3 DBIx::Class::Manual::Cookbook - Miscellaneous recipes
11 When you expect a large number of results, you can ask L<DBIx::Class> for a
12 paged resultset, which will fetch only a defined number of records at a time:
14 my $rs = $schema->resultset('Artist')->search(
17 page => 1, # page to return (defaults to 1)
18 rows => 10, # number of results per page
22 return $rs->all(); # all records for page 1
24 The C<page> attribute does not have to be specified in your search:
26 my $rs = $schema->resultset('Artist')->search(
33 return $rs->page(1); # DBIx::Class::ResultSet containing first 10 records
35 In either of the above cases, you can get a L<Data::Page> object for the
36 resultset (suitable for use in e.g. a template) using the C<pager> method:
40 =head3 Complex WHERE clauses
42 Sometimes you need to formulate a query using specific operators:
44 my @albums = $schema->resultset('Album')->search({
45 artist => { 'like', '%Lamb%' },
46 title => { 'like', '%Fear of Fours%' },
49 This results in something like the following C<WHERE> clause:
51 WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
53 Other queries might require slightly more complex logic:
55 my @albums = $schema->resultset('Album')->search({
58 artist => { 'like', '%Smashing Pumpkins%' },
59 title => 'Siamese Dream',
61 artist => 'Starchildren',
65 This results in the following C<WHERE> clause:
67 WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
68 OR artist = 'Starchildren'
70 For more information on generating complex queries, see
71 L<SQL::Abstract/WHERE CLAUSES>.
73 =head3 Arbitrary SQL through a custom ResultSource
75 Sometimes you have to run arbitrary SQL because your query is too complex
76 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
77 be optimized for your database in a special way, but you still want to
78 get the results as a L<DBIx::Class::ResultSet>.
79 The recommended way to accomplish this is by defining a separate ResultSource
80 for your query. You can then inject complete SQL statements using a scalar
81 reference (this is a feature of L<SQL::Abstract>).
83 Say you want to run a complex custom query on your user data, here's what
84 you have to add to your User class:
86 package My::Schema::User;
88 use base qw/DBIx::Class/;
90 # ->load_components, ->table, ->add_columns, etc.
92 # Make a new ResultSource based on the User class
93 my $source = __PACKAGE__->result_source_instance();
94 my $new_source = $source->new( $source );
95 $new_source->source_name( 'UserFriendsComplex' );
97 # Hand in your query as a scalar reference
98 # It will be added as a sub-select after FROM,
99 # so pay attention to the surrounding brackets!
100 $new_source->name( \<<SQL );
101 ( SELECT u.* FROM user u
102 INNER JOIN user_friends f ON u.id = f.user_id
103 WHERE f.friend_user_id = ?
105 SELECT u.* FROM user u
106 INNER JOIN user_friends f ON u.id = f.friend_user_id
107 WHERE f.user_id = ? )
110 # Finally, register your new ResultSource with your Schema
111 My::Schema->register_source( 'UserFriendsComplex' => $new_source );
113 Next, you can execute your complex query using bind parameters like this:
115 my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {},
117 bind => [ 12345, 12345 ]
121 ... and you'll get back a perfect L<DBIx::Class::ResultSet>.
123 =head3 Using specific columns
125 When you only want specific columns from a table, you can use
126 C<columns> to specify which ones you need. This is useful to avoid
127 loading columns with large amounts of data that you aren't about to
130 my $rs = $schema->resultset('Artist')->search(
133 columns => [qw/ name /]
138 # SELECT artist.name FROM artist
140 This is a shortcut for C<select> and C<as>, see below. C<columns>
141 cannot be used together with C<select> and C<as>.
