholders:
- $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
+ $rs->search(\[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ]);
-=begin hidden
+ # Equivalent SQL:
+ # SELECT * FROM employee WHERE YEAR(date_of_birth) = ?
-(When the bind args ordering bug is fixed, this technique will be better
-and can replace the one above.)
+ $rs->search({
+ name => 'Bob',
+ -nest => \[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ],
+ });
-With quoting on, or for a more portable solution, use the C<where> and
-C<bind> attributes:
+ # Equivalent SQL:
+ # SELECT * FROM employee WHERE name = ? AND YEAR(date_of_birth) = ?
- $rs->search({}, {
- where => \'YEAR(date_of_birth) = ?',
- bind => [ 1979 ]
- });
+Note: the C<plain_value> string in the C<< [ plain_value => 1979 ] >> part
+should be either the same as the name of the column (do this if the type of the
+return value of the function is the same as the type of the column) or
+otherwise it's essentially a dummy string currently (use C<plain_value> as a
+habit). It is used by L<DBIx::Class> to handle special column types.
-=end hidden
+See also L<SQL::Abstract/Literal SQL with placeholders and bind values
+(subqueries)>.
=head1 JOINS AND PREFETCHING
=head2 Using joins and prefetch
You can use the C<join> attribute to allow searching on, or sorting your
-results by, one or more columns in a related table. To return all CDs matching
-a particular artist name:
+results by, one or more columns in a related table.
+
+This requires that you have defined the L<DBIx::Class::Relationship>. For example :
+
+ My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
+
+To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
my $rs = $schema->resultset('CD')->search(
{
- 'artist.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
- join => 'artist', # join the artist table
+ join => 'artists', # join the artist table
}
);
# JOIN artist ON cd.artist = artist.id
# WHERE artist.name = 'Bob Marley'
+In that example both the join, and the condition use the relationship name rather than the table name
+(see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
+
If required, you can now sort on any column in the related tables by including
-it in your C<order_by> attribute:
+it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
my $rs = $schema->resultset('CD')->search(
{
- 'artist.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
- join => 'artist',
- order_by => [qw/ artist.name /]
+ join => 'artists',
+ order_by => [qw/ artists.name /]
}
);
my $rs = $schema->resultset('CD')->search(
{
- 'artist.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
- join => 'artist',
- order_by => [qw/ artist.name /],
- prefetch => 'artist' # return artist data too!
+ join => 'artists',
+ order_by => [qw/ artists.name /],
+ prefetch => 'artists' # return artist data too!
}
);
so no additional SQL statements are executed. You now have a much more
efficient query.
-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
only need columns from the main table will make performance worse!
=head2 Multi-step prefetch
-From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
+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(
my $schema = $cd->result_source->schema;
# use the schema as normal:
- my $artist_rs = $schema->resultset('Artist');
+ my $artist_rs = $schema->resultset('Artist');
This can be useful when you don't want to pass around a Schema object to every
method.
AKA getting last_insert_id
-If you are using PK::Auto (which is a core component as of 0.07), this is
-straightforward:
+Thanks to the core component PK::Auto, this is straightforward:
my $foo = $rs->create(\%blah);
# do more stuff
=head2 Stringification
-Employ the standard stringification technique by using the C<overload>
+Employ the standard stringification technique by using the L<overload>
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):
+like this (replace C<name> with the column/method of your choice):
use overload '""' => sub { shift->name}, fallback => 1;
# do whatever else you wanted if it was a new row
}
-=head2 Dynamic Sub-classing DBIx::Class proxy classes
+=head2 Static sub-classing DBIx::Class result classes
+
+AKA adding additional relationships/methods/etc. to a model for a
+specific usage of the (shared) model.
+
+B<Schema definition>
+
+ package My::App::Schema;
+
+ use base 'DBIx::Class::Schema';
+
+ # load subclassed classes from My::App::Schema::Result/ResultSet
+ __PACKAGE__->load_namespaces;
+
+ # load classes from shared model
+ load_classes({
+ 'My::Shared::Model::Result' => [qw/
+ Foo
+ Bar
+ /]});
+
+ 1;
+
+B<Result-Subclass definition>
+
+ package My::App::Schema::Result::Baz;
+
+ use strict;
+ use warnings;
+ use base 'My::Shared::Model::Result::Baz';
+
+ # WARNING: Make sure you call table() again in your subclass,
+ # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
+ # and the class name is not correctly registered as a source
+ __PACKAGE__->table('baz');
+
+ sub additional_method {
+ return "I'm an additional method only needed by this app";
+ }
+
+ 1;
+
+=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
+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
+separate 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.