143 =head3 Using database functions or stored procedures
145 The combination of C<select> and C<as> can be used to return the result of a
146 database function or stored procedure as a column value. You use C<select> to
147 specify the source for your column value (e.g. a column name, function, or
148 stored procedure name). You then use C<as> to set the column name you will use
149 to access the returned value:
151 my $rs = $schema->resultset('Artist')->search(
154 select => [ 'name', { LENGTH => 'name' } ],
155 as => [qw/ name name_length /],
160 # SELECT name name, LENGTH( name )
163 Note that the C< as > attribute has absolutely nothing to with the sql
164 syntax C< SELECT foo AS bar > (see the documentation in
165 L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
166 column in your base class (i.e. it was added with C<add_columns>), you
167 just access it as normal. Our C<Artist> class has a C<name> column, so
168 we just use the C<name> accessor:
170 my $artist = $rs->first();
171 my $name = $artist->name();
173 If on the other hand the alias does not correspond to an existing column, you
174 have to fetch the value using the C<get_column> accessor:
176 my $name_length = $artist->get_column('name_length');
178 If you don't like using C<get_column>, you can always create an accessor for
179 any of your aliases using either of these:
181 # Define accessor manually:
182 sub name_length { shift->get_column('name_length'); }
184 # Or use DBIx::Class::AccessorGroup:
185 __PACKAGE__->mk_group_accessors('column' => 'name_length');
187 =head3 SELECT DISTINCT with multiple columns
189 my $rs = $schema->resultset('Foo')->search(
193 { distinct => [ $source->columns ] }
195 as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
199 my $count = $rs->next->get_column('count');
201 =head3 SELECT COUNT(DISTINCT colname)
203 my $rs = $schema->resultset('Foo')->search(
207 { count => { distinct => 'colname' } }
213 =head3 Grouping results
215 L<DBIx::Class> supports C<GROUP BY> as follows:
217 my $rs = $schema->resultset('Artist')->search(
221 select => [ 'name', { count => 'cds.cdid' } ],
222 as => [qw/ name cd_count /],
223 group_by => [qw/ name /]
228 # SELECT name, COUNT( cds.cdid ) FROM artist me
229 # LEFT JOIN cd cds ON ( cds.artist = me.artistid )
232 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
233 are in any way unsure about the use of the attributes above (C< join
234 >, C< select >, C< as > and C< group_by >).
236 =head3 Predefined searches
238 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
239 and define often used searches as methods:
241 package My::DBIC::ResultSet::CD;
244 use base 'DBIx::Class::ResultSet';
246 sub search_cds_ordered {
249 return $self->search(
251 { order_by => 'name DESC' },
257 To use your resultset, first tell DBIx::Class to create an instance of it
258 for you, in your My::DBIC::Schema::CD class:
260 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
262 Then call your new method in your code:
264 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
266 =head2 Using joins and prefetch
268 You can use the C<join> attribute to allow searching on, or sorting your
269 results by, one or more columns in a related table. To return all CDs matching
270 a particular artist name:
272 my $rs = $schema->resultset('CD')->search(
274 'artist.name' => 'Bob Marley'
277 join => [qw/artist/], # join the artist table
282 # SELECT cd.* FROM cd
283 # JOIN artist ON cd.artist = artist.id
284 # WHERE artist.name = 'Bob Marley'
286 If required, you can now sort on any column in the related tables by including
287 it in your C<order_by> attribute:
289 my $rs = $schema->resultset('CD')->search(
291 'artist.name' => 'Bob Marley'
294 join => [qw/ artist /],
295 order_by => [qw/ artist.name /]
300 # SELECT cd.* FROM cd
301 # JOIN artist ON cd.artist = artist.id
302 # WHERE artist.name = 'Bob Marley'
303 # ORDER BY artist.name
305 Note that the C<join> attribute should only be used when you need to search or
306 sort using columns in a related table. Joining related tables when you only
307 need columns from the main table will make performance worse!
309 Now let's say you want to display a list of CDs, each with the name of the
310 artist. The following will work fine:
312 while (my $cd = $rs->next) {
313 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
316 There is a problem however. We have searched both the C<cd> and C<artist> tables
317 in our main query, but we have only returned data from the C<cd> table. To get
318 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
321 SELECT artist.* FROM artist WHERE artist.id = ?
323 A statement like the one above will run for each and every CD returned by our
324 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
327 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
328 This allows you to fetch results from related tables in advance:
330 my $rs = $schema->resultset('CD')->search(
332 'artist.name' => 'Bob Marley'
335 join => [qw/ artist /],
336 order_by => [qw/ artist.name /],
337 prefetch => [qw/ artist /] # return artist data too!
341 # Equivalent SQL (note SELECT from both "cd" and "artist"):
342 # SELECT cd.*, artist.* FROM cd
343 # JOIN artist ON cd.artist = artist.id
344 # WHERE artist.name = 'Bob Marley'
345 # ORDER BY artist.name
347 The code to print the CD list remains the same:
349 while (my $cd = $rs->next) {
350 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
353 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
354 so no additional SQL statements are executed. You now have a much more
357 Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
358 C<has_many> relationships.
360 Also note that C<prefetch> should only be used when you know you will
361 definitely use data from a related table. Pre-fetching related tables when you
362 only need columns from the main table will make performance worse!
364 =head3 Multi-step joins
366 Sometimes you want to join more than one relationship deep. In this example,
367 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
368 contain a specific string:
370 # Relationships defined elsewhere:
371 # Artist->has_many('cds' => 'CD', 'artist');
372 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
374 my $rs = $schema->resultset('Artist')->search(
376 'liner_notes.notes' => { 'like', '%some text%' },
380 'cds' => 'liner_notes'
386 # SELECT artist.* FROM artist
387 # JOIN ( cd ON artist.id = cd.artist )
388 # JOIN ( liner_notes ON cd.id = liner_notes.cd )
389 # WHERE liner_notes.notes LIKE '%some text%'
391 Joins can be nested to an arbitrary level. So if we decide later that we
392 want to reduce the number of Artists returned based on who wrote the liner
395 # Relationship defined elsewhere:
396 # LinerNotes->belongs_to('author' => 'Person');
398 my $rs = $schema->resultset('Artist')->search(
400 'liner_notes.notes' => { 'like', '%some text%' },
401 'author.name' => 'A. Writer'
406 'liner_notes' => 'author'
413 # SELECT artist.* FROM artist
414 # JOIN ( cd ON artist.id = cd.artist )
415 # JOIN ( liner_notes ON cd.id = liner_notes.cd )
416 # JOIN ( author ON author.id = liner_notes.author )
417 # WHERE liner_notes.notes LIKE '%some text%'
418 # AND author.name = 'A. Writer'
420 =head2 Multi-step prefetch
422 From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
423 deep using the same syntax as a multi-step join:
425 my $rs = $schema->resultset('Tag')->search(
435 # SELECT tag.*, cd.*, artist.* FROM tag
436 # JOIN cd ON tag.cd = cd.cdid
437 # JOIN artist ON cd.artist = artist.artistid
439 Now accessing our C<cd> and C<artist> relationships does not need additional
442 my $tag = $rs->first;
443 print $tag->cd->artist->name;
445 =head2 Columns of data
447 If you want to find the sum of a particular column there are several
448 ways, the obvious one is to use search:
450 my $rs = $schema->resultset('Items')->search(
453 select => [ { sum => 'Cost' } ],
454 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
457 my $tc = $rs->first->get_column('total_cost');
459 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
460 returned when you ask the C<ResultSet> for a column using
463 my $cost = $schema->resultset('Items')->get_column('Cost');
466 With this you can also do:
468 my $minvalue = $cost->min;
469 my $maxvalue = $cost->max;
471 Or just iterate through the values of this column only:
473 while ( my $c = $cost->next ) {
477 foreach my $c ($cost->all) {
481 C<ResultSetColumn> only has a limited number of built-in functions, if
482 you need one that it doesn't have, then you can use the C<func> method
485 my $avg = $cost->func('AVERAGE');
487 This will cause the following SQL statement to be run:
489 SELECT AVERAGE(Cost) FROM Items me
491 Which will of course only work if your database supports this function.
492 See L<DBIx::Class::ResultSetColumn> for more documentation.
494 =head2 Using relationships
496 =head3 Create a new row in a related table
498 my $book->create_related('author', { name => 'Fred'});
500 =head3 Search in a related table
502 Only searches for books named 'Titanic' by the author in $author.
504 my $author->search_related('books', { name => 'Titanic' });
506 =head3 Delete data in a related table
508 Deletes only the book named Titanic by the author in $author.
510 my $author->delete_related('books', { name => 'Titanic' });
512 =head3 Ordering a relationship result set
514 If you always want a relation to be ordered, you can specify this when you
515 create the relationship.