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');
+
+B<Schema Definition>
+
+ package My::Schema;
+
+ use base qw/DBIx::Class::Schema/;
+
+ __PACKAGE__->load_namespaces;
+
+ 1;
+
+
+B<Proxy-Class definitions>
+
+ package My::Schema::Result::User;
+
+ use strict;
+ use warnings;
+ use base qw/DBIx::Class::Core/;
+
+ ### Define what our admin class is, for ensure_class_loaded()
+ my $admin_class = __PACKAGE__ . '::Admin';
+
+ __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 ;
+ }
+
+ 1;
+
+
+ package My::Schema::Result::User::Admin;
+
+ use strict;
+ use warnings;
+ use base qw/My::Schema::Result::User/;
+
+ # This line is important
+ __PACKAGE__->table('users');
+
+ sub hello
+ {
+ print "I am an admin.\n";
+ return;
+ }
+
+ sub do_admin_stuff
+ {
+ print "I am doing admin stuff\n";
+ return ;
+ }
+
+ 1;
+
+B<Test File> test.pl
+
+ use warnings;
+ use strict;
+ use My::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 = My::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');
+
+Alternatively you can use L<DBIx::Class::DynamicSubclass> that implements
+exactly the above functionality.
=head2 Skip row 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?
+Beware, changing the Result class using
+L<DBIx::Class::ResultSet/result_class> will replace any existing class
+completely including any special components loaded using
+load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
+
=head2 Get raw data for blindingly fast results
If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> 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
+exactly as they come out of the database with none of the convenience methods
wrapped round them.
This is used like so:
}
You will need to map the array offsets to particular columns (you can
-use the I<select> attribute of C<search()> to force ordering).
+use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
=head1 RESULTSET OPERATIONS
=head2 Getting Schema from a ResultSet
-To get the schema object from a result set, do the following:
+To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
$rs->result_source->schema
my $rs = $schema->resultset('Items')->search(
{},
- {
+ {
select => [ { sum => 'Cost' } ],
as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
}
print $c;
}
-C<ResultSetColumn> only has a limited number of built-in functions, if
+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:
=head2 Creating a result set from a set of rows
-Sometimes you have a (set of) row objects that you want to put into a
+Sometimes you have a (set of) row objects that you want to put into a
resultset without the need to hit the DB again. You can do that by using the
L<set_cache|DBIx::Class::Resultset/set_cache> method:
=head2 Ordering a relationship result set
-If you always want a relation to be ordered, you can specify this when you
+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, create the relation
as follows:
- __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
+ __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => { -desc => 'page_number'} } );
=head2 Filtering a relationship result set
This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
package My::User;
- use base 'DBIx::Class';
- __PACKAGE__->load_components('Core');
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('user');
__PACKAGE__->add_columns(qw/id name/);
__PACKAGE__->set_primary_key('id');
__PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
package My::UserAddress;
- use base 'DBIx::Class';
- __PACKAGE__->load_components('Core');
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('user_address');
__PACKAGE__->add_columns(qw/user address/);
__PACKAGE__->set_primary_key(qw/user address/);
__PACKAGE__->belongs_to('address' => 'My::Address');
package My::Address;
- use base 'DBIx::Class';
- __PACKAGE__->load_components('Core');
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('address');
__PACKAGE__->add_columns(qw/id street town area_code country/);
__PACKAGE__->set_primary_key('id');
$rs = $user->addresses(); # get all addresses for a user
$rs = $address->users(); # get all users for an address
+ my $address = $user->add_to_addresses( # returns a My::Address instance,
+ # NOT a My::UserAddress instance!
+ {
+ country => 'United Kingdom',
+ area_code => 'XYZ',
+ town => 'London',
+ street => 'Sesame',
+ }
+ );
+
+=head2 Relationships across DB schemas
+
+Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
+is easy as long as the schemas themselves are all accessible via the same DBI
+connection. In most cases, this means that they are on the same database host
+as each other and your connecting database user has the proper permissions to them.
+
+To accomplish this one only needs to specify the DB schema name in the table
+declaration, like so...
+
+ package MyDatabase::Main::Artist;
+ use base qw/DBIx::Class::Core/;
+
+ __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
+
+ __PACKAGE__->add_columns(qw/ artist_id name /);
+ __PACKAGE__->set_primary_key('artist_id');
+ __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
+
+ 1;
+
+Whatever string you specify there will be used to build the "FROM" clause in SQL
+queries.