517 To order C<< $book->pages >> by descending page_number.
519 Book->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
525 As of version 0.04001, there is improved transaction support in
526 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
527 example of the recommended way to use it:
529 my $genus = $schema->resultset('Genus')->find(12);
537 $genus->add_to_species({ name => 'troglodyte' });
540 $schema->txn_do($coderef2); # Can have a nested transaction
541 return $genus->species;
546 $rs = $schema->txn_do($coderef1);
549 if ($@) { # Transaction failed
550 die "the sky is falling!" #
551 if ($@ =~ /Rollback failed/); # Rollback failed
553 deal_with_failed_transaction();
556 Nested transactions will work as expected. That is, only the outermost
557 transaction will actually issue a commit to the $dbh, and a rollback
558 at any level of any transaction will cause the entire nested
559 transaction to fail. Support for savepoints and for true nested
560 transactions (for databases that support them) will hopefully be added
563 =head2 Many-to-many relationships
565 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
568 # ... set up connection ...
572 __PACKAGE__->table('user');
573 __PACKAGE__->add_columns(qw/id name/);
574 __PACKAGE__->set_primary_key('id');
575 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
576 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
578 package My::UserAddress;
580 __PACKAGE__->table('user_address');
581 __PACKAGE__->add_columns(qw/user address/);
582 __PACKAGE__->set_primary_key(qw/user address/);
583 __PACKAGE__->belongs_to('user' => 'My::User');
584 __PACKAGE__->belongs_to('address' => 'My::Address');
588 __PACKAGE__->table('address');
589 __PACKAGE__->add_columns(qw/id street town area_code country/);
590 __PACKAGE__->set_primary_key('id');
591 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
592 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
594 $rs = $user->addresses(); # get all addresses for a user
595 $rs = $address->users(); # get all users for an address
597 =head2 Setting default values for a row
599 It's as simple as overriding the C<new> method. Note the use of
603 my ( $self, $attrs ) = @_;
605 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
607 my $new = $class->next::method($attrs);
612 For more information about C<next::method>, look in the L<Class::C3>
613 documentation. See also L<DBIx::Class::Manual::Component> for more
614 ways to write your own base classes to do this.
616 People looking for ways to do "triggers" with DBIx::Class are probably
617 just looking for this.
619 =head2 Stringification
621 Employ the standard stringification technique by using the C<overload>
624 To make an object stringify itself as a single column, use something
625 like this (replace C<foo> with the column/method of your choice):
627 use overload '""' => sub { shift->name}, fallback => 1;
629 For more complex stringification, you can use an anonymous subroutine:
631 use overload '""' => sub { $_[0]->name . ", " .
632 $_[0]->address }, fallback => 1;
634 =head3 Stringification Example
636 Suppose we have two tables: C<Product> and C<Category>. The table
639 Product(id, Description, category)
640 Category(id, Description)
642 C<category> is a foreign key into the Category table.
644 If you have a Product object C<$obj> and write something like
648 things will not work as expected.
650 To obtain, for example, the category description, you should add this
651 method to the class defining the Category table:
653 use overload "" => sub {
656 return $self->Description;
659 =head2 Disconnecting cleanly
661 If you find yourself quitting an app with Control-C a lot during
662 development, you might like to put the following signal handler in
663 your main database class to make sure it disconnects cleanly:
666 __PACKAGE__->storage->disconnect;
669 =head2 Schema import/export
671 To create a DBIx::Class schema from an existing database, use
672 L<DBIx::Class::Schema::Loader>'s C<make_schema_at>:
674 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
676 The following functionality requires you to have L<SQL::Translator>
677 (also known as "SQL Fairy") installed.
679 To create a set of database-specific .sql files for the above schema:
681 my $schema = My::Schema->connect($dsn);
682 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
687 By default this will create schema files in the current directory, for
688 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
690 To create a new database using the schema:
692 my $schema = My::Schema->connect($dsn);
693 $schema->deploy({ add_drop_tables => 1});
695 To import created .sql files using the mysql client:
697 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
699 To create C<ALTER TABLE> conversion scripts to update a database to a
700 newer version of your schema at a later point, first set a new
701 $VERSION in your Schema file, then:
703 my $schema = My::Schema->connect($dsn);
704 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
710 This will produce new database-specific .sql files for the new version
711 of the schema, plus scripts to convert from version 0.1 to 0.2. This
712 requires that the files for 0.1 as created above are available in the
713 given directory to diff against.