+
+The big drawback to this is you now have DB schema names hardcoded in your
+class files. This becomes especially troublesome if you have multiple instances
+of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
+the DB schemas are named based on the environment (e.g. database1_dev).
+
+However, one can dynamically "map" to the proper DB schema by overriding the
+L<connection|DBIx::Class::Schama/connection> method in your Schema class and
+building a renaming facility, like so:
+
+ package MyDatabase::Schema;
+ use Moose;
+
+ extends 'DBIx::Class::Schema';
+
+ around connection => sub {
+ my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
+
+ my $postfix = delete $attr->{schema_name_postfix};
+
+ $inner->(@_);
+
+ if ( $postfix ) {
+ $self->append_db_name($postfix);
+ }
+ };
+
+ sub append_db_name {
+ my ( $self, $postfix ) = @_;
+
+ my @sources_with_db
+ = grep
+ { $_->name =~ /^\w+\./mx }
+ map
+ { $self->source($_) }
+ $self->sources;
+
+ foreach my $source (@sources_with_db) {
+ my $name = $source->name;
+ $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
+
+ $source->name($name);
+ }
+ }
+
+ 1;
+
+By overridding the L<connection|DBIx::Class::Schama/connection>
+method and extracting a custom option from the provided \%attr hashref one can
+then simply iterate over all the Schema's ResultSources, renaming them as
+needed.
+
+To use this facility, simply add or modify the \%attr hashref that is passed to
+L<connection|DBIx::Class::Schama/connect>, as follows:
+
+ my $schema
+ = MyDatabase::Schema->connect(
+ $dsn,
+ $user,
+ $pass,
+ {
+ schema_name_postfix => '_dev'
+ # ... Other options as desired ...
+ })
+
+Obviously, one could accomplish even more advanced mapping via a hash map or a
+callback routine.
+
=head1 TRANSACTIONS
As of version 0.04001, there is improved transaction support in
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.
+transaction to fail.
+
+=head2 Nested transactions and auto-savepoints
+
+If savepoints are supported by your RDBMS, it is possible to achieve true
+nested transactions with minimal effort. To enable auto-savepoints via nested
+transactions, supply the C<< auto_savepoint = 1 >> connection attribute.
+
+Here is an example of true nested transactions. In the example, we start a big
+task which will create several rows. Generation of data for each row is a
+fragile operation and might fail. If we fail creating something, depending on
+the type of failure, we want to abort the whole task, or only skip the failed
+row.
+
+ my $schema = MySchema->connect("dbi:Pg:dbname=my_db");
+
+ # Start a transaction. Every database change from here on will only be
+ # committed into the database if the eval block succeeds.
+ eval {
+ $schema->txn_do(sub {
+ # SQL: BEGIN WORK;
+
+ my $job = $schema->resultset('Job')->create({ name=> 'big job' });
+ # SQL: INSERT INTO job ( name) VALUES ( 'big job' );
+
+ for (1..10) {
+
+ # Start a nested transaction, which in fact sets a savepoint.
+ eval {
+ $schema->txn_do(sub {
+ # SQL: SAVEPOINT savepoint_0;
+
+ my $thing = $schema->resultset('Thing')->create({ job=>$job->id });
+ # SQL: INSERT INTO thing ( job) VALUES ( 1 );
+
+ if (rand > 0.8) {
+ # This will generate an error, thus setting $@
+
+ $thing->update({force_fail=>'foo'});
+ # SQL: UPDATE thing SET force_fail = 'foo'
+ # WHERE ( id = 42 );
+ }
+ });
+ };
+ if ($@) {
+ # SQL: ROLLBACK TO SAVEPOINT savepoint_0;
+
+ # There was an error while creating a $thing. Depending on the error
+ # we want to abort the whole transaction, or only rollback the
+ # changes related to the creation of this $thing
+
+ # Abort the whole job
+ if ($@ =~ /horrible_problem/) {
+ print "something horrible happend, aborting job!";
+ die $@; # rethrow error
+ }
+
+ # Ignore this $thing, report the error, and continue with the
+ # next $thing
+ print "Cannot create thing: $@";
+ }
+ # There was no error, so save all changes since the last
+ # savepoint.