716 =head2 Easy migration from class-based to schema-based setup
718 You want to start using the schema-based approach to L<DBIx::Class>
719 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
720 of existing classes that you don't want to move by hand. Try this nifty script
726 my $schema = MyDB->schema_instance;
728 my $translator = SQL::Translator->new(
729 debug => $debug || 0,
730 trace => $trace || 0,
731 no_comments => $no_comments || 0,
732 show_warnings => $show_warnings || 0,
733 add_drop_table => $add_drop_table || 0,
734 validate => $validate || 0,
736 'DBIx::Schema' => $schema,
739 'prefix' => 'My::Schema',
743 $translator->parser('SQL::Translator::Parser::DBIx::Class');
744 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
746 my $output = $translator->translate(@args) or die
747 "Error: " . $translator->error;
751 You could use L<Module::Find> to search for all subclasses in the MyDB::*
752 namespace, which is currently left as an exercise for the reader.
754 =head2 Schema versioning
756 The following example shows simplistically how you might use DBIx::Class to
757 deploy versioned schemas to your customers. The basic process is as follows:
763 Create a DBIx::Class schema
775 Modify schema to change functionality
779 Deploy update to customers
783 =head3 Create a DBIx::Class schema
785 This can either be done manually, or generated from an existing database as
786 described under C<Schema import/export>.
788 =head3 Save the schema
790 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L<Schema
793 =head3 Deploy to customers
795 There are several ways you could deploy your schema. These are probably
796 beyond the scope of this recipe, but might include:
802 Require customer to apply manually using their RDBMS.
806 Package along with your app, making database dump/schema update/tests
807 all part of your install.
811 =head3 Modify the schema to change functionality
813 As your application evolves, it may be necessary to modify your schema
814 to change functionality. Once the changes are made to your schema in
815 DBIx::Class, export the modified schema and the conversion scripts as
816 in L<Schema import/export>.
818 =head3 Deploy update to customers
820 Add the L<DBIx::Class::Schema::Versioned> schema component to your
821 Schema class. This will add a new table to your database called
822 C<SchemaVersions> which will keep track of which version is installed
823 and warn if the user trys to run a newer schema version than the
824 database thinks it has.
826 Alternatively, you can send the conversion sql scripts to your
829 =head2 Setting limit dialect for SQL::Abstract::Limit
831 In some cases, SQL::Abstract::Limit cannot determine the dialect of
832 the remote SQL server by looking at the database handle. This is a
833 common problem when using the DBD::JDBC, since the DBD-driver only
834 know that in has a Java-driver available, not which JDBC driver the
835 Java component has loaded. This specifically sets the limit_dialect
836 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
839 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
841 The JDBC bridge is one way of getting access to a MSSQL server from a platform
842 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
844 =head2 Setting quoting for the generated SQL.
846 If the database contains column names with spaces and/or reserved words, they
847 need to be quoted in the SQL queries. This is done using:
849 __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
850 __PACKAGE__->storage->sql_maker->name_sep('.');
852 The first sets the quote characters. Either a pair of matching
853 brackets, or a C<"> or C<'>:
855 __PACKAGE__->storage->sql_maker->quote_char('"');
857 Check the documentation of your database for the correct quote
858 characters to use. C<name_sep> needs to be set to allow the SQL
859 generator to put the quotes the correct place.
861 =head2 Overloading methods
863 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
864 method calls, useful for things like default values and triggers. You have to
865 use calls to C<next::method> to overload methods. More information on using
866 L<Class::C3> with L<DBIx::Class> can be found in
867 L<DBIx::Class::Manual::Component>.
869 =head3 Changing one field whenever another changes
871 For example, say that you have three columns, C<id>, C<number>, and
872 C<squared>. You would like to make changes to C<number> and have
873 C<squared> be automagically set to the value of C<number> squared.
874 You can accomplish this by overriding C<store_column>:
877 my ( $self, $name, $value ) = @_;
878 if ($name eq 'number') {
879 $self->squared($value * $value);
881 $self->next::method($name, $value);
884 Note that the hard work is done by the call to C<next::method>, which
885 redispatches your call to store_column in the superclass(es).
887 =head3 Automatically creating related objects
889 You might have a class C<Artist> which has many C<CD>s. Further, if you
890 want to create a C<CD> object every time you insert an C<Artist> object.
891 You can accomplish this by overriding C<insert> on your objects:
894 my ( $self, @args ) = @_;
895 $self->next::method(@args);
896 $self->cds->new({})->fill_from_artist($self)->insert;
900 where C<fill_from_artist> is a method you specify in C<CD> which sets
901 values in C<CD> based on the data in the C<Artist> object you pass in.
903 =head2 Debugging DBIx::Class objects with Data::Dumper
905 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
906 be hard to find the pertinent data in all the data it can generate.
907 Specifically, if one naively tries to use it like so,
911 my $cd = $schema->resultset('CD')->find(1);
914 several pages worth of data from the CD object's schema and result source will
915 be dumped to the screen. Since usually one is only interested in a few column
916 values of the object, this is not very helpful.
918 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
919 it. Simply define a hook that L<Data::Dumper> will call on the object before
920 dumping it. For example,
927 result_source => undef,
935 local $Data::Dumper::Freezer = '_dumper_hook';
937 my $cd = $schema->resultset('CD')->find(1);
939 # dumps $cd without its ResultSource
941 If the structure of your schema is such that there is a common base class for
942 all your table classes, simply put a method similar to C<_dumper_hook> in the
943 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
944 will automagically clean up your data before printing it. See
945 L<Data::Dumper/EXAMPLES> for more information.
947 =head2 Retrieving a row object's Schema
949 It is possible to get a Schema object from a row object like so:
951 my $schema = $cd->result_source->schema;
952 # use the schema as normal:
953 my $artist_rs = $schema->resultset('Artist');
955 This can be useful when you don't want to pass around a Schema object to every
960 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
961 executed as well as notifications of query completion and transaction
962 begin/commit. If you'd like to profile the SQL you can subclass the
963 L<DBIx::Class::Storage::Statistics> class and write your own profiling
966 package My::Profiler;
969 use base 'DBIx::Class::Storage::Statistics';
971 use Time::HiRes qw(time);
980 $self->print("Executing $sql: ".join(', ', @params)."\n");
989 my $elapsed = sprintf("%0.4f", time() - $start);
990 $self->print("Execution took $elapsed seconds.\n");
996 You can then install that class as the debugging object:
998 __PACKAGE__->storage->debugobj(new My::Profiler());
999 __PACKAGE__->storage->debug(1);
1001 A more complicated example might involve storing each execution of SQL in an
1009 my $elapsed = time() - $start;
1010 push(@{ $calls{$sql} }, {
1016 You could then create average, high and low execution times for an SQL
1017 statement and dig down to see if certain parameters cause aberrant behavior.
1018 You might want to check out L<DBIx::Class::QueryLog> as well.
1020 =head2 Getting the value of the primary key for the last database insert
1022 AKA getting last_insert_id
1024 If you are using PK::Auto, this is straightforward:
1026 my $foo = $rs->create(\%blah);
1028 my $id = $foo->id; # foo->my_primary_key_field will also work.
1030 If you are not using autoincrementing primary keys, this will probably
1031 not work, but then you already know the value of the last primary key anyway.
1033 =head2 Dynamic Sub-classing DBIx::Class proxy classes
1034 (AKA multi-class object inflation from one table)
1036 L<DBIx::Class> classes are proxy classes, therefore some different
1037 techniques need to be employed for more than basic subclassing. In
1038 this example we have a single user table that carries a boolean bit
1039 for admin. We would like like to give the admin users
1040 objects(L<DBIx::Class::Row>) the same methods as a regular user but
1041 also special admin only methods. It doesn't make sense to create two
1042 seperate proxy-class files for this. We would be copying all the user
1043 methods into the Admin class. There is a cleaner way to accomplish
1046 Overriding the C<inflate_result> method within the User proxy-class
1047 gives us the effect we want. This method is called by
1048 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
1049 grab the object being returned, inspect the values we are looking for,
1050 bless it if it's an admin object, and then return it. See the example
1053 B<Schema Definition>
1057 use base qw/DBIx::Class::Schema/;
1059 __PACKAGE__->load_classes(qw/User/);
1062 B<Proxy-Class definitions>
1064 package DB::Schema::User;
1068 use base qw/DBIx::Class/;
1070 ### Defined what our admin class is for ensure_class_loaded
1071 my $admin_class = __PACKAGE__ . '::Admin';
1073 __PACKAGE__->load_components(qw/Core/);
1075 __PACKAGE__->table('users');
1077 __PACKAGE__->add_columns(qw/user_id email password
1078 firstname lastname active
1081 __PACKAGE__->set_primary_key('user_id');
1083 sub inflate_result {
1085 my $ret = $self->next::method(@_);
1086 if( $ret->admin ) {### If this is an admin rebless for extra functions
1087 $self->ensure_class_loaded( $admin_class );
1088 bless $ret, $admin_class;
1094 print "I am a regular user.\n";
1099 package DB::Schema::User::Admin;
1103 use base qw/DB::Schema::User/;
1107 print "I am an admin.\n";
1113 print "I am doing admin stuff\n";
1117 B<Test File> test.pl
1123 my $user_data = { email => 'someguy@place.com',
1124 password => 'pass1',
1127 my $admin_data = { email => 'someadmin@adminplace.com',
1128 password => 'pass2',
1131 my $schema = DB::Schema->connection('dbi:Pg:dbname=test');
1133 $schema->resultset('User')->create( $user_data );
1134 $schema->resultset('User')->create( $admin_data );
1136 ### Now we search for them
1137 my $user = $schema->resultset('User')->single( $user_data );
1138 my $admin = $schema->resultset('User')->single( $admin_data );
1140 print ref $user, "\n";
1141 print ref $admin, "\n";
1143 print $user->password , "\n"; # pass1
1144 print $admin->password , "\n";# pass2; inherited from User
1145 print $user->hello , "\n";# I am a regular user.
1146 print $admin->hello, "\n";# I am an admin.
1148 ### The statement below will NOT print
1149 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
1150 ### The statement below will print
1151 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
1153 =head2 Skip object creation for faster results
1155 DBIx::Class is not built for speed, it's built for convenience and
1156 ease of use, but sometimes you just need to get the data, and skip the
1159 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
1161 my $rs = $schema->resultset('CD');
1163 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1165 my $hash_ref = $rs->find(1);
1169 =head2 Get raw data for blindingly fast results
1171 If the C<inflate_result> solution above is not fast enough for you, you
1172 can use a DBIx::Class to return values exactly as they come out of the
1173 data base with none of the convenience methods wrapped round them.
1175 This is used like so:-
1177 my $cursor = $rs->cursor
1178 while (my @vals = $cursor->next) {
1179 # use $val[0..n] here
1182 You will need to map the array offsets to particular columns (you can
1183 use the I<select> attribute of C<search()> to force ordering).
1185 =head2 Want to know if find_or_create found or created a row?
1187 Just use C<find_or_new> instead, then check C<in_storage>:
1189 my $obj = $rs->find_or_new({ blah => 'blarg' });
1190 unless ($obj->in_storage) {
1192 # do whatever else you wanted if it was a new row
1195 =head3 Wrapping/overloading a column accessor
1197 Problem: Say you have a table "Camera" and want to associate a description
1198 with each camera. For most cameras, you'll be able to generate the description from
1199 the other columns. However, in a few special cases you may want to associate a
1200 custom description with a camera.
1204 In your database schema, define a description field in the "Camera" table that
1205 can contain text and null values.
1207 In DBIC, we'll overload the column accessor to provide a sane default if no
1208 custom description is defined. The accessor will either return or generate the
1209 description, depending on whether the field is null or not.
1211 First, in your "Camera" schema class, define the description field as follows:
1213 __PACKAGE__->add_columns(description => { accessor => '_description' });
1215 Next, we'll define the accessor-wrapper subroutine:
1220 # If there is an update to the column, we'll let the original accessor
1222 return $self->_description(@_) if @_;
1224 # Fetch the column value.
1225 my $description = $self->_description;
1227 # If there's something in the description field, then just return that.
1228 return $description if defined $description && length $descripton;
1230 # Otherwise, generate a description.
1231 return $self->generate_description;