+
+ # SQL: RELEASE SAVEPOINT savepoint_0;
+ }
+ });
+ };
+ if ($@) {
+ # There was an error while handling the $job. Rollback all changes
+ # since the transaction started, including the already committed
+ # ('released') savepoints. There will be neither a new $job nor any
+ # $thing entry in the database.
+
+ # SQL: ROLLBACK;
+
+ print "ERROR: $@\n";
+ }
+ else {
+ # There was no error while handling the $job. Commit all changes.
+ # Only now other connections can see the newly created $job and
+ # @things.
+
+ # SQL: COMMIT;
-=head1 SQL
+ print "Ok\n";
+ }
+
+In this example it might be hard to see where the rollbacks, releases and
+commits are happening, but it works just the same as for plain L<<txn_do>>: If
+the C<eval>-block around C<txn_do> fails, a rollback is issued. If the C<eval>
+succeeds, the transaction is committed (or the savepoint released).
+
+While you can get more fine-grained controll using C<svp_begin>, C<svp_release>
+and C<svp_rollback>, it is strongly recommended to use C<txn_do> with coderefs.
+
+=head1 SQL
=head2 Creating Schemas From An Existing Database
-L<DBIx::Class::Schema::Loader> will connect to a database and create a
+L<DBIx::Class::Schema::Loader> will connect to a database and create a
L<DBIx::Class::Schema> and associated sources by examining the database.
-The recommend way of achieving this is to use the
+The recommend way of achieving this is to use the
L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
To create a new database using the schema:
my $schema = My::Schema->connect($dsn);
- $schema->deploy({ add_drop_tables => 1});
+ $schema->deploy({ add_drop_table => 1});
To import created .sql files using the mysql client:
your database.
Make a table class as you would for any other table
-
+
package MyAppDB::Dual;
use strict;
use warnings;
- use base 'DBIx::Class';
- __PACKAGE__->load_components("Core");
+ use base 'DBIx::Class::Core';
__PACKAGE__->table("Dual");
__PACKAGE__->add_columns(
"dummy",
{ data_type => "VARCHAR2", is_nullable => 0, size => 1 },
);
-
+
Once you've loaded your table class select from it using C<select>
and C<as> instead of C<columns>
-
+
my $rs = $schema->resultset('Dual')->search(undef,
{ select => [ 'sydate' ],
as => [ 'now' ]
},
);
-
+
All you have to do now is be careful how you access your resultset, the below
will not work because there is no column called 'now' in the Dual table class
-
+
while (my $dual = $rs->next) {
print $dual->now."\n";
}
# Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
-
+
You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
your Dual class for whatever you wanted to select from dual, but that's just
silly, instead use C<get_column>
-
+
while (my $dual = $rs->next) {
print $dual->get_column('now')."\n";
}
-
+
Or use C<cursor>
-
+
my $cursor = $rs->cursor;
while (my @vals = $cursor->next) {
print $vals[0]."\n";
}
-
+
+In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
+L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
+current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
+"sequence.nextval" anymore from dual. To avoid this problem, just tell
+L<SQL::Translator> to not create table dual:
+
+ my $sqlt_args = {
+ add_drop_table => 1,
+ parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
+ };
+ $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
+
Or use L<DBIx::Class::ResultClass::HashRefInflator>
-
+
$rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
while ( my $dual = $rs->next ) {
print $dual->{now}."\n";
}
-
+
Here are some example C<select> conditions to illustrate the different syntax
-you could use for doing stuff like
+you could use for doing stuff like
C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
-
+
# get a sequence value
select => [ 'A_SEQ.nextval' ],
-
+
# get create table sql
select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
-
+
# get a random num between 0 and 100
select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
-
+
# what year is it?
select => [ { 'extract' => [ \'year from sysdate' ] } ],
-
+
# do some math
select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
-
+
# which day of the week were you born on?
select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
-
+
# select 16 rows from dual
select => [ "'hello'" ],
as => [ 'world' ],
group_by => [ 'cube( 1, 2, 3, 4 )' ],
-
-
+
+
=head2 Adding Indexes And Functions To Your SQL
Often you will want indexes on columns on your table to speed up searching. To
-do this, create a method called C<sqlt_deploy_hook> in the relevant source
-class (refer to the advanced
+do this, create a method called C<sqlt_deploy_hook> in the relevant source
+class (refer to the advanced
L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
to share a hook between multiple sources):
- package My::Schema::Artist;
+ package My::Schema::Result::Artist;
__PACKAGE__->table('artist');
__PACKAGE__->add_columns(id => { ... }, name => { ... })
1;
-Sometimes you might want to change the index depending on the type of the
+Sometimes you might want to change the index depending on the type of the
database for which SQL is being generated:
my ($db_type = $sqlt_table->schema->translator->producer_type)
=~ s/^SQL::Translator::Producer:://;
-You can also add hooks to the schema level to stop certain tables being
+You can also add hooks to the schema level to stop certain tables being
created:
package My::Schema;
Add the L<DBIx::Class::Schema::Versioned> schema component to your
Schema class. This will add a new table to your database called
C<dbix_class_schema_vesion> which will keep track of which version is installed
-and warn if the user trys to run a newer schema version than the
+and warn if the user tries to run a newer schema version than the
database thinks it has.
-Alternatively, you can send the conversion sql scripts to your
+Alternatively, you can send the conversion SQL scripts to your
customers as above.
-=head2 Setting quoting for the generated SQL.
+=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('.');
+ $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
+ $schema->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('"');
+
+ $schema->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.
-In most cases you should set these as part of the arguments passed to
+In most cases you should set these as part of the arguments passed to
L<DBIx::Class::Schema/connect>:
my $schema = My::Schema->connect(
}
)
+In some cases, quoting will be required for all users of a schema. To enforce
+this, you can also overload the C<connection> method for your schema class:
+
+ sub connection {
+ my $self = shift;
+ my $rv = $self->next::method( @_ );
+ $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
+ $rv->storage->sql_maker->name_sep('.');
+ return $rv;
+ }
+
=head2 Setting limit dialect for SQL::Abstract::Limit
In some cases, SQL::Abstract::Limit cannot determine the dialect of
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)
-The limit dialect can also be set at connect time by specifying a
+The limit dialect can also be set at connect time by specifying a
C<limit_dialect> key in the final hash as shown above.
=head2 Working with PostgreSQL array types
}
);
-In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
+In conditions (e.g. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
methods) you cannot directly use array references (since this is interpreted as
a list of values to be C<OR>ed), but you can use the following syntax to force
passing them as bind values:
arrayrefs together with the column name, like this: C<< [column_name => value]
>>.
-=head1 BOOTSTRAPPING/MIGRATING
+=head1 BOOTSTRAPPING/MIGRATING
=head2 Easy migration from class-based to schema-based setup
use MyDB;
use SQL::Translator;
-
+
my $schema = MyDB->schema_instance;
-
- my $translator = SQL::Translator->new(
+
+ my $translator = SQL::Translator->new(
debug => $debug || 0,
trace => $trace || 0,
no_comments => $no_comments || 0,
'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::*
return $new;
}
-For more information about C<next::method>, look in the L<Class::C3>
+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.
+just looking for this.
=head2 Changing one field whenever another changes
-For example, say that you have three columns, C<id>, C<number>, and
+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>:
=head2 Automatically creating related objects
-You might have a class C<Artist> which has many C<CD>s. Further, if you
+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> on your objects:
Typically L<DBIx::Class> result classes start off with
- use base qw/DBIx::Class/;
- __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
+ use base qw/DBIx::Class::Core/;
+ __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
If this preamble is moved into a common base class:-
package MyDBICbase;
-
- use base qw/DBIx::Class/;
- __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
+
+ use base qw/DBIx::Class::Core/;
+ __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
1;
and each result class then uses this as a base:-
to load the result classes. This will use L<Module::Find|Module::Find>
to find and load the appropriate modules. Explicitly defining the
classes you wish to load will remove the overhead of
-L<Module::Find|Module::Find> and the related directory operations:-
+L<Module::Find|Module::Find> and the related directory operations:
__PACKAGE__->load_classes(qw/ CD Artist Track /);
syntax to load the appropriate classes there is not a direct alternative
avoiding L<Module::Find|Module::Find>.
+=head1 MEMORY USAGE
+
+=head2 Cached statements
+
+L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
+This is normally a good idea, but if too many statements are cached, the database may use too much
+memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
+to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
+
+ # print all currently cached prepared statements
+ print for keys %{$schema->storage->dbh->{CachedKids}};
+ # get a count of currently cached prepared statements
+ my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
+
+If it's appropriate, you can simply clear these statements, automatically deallocating them in the
+database:
+
+ my $kids = $schema->storage->dbh->{CachedKids};
+ delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
+
+But what you probably want is to expire unused statements and not those that are used frequently.
+You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
+
+ use Tie::Cache;
+ use DB::Main;
+ my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
+ on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },
+ });
+
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff