3 DBIx::Class::Manual::Cookbook - Miscellaneous recipes
9 When you expect a large number of results, you can ask L<DBIx::Class> for a
10 paged resultset, which will fetch only a defined number of records at a time:
12 my $rs = $schema->resultset('Artist')->search(
15 page => 1, # page to return (defaults to 1)
16 rows => 10, # number of results per page
20 return $rs->all(); # all records for page 1
22 The C<page> attribute does not have to be specified in your search:
24 my $rs = $schema->resultset('Artist')->search(
31 return $rs->page(1); # DBIx::Class::ResultSet containing first 10 records
33 In either of the above cases, you can get a L<Data::Page> object for the
34 resultset (suitable for use in e.g. a template) using the C<pager> method:
38 =head2 Complex WHERE clauses
40 Sometimes you need to formulate a query using specific operators:
42 my @albums = $schema->resultset('Album')->search({
43 artist => { 'like', '%Lamb%' },
44 title => { 'like', '%Fear of Fours%' },
47 This results in something like the following C<WHERE> clause:
49 WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
51 Other queries might require slightly more complex logic:
53 my @albums = $schema->resultset('Album')->search({
56 artist => { 'like', '%Smashing Pumpkins%' },
57 title => 'Siamese Dream',
59 artist => 'Starchildren',
63 This results in the following C<WHERE> clause:
65 WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
66 OR artist = 'Starchildren'
68 For more information on generating complex queries, see
69 L<SQL::Abstract/WHERE CLAUSES>.
71 =head2 Arbitrary SQL through a custom ResultSource
73 Sometimes you have to run arbitrary SQL because your query is too complex
74 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
75 be optimized for your database in a special way, but you still want to
76 get the results as a L<DBIx::Class::ResultSet>.
77 The recommended way to accomplish this is by defining a separate ResultSource
78 for your query. You can then inject complete SQL statements using a scalar
79 reference (this is a feature of L<SQL::Abstract>).
81 Say you want to run a complex custom query on your user data, here's what
82 you have to add to your User class:
84 package My::Schema::User;
86 use base qw/DBIx::Class/;
88 # ->load_components, ->table, ->add_columns, etc.
90 # Make a new ResultSource based on the User class
91 my $source = __PACKAGE__->result_source_instance();
92 my $new_source = $source->new( $source );
93 $new_source->source_name( 'UserFriendsComplex' );
95 # Hand in your query as a scalar reference
96 # It will be added as a sub-select after FROM,
97 # so pay attention to the surrounding brackets!
98 $new_source->name( \<<SQL );
99 ( SELECT u.* FROM user u
100 INNER JOIN user_friends f ON u.id = f.user_id
101 WHERE f.friend_user_id = ?
103 SELECT u.* FROM user u
104 INNER JOIN user_friends f ON u.id = f.friend_user_id
105 WHERE f.user_id = ? )
108 # Finally, register your new ResultSource with your Schema
109 My::Schema->register_source( 'UserFriendsComplex' => $new_source );
111 Next, you can execute your complex query using bind parameters like this:
113 my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {},
115 bind => [ 12345, 12345 ]
119 ... and you'll get back a perfect L<DBIx::Class::ResultSet>.
121 =head2 Using specific columns
123 When you only want specific columns from a table, you can use
124 C<columns> to specify which ones you need. This is useful to avoid
125 loading columns with large amounts of data that you aren't about to
128 my $rs = $schema->resultset('Artist')->search(
131 columns => [qw/ name /]
136 # SELECT artist.name FROM artist
138 This is a shortcut for C<select> and C<as>, see below. C<columns>
139 cannot be used together with C<select> and C<as>.
141 =head2 Using database functions or stored procedures
143 The combination of C<select> and C<as> can be used to return the result of a
144 database function or stored procedure as a column value. You use C<select> to
145 specify the source for your column value (e.g. a column name, function, or
146 stored procedure name). You then use C<as> to set the column name you will use
147 to access the returned value:
149 my $rs = $schema->resultset('Artist')->search(
152 select => [ 'name', { LENGTH => 'name' } ],
153 as => [qw/ name name_length /],
158 # SELECT name name, LENGTH( name )
161 Note that the C< as > attribute has absolutely nothing to with the sql
162 syntax C< SELECT foo AS bar > (see the documentation in
163 L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
164 column in your base class (i.e. it was added with C<add_columns>), you
165 just access it as normal. Our C<Artist> class has a C<name> column, so
166 we just use the C<name> accessor:
168 my $artist = $rs->first();
169 my $name = $artist->name();
171 If on the other hand the alias does not correspond to an existing column, you
172 have to fetch the value using the C<get_column> accessor:
174 my $name_length = $artist->get_column('name_length');
176 If you don't like using C<get_column>, you can always create an accessor for
177 any of your aliases using either of these:
179 # Define accessor manually:
180 sub name_length { shift->get_column('name_length'); }
182 # Or use DBIx::Class::AccessorGroup:
183 __PACKAGE__->mk_group_accessors('column' => 'name_length');
185 =head2 SELECT DISTINCT with multiple columns
187 my $rs = $schema->resultset('Foo')->search(
191 { distinct => [ $source->columns ] }
193 as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
197 =head2 SELECT COUNT(DISTINCT colname)
199 my $rs = $schema->resultset('Foo')->search(
203 { count => { distinct => 'colname' } }
209 my $count = $rs->next->get_column('count');
211 =head2 Grouping results
213 L<DBIx::Class> supports C<GROUP BY> as follows:
215 my $rs = $schema->resultset('Artist')->search(
219 select => [ 'name', { count => 'cds.cdid' } ],
220 as => [qw/ name cd_count /],
221 group_by => [qw/ name /]
226 # SELECT name, COUNT( cds.cdid ) FROM artist me
227 # LEFT JOIN cd cds ON ( cds.artist = me.artistid )
230 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
231 are in any way unsure about the use of the attributes above (C< join
232 >, C< select >, C< as > and C< group_by >).
234 =head2 Predefined searches
236 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
237 and define often used searches as methods:
239 package My::DBIC::ResultSet::CD;
242 use base 'DBIx::Class::ResultSet';
244 sub search_cds_ordered {
247 return $self->search(
249 { order_by => 'name DESC' },
255 To use your resultset, first tell DBIx::Class to create an instance of it
256 for you, in your My::DBIC::Schema::CD class:
258 # class definition as normal
259 __PACKAGE__->load_components(qw/ Core /);
260 __PACKAGE__->table('cd');
262 # tell DBIC to use the custom ResultSet class
263 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
265 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
267 Then call your new method in your code:
269 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
271 =head2 Using SQL functions on the left hand side of a comparison
273 Using SQL functions on the left hand side of a comparison is generally
274 not a good idea since it requires a scan of the entire table. However,
275 it can be accomplished with C<DBIx::Class> when necessary.
277 If you do not have quoting on, simply include the function in your search
278 specification as you would any column:
280 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
282 With quoting on, or for a more portable solution, use the C<where>
285 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
289 (When the bind args ordering bug is fixed, this technique will be better
290 and can replace the one above.)
292 With quoting on, or for a more portable solution, use the C<where> and
296 where => \'YEAR(date_of_birth) = ?',
302 =head1 JOINS AND PREFETCHING
304 =head2 Using joins and prefetch
306 You can use the C<join> attribute to allow searching on, or sorting your
307 results by, one or more columns in a related table. To return all CDs matching
308 a particular artist name:
310 my $rs = $schema->resultset('CD')->search(
312 'artist.name' => 'Bob Marley'
315 join => [qw/artist/], # join the artist table
320 # SELECT cd.* FROM cd
321 # JOIN artist ON cd.artist = artist.id
322 # WHERE artist.name = 'Bob Marley'
324 If required, you can now sort on any column in the related tables by including
325 it in your C<order_by> attribute:
327 my $rs = $schema->resultset('CD')->search(
329 'artist.name' => 'Bob Marley'
332 join => [qw/ artist /],
333 order_by => [qw/ artist.name /]
338 # SELECT cd.* FROM cd
339 # JOIN artist ON cd.artist = artist.id
340 # WHERE artist.name = 'Bob Marley'
341 # ORDER BY artist.name
343 Note that the C<join> attribute should only be used when you need to search or
344 sort using columns in a related table. Joining related tables when you only
345 need columns from the main table will make performance worse!
347 Now let's say you want to display a list of CDs, each with the name of the
348 artist. The following will work fine:
350 while (my $cd = $rs->next) {
351 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
354 There is a problem however. We have searched both the C<cd> and C<artist> tables
355 in our main query, but we have only returned data from the C<cd> table. To get
356 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
359 SELECT artist.* FROM artist WHERE artist.id = ?
361 A statement like the one above will run for each and every CD returned by our
362 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
365 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
366 This allows you to fetch results from related tables in advance:
368 my $rs = $schema->resultset('CD')->search(
370 'artist.name' => 'Bob Marley'
373 join => [qw/ artist /],
374 order_by => [qw/ artist.name /],
375 prefetch => [qw/ artist /] # return artist data too!
379 # Equivalent SQL (note SELECT from both "cd" and "artist"):
380 # SELECT cd.*, artist.* FROM cd
381 # JOIN artist ON cd.artist = artist.id
382 # WHERE artist.name = 'Bob Marley'
383 # ORDER BY artist.name
385 The code to print the CD list remains the same:
387 while (my $cd = $rs->next) {
388 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
391 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
392 so no additional SQL statements are executed. You now have a much more
395 Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
396 C<has_many> relationships.
398 Also note that C<prefetch> should only be used when you know you will
399 definitely use data from a related table. Pre-fetching related tables when you
400 only need columns from the main table will make performance worse!
402 =head2 Multi-step joins
404 Sometimes you want to join more than one relationship deep. In this example,
405 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
406 contain a specific string:
408 # Relationships defined elsewhere:
409 # Artist->has_many('cds' => 'CD', 'artist');
410 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
412 my $rs = $schema->resultset('Artist')->search(
414 'liner_notes.notes' => { 'like', '%some text%' },
418 'cds' => 'liner_notes'
424 # SELECT artist.* FROM artist
425 # JOIN ( cd ON artist.id = cd.artist )
426 # JOIN ( liner_notes ON cd.id = liner_notes.cd )
427 # WHERE liner_notes.notes LIKE '%some text%'
429 Joins can be nested to an arbitrary level. So if we decide later that we
430 want to reduce the number of Artists returned based on who wrote the liner
433 # Relationship defined elsewhere:
434 # LinerNotes->belongs_to('author' => 'Person');
436 my $rs = $schema->resultset('Artist')->search(
438 'liner_notes.notes' => { 'like', '%some text%' },
439 'author.name' => 'A. Writer'
444 'liner_notes' => 'author'
451 # SELECT artist.* FROM artist
452 # JOIN ( cd ON artist.id = cd.artist )
453 # JOIN ( liner_notes ON cd.id = liner_notes.cd )
454 # JOIN ( author ON author.id = liner_notes.author )
455 # WHERE liner_notes.notes LIKE '%some text%'
456 # AND author.name = 'A. Writer'
458 =head2 Multi-step prefetch
460 From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
461 deep using the same syntax as a multi-step join:
463 my $rs = $schema->resultset('Tag')->search(
473 # SELECT tag.*, cd.*, artist.* FROM tag
474 # JOIN cd ON tag.cd = cd.cdid
475 # JOIN artist ON cd.artist = artist.artistid
477 Now accessing our C<cd> and C<artist> relationships does not need additional
480 my $tag = $rs->first;
481 print $tag->cd->artist->name;
483 =head1 ROW-LEVEL OPERATIONS
485 =head2 Retrieving a row object's Schema
487 It is possible to get a Schema object from a row object like so:
489 my $schema = $cd->result_source->schema;
490 # use the schema as normal:
491 my $artist_rs = $schema->resultset('Artist');
493 This can be useful when you don't want to pass around a Schema object to every
496 =head2 Getting the value of the primary key for the last database insert
498 AKA getting last_insert_id
500 If you are using PK::Auto (which is a core component as of 0.07), this is
503 my $foo = $rs->create(\%blah);
505 my $id = $foo->id; # foo->my_primary_key_field will also work.
507 If you are not using autoincrementing primary keys, this will probably
508 not work, but then you already know the value of the last primary key anyway.
510 =head2 Stringification
512 Employ the standard stringification technique by using the C<overload>
515 To make an object stringify itself as a single column, use something
516 like this (replace C<foo> with the column/method of your choice):
518 use overload '""' => sub { shift->name}, fallback => 1;
520 For more complex stringification, you can use an anonymous subroutine:
522 use overload '""' => sub { $_[0]->name . ", " .
523 $_[0]->address }, fallback => 1;
525 =head3 Stringification Example
527 Suppose we have two tables: C<Product> and C<Category>. The table
530 Product(id, Description, category)
531 Category(id, Description)
533 C<category> is a foreign key into the Category table.
535 If you have a Product object C<$obj> and write something like
539 things will not work as expected.
541 To obtain, for example, the category description, you should add this
542 method to the class defining the Category table:
544 use overload "" => sub {
547 return $self->Description;
550 =head2 Want to know if find_or_create found or created a row?
552 Just use C<find_or_new> instead, then check C<in_storage>:
554 my $obj = $rs->find_or_new({ blah => 'blarg' });
555 unless ($obj->in_storage) {
557 # do whatever else you wanted if it was a new row
560 =head2 Dynamic Sub-classing DBIx::Class proxy classes
562 AKA multi-class object inflation from one table
564 L<DBIx::Class> classes are proxy classes, therefore some different
565 techniques need to be employed for more than basic subclassing. In
566 this example we have a single user table that carries a boolean bit
567 for admin. We would like like to give the admin users
568 objects(L<DBIx::Class::Row>) the same methods as a regular user but
569 also special admin only methods. It doesn't make sense to create two
570 seperate proxy-class files for this. We would be copying all the user
571 methods into the Admin class. There is a cleaner way to accomplish
574 Overriding the C<inflate_result> method within the User proxy-class
575 gives us the effect we want. This method is called by
576 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
577 grab the object being returned, inspect the values we are looking for,
578 bless it if it's an admin object, and then return it. See the example
585 use base qw/DBIx::Class::Schema/;
587 __PACKAGE__->load_classes(qw/User/);
590 B<Proxy-Class definitions>
592 package DB::Schema::User;
596 use base qw/DBIx::Class/;
598 ### Defined what our admin class is for ensure_class_loaded
599 my $admin_class = __PACKAGE__ . '::Admin';
601 __PACKAGE__->load_components(qw/Core/);
603 __PACKAGE__->table('users');
605 __PACKAGE__->add_columns(qw/user_id email password
606 firstname lastname active
609 __PACKAGE__->set_primary_key('user_id');
613 my $ret = $self->next::method(@_);
614 if( $ret->admin ) {### If this is an admin rebless for extra functions
615 $self->ensure_class_loaded( $admin_class );
616 bless $ret, $admin_class;
622 print "I am a regular user.\n";
627 package DB::Schema::User::Admin;
631 use base qw/DB::Schema::User/;
635 print "I am an admin.\n";
641 print "I am doing admin stuff\n";
651 my $user_data = { email => 'someguy@place.com',
655 my $admin_data = { email => 'someadmin@adminplace.com',
659 my $schema = DB::Schema->connection('dbi:Pg:dbname=test');
661 $schema->resultset('User')->create( $user_data );
662 $schema->resultset('User')->create( $admin_data );
664 ### Now we search for them
665 my $user = $schema->resultset('User')->single( $user_data );
666 my $admin = $schema->resultset('User')->single( $admin_data );
668 print ref $user, "\n";
669 print ref $admin, "\n";
671 print $user->password , "\n"; # pass1
672 print $admin->password , "\n";# pass2; inherited from User
673 print $user->hello , "\n";# I am a regular user.
674 print $admin->hello, "\n";# I am an admin.
676 ### The statement below will NOT print
677 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
678 ### The statement below will print
679 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
681 =head2 Skip object creation for faster results
683 DBIx::Class is not built for speed, it's built for convenience and
684 ease of use, but sometimes you just need to get the data, and skip the
687 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
689 my $rs = $schema->resultset('CD');
691 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
693 my $hash_ref = $rs->find(1);
697 =head2 Get raw data for blindingly fast results
699 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
700 above is not fast enough for you, you can use a DBIx::Class to return values
701 exactly as they come out of the data base with none of the convenience methods
704 This is used like so:-
706 my $cursor = $rs->cursor
707 while (my @vals = $cursor->next) {
708 # use $val[0..n] here
711 You will need to map the array offsets to particular columns (you can
712 use the I<select> attribute of C<search()> to force ordering).
714 =head1 RESULTSET OPERATIONS
716 =head2 Getting Schema from a ResultSet
718 To get the schema object from a result set, do the following:
720 $rs->result_source->schema
722 =head2 Getting Columns Of Data
726 If you want to find the sum of a particular column there are several
727 ways, the obvious one is to use search:
729 my $rs = $schema->resultset('Items')->search(
732 select => [ { sum => 'Cost' } ],
733 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
736 my $tc = $rs->first->get_column('total_cost');
738 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
739 returned when you ask the C<ResultSet> for a column using
742 my $cost = $schema->resultset('Items')->get_column('Cost');
745 With this you can also do:
747 my $minvalue = $cost->min;
748 my $maxvalue = $cost->max;
750 Or just iterate through the values of this column only:
752 while ( my $c = $cost->next ) {
756 foreach my $c ($cost->all) {
760 C<ResultSetColumn> only has a limited number of built-in functions, if
761 you need one that it doesn't have, then you can use the C<func> method
764 my $avg = $cost->func('AVERAGE');
766 This will cause the following SQL statement to be run:
768 SELECT AVERAGE(Cost) FROM Items me
770 Which will of course only work if your database supports this function.
771 See L<DBIx::Class::ResultSetColumn> for more documentation.
773 =head2 Creating a result set from a set of rows
775 Sometimes you have a (set of) row objects that you want to put into a
776 resultset without the need to hit the DB again. You can do that by using the
777 L<set_cache|DBIx::Class::Resultset/set_cache> method:
779 my @uploadable_groups;
780 while (my $group = $groups->next) {
781 if ($group->can_upload($self)) {
782 push @uploadable_groups, $group;
785 my $new_rs = $self->result_source->resultset;
786 $new_rs->set_cache(\@uploadable_groups);
790 =head1 USING RELATIONSHIPS
792 =head2 Create a new row in a related table
794 my $author = $book->create_related('author', { name => 'Fred'});
796 =head2 Search in a related table
798 Only searches for books named 'Titanic' by the author in $author.
800 my $books_rs = $author->search_related('books', { name => 'Titanic' });
802 =head2 Delete data in a related table
804 Deletes only the book named Titanic by the author in $author.
806 $author->delete_related('books', { name => 'Titanic' });
808 =head2 Ordering a relationship result set
810 If you always want a relation to be ordered, you can specify this when you
811 create the relationship.
813 To order C<< $book->pages >> by descending page_number, create the relation
816 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
818 =head2 Many-to-many relationships
820 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
823 use base 'DBIx::Class';
824 __PACKAGE__->load_components('Core');
825 __PACKAGE__->table('user');
826 __PACKAGE__->add_columns(qw/id name/);
827 __PACKAGE__->set_primary_key('id');
828 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
829 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
831 package My::UserAddress;
832 use base 'DBIx::Class';
833 __PACKAGE__->load_components('Core');
834 __PACKAGE__->table('user_address');
835 __PACKAGE__->add_columns(qw/user address/);
836 __PACKAGE__->set_primary_key(qw/user address/);
837 __PACKAGE__->belongs_to('user' => 'My::User');
838 __PACKAGE__->belongs_to('address' => 'My::Address');
841 use base 'DBIx::Class';
842 __PACKAGE__->load_components('Core');
843 __PACKAGE__->table('address');
844 __PACKAGE__->add_columns(qw/id street town area_code country/);
845 __PACKAGE__->set_primary_key('id');
846 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
847 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
849 $rs = $user->addresses(); # get all addresses for a user
850 $rs = $address->users(); # get all users for an address
854 As of version 0.04001, there is improved transaction support in
855 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
856 example of the recommended way to use it:
858 my $genus = $schema->resultset('Genus')->find(12);
866 $genus->add_to_species({ name => 'troglodyte' });
869 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
870 return $genus->species;
875 $rs = $schema->txn_do($coderef1);
878 if ($@) { # Transaction failed
879 die "the sky is falling!" #
880 if ($@ =~ /Rollback failed/); # Rollback failed
882 deal_with_failed_transaction();
885 Nested transactions will work as expected. That is, only the outermost
886 transaction will actually issue a commit to the $dbh, and a rollback
887 at any level of any transaction will cause the entire nested
888 transaction to fail. Support for savepoints and for true nested
889 transactions (for databases that support them) will hopefully be added
894 =head2 Creating Schemas From An Existing Database
896 L<DBIx::Class::Schema::Loader> will connect to a database and create a
897 L<DBIx::Class::Schema> and associated sources by examining the database.
899 The recommend way of achieving this is to use the
900 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
902 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
903 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
905 This will create a tree of files rooted at C<./lib/My/Schema/> containing
906 source definitions for all the tables found in the C<foo> database.
908 =head2 Creating DDL SQL
910 The following functionality requires you to have L<SQL::Translator>
911 (also known as "SQL Fairy") installed.
913 To create a set of database-specific .sql files for the above schema:
915 my $schema = My::Schema->connect($dsn);
916 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
921 By default this will create schema files in the current directory, for
922 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
924 To create a new database using the schema:
926 my $schema = My::Schema->connect($dsn);
927 $schema->deploy({ add_drop_tables => 1});
929 To import created .sql files using the mysql client:
931 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
933 To create C<ALTER TABLE> conversion scripts to update a database to a
934 newer version of your schema at a later point, first set a new
935 C<$VERSION> in your Schema file, then:
937 my $schema = My::Schema->connect($dsn);
938 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
944 This will produce new database-specific .sql files for the new version
945 of the schema, plus scripts to convert from version 0.1 to 0.2. This
946 requires that the files for 0.1 as created above are available in the
947 given directory to diff against.
949 =head2 Select from dual
951 Dummy tables are needed by some databases to allow calling functions
952 or expressions that aren't based on table content, for examples of how
953 this applies to various database types, see:
954 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
956 Note: If you're using Oracles dual table don't B<ever> do anything
957 other than a select, if you CRUD on your dual table you *will* break
960 Make a table class as you would for any other table
962 package MyAppDB::Dual;
965 use base 'DBIx::Class';
966 __PACKAGE__->load_components("Core");
967 __PACKAGE__->table("Dual");
968 __PACKAGE__->add_columns(
970 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
973 Once you've loaded your table class select from it using C<select>
974 and C<as> instead of C<columns>
976 my $rs = $schema->resultset('Dual')->search(undef,
977 { select => [ 'sydate' ],
982 All you have to do now is be careful how you access your resultset, the below
983 will not work because there is no column called 'now' in the Dual table class
985 while (my $dual = $rs->next) {
986 print $dual->now."\n";
988 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
990 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
991 your Dual class for whatever you wanted to select from dual, but that's just
992 silly, instead use C<get_column>
994 while (my $dual = $rs->next) {
995 print $dual->get_column('now')."\n";
1000 my $cursor = $rs->cursor;
1001 while (my @vals = $cursor->next) {
1002 print $vals[0]."\n";
1005 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1007 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1008 while ( my $dual = $rs->next ) {
1009 print $dual->{now}."\n";
1012 Here are some example C<select> conditions to illustrate the different syntax
1013 you could use for doing stuff like
1014 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1016 # get a sequence value
1017 select => [ 'A_SEQ.nextval' ],
1019 # get create table sql
1020 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1022 # get a random num between 0 and 100
1023 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1026 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1029 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1031 # which day of the week were you born on?
1032 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1034 # select 16 rows from dual
1035 select => [ "'hello'" ],
1037 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1041 =head2 Adding Indexes And Functions To Your SQL
1043 Often you will want indexes on columns on your table to speed up searching. To
1044 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1047 package My::Schema::Artist;
1049 __PACKAGE__->table('artist');
1050 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1052 sub sqlt_deploy_hook {
1053 my ($self, $sqlt_table) = @_;
1055 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1060 Sometimes you might want to change the index depending on the type of the
1061 database for which SQL is being generated:
1063 my ($db_type = $sqlt_table->schema->translator->producer_type)
1064 =~ s/^SQL::Translator::Producer:://;
1066 You can also add hooks to the schema level to stop certain tables being
1073 sub sqlt_deploy_hook {
1074 my ($self, $sqlt_schema) = @_;
1076 $sqlt_schema->drop_table('table_name');
1079 You could also add views or procedures to the output using
1080 L<SQL::Translator::Schema/add_view> or
1081 L<SQL::Translator::Schema/add_procedure>.
1083 =head2 Schema versioning
1085 The following example shows simplistically how you might use DBIx::Class to
1086 deploy versioned schemas to your customers. The basic process is as follows:
1092 Create a DBIx::Class schema
1104 Modify schema to change functionality
1108 Deploy update to customers
1112 B<Create a DBIx::Class schema>
1114 This can either be done manually, or generated from an existing database as
1115 described under L</Creating Schemas From An Existing Database>
1119 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1121 B<Deploy to customers>
1123 There are several ways you could deploy your schema. These are probably
1124 beyond the scope of this recipe, but might include:
1130 Require customer to apply manually using their RDBMS.
1134 Package along with your app, making database dump/schema update/tests
1135 all part of your install.
1139 B<Modify the schema to change functionality>
1141 As your application evolves, it may be necessary to modify your schema
1142 to change functionality. Once the changes are made to your schema in
1143 DBIx::Class, export the modified schema and the conversion scripts as
1144 in L</Creating DDL SQL>.
1146 B<Deploy update to customers>
1148 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1149 Schema class. This will add a new table to your database called
1150 C<dbix_class_schema_vesion> which will keep track of which version is installed
1151 and warn if the user trys to run a newer schema version than the
1152 database thinks it has.
1154 Alternatively, you can send the conversion sql scripts to your
1157 =head2 Setting quoting for the generated SQL.
1159 If the database contains column names with spaces and/or reserved words, they
1160 need to be quoted in the SQL queries. This is done using:
1162 __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
1163 __PACKAGE__->storage->sql_maker->name_sep('.');
1165 The first sets the quote characters. Either a pair of matching
1166 brackets, or a C<"> or C<'>:
1168 __PACKAGE__->storage->sql_maker->quote_char('"');
1170 Check the documentation of your database for the correct quote
1171 characters to use. C<name_sep> needs to be set to allow the SQL
1172 generator to put the quotes the correct place.
1174 In most cases you should set these as part of the arguments passed to
1175 L<DBIx::Class::Schema/conect>:
1177 my $schema = My::Schema->connect(
1187 =head2 Setting limit dialect for SQL::Abstract::Limit
1189 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1190 the remote SQL server by looking at the database handle. This is a
1191 common problem when using the DBD::JDBC, since the DBD-driver only
1192 know that in has a Java-driver available, not which JDBC driver the
1193 Java component has loaded. This specifically sets the limit_dialect
1194 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1197 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1199 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1200 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1202 The limit dialect can also be set at connect time by specifying a
1203 C<limit_dialect> key in the final hash as shown above.
1205 =head1 BOOTSTRAPPING/MIGRATING
1207 =head2 Easy migration from class-based to schema-based setup
1209 You want to start using the schema-based approach to L<DBIx::Class>
1210 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1211 of existing classes that you don't want to move by hand. Try this nifty script
1215 use SQL::Translator;
1217 my $schema = MyDB->schema_instance;
1219 my $translator = SQL::Translator->new(
1220 debug => $debug || 0,
1221 trace => $trace || 0,
1222 no_comments => $no_comments || 0,
1223 show_warnings => $show_warnings || 0,
1224 add_drop_table => $add_drop_table || 0,
1225 validate => $validate || 0,
1227 'DBIx::Schema' => $schema,
1230 'prefix' => 'My::Schema',
1234 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1235 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1237 my $output = $translator->translate(@args) or die
1238 "Error: " . $translator->error;
1242 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1243 namespace, which is currently left as an exercise for the reader.
1245 =head1 OVERLOADING METHODS
1247 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1248 method calls, useful for things like default values and triggers. You have to
1249 use calls to C<next::method> to overload methods. More information on using
1250 L<Class::C3> with L<DBIx::Class> can be found in
1251 L<DBIx::Class::Manual::Component>.
1253 =head2 Setting default values for a row
1255 It's as simple as overriding the C<new> method. Note the use of
1259 my ( $class, $attrs ) = @_;
1261 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1263 my $new = $class->next::method($attrs);
1268 For more information about C<next::method>, look in the L<Class::C3>
1269 documentation. See also L<DBIx::Class::Manual::Component> for more
1270 ways to write your own base classes to do this.
1272 People looking for ways to do "triggers" with DBIx::Class are probably
1273 just looking for this.
1275 =head2 Changing one field whenever another changes
1277 For example, say that you have three columns, C<id>, C<number>, and
1278 C<squared>. You would like to make changes to C<number> and have
1279 C<squared> be automagically set to the value of C<number> squared.
1280 You can accomplish this by overriding C<store_column>:
1283 my ( $self, $name, $value ) = @_;
1284 if ($name eq 'number') {
1285 $self->squared($value * $value);
1287 $self->next::method($name, $value);
1290 Note that the hard work is done by the call to C<next::method>, which
1291 redispatches your call to store_column in the superclass(es).
1293 =head2 Automatically creating related objects
1295 You might have a class C<Artist> which has many C<CD>s. Further, if you
1296 want to create a C<CD> object every time you insert an C<Artist> object.
1297 You can accomplish this by overriding C<insert> on your objects:
1300 my ( $self, @args ) = @_;
1301 $self->next::method(@args);
1302 $self->cds->new({})->fill_from_artist($self)->insert;
1306 where C<fill_from_artist> is a method you specify in C<CD> which sets
1307 values in C<CD> based on the data in the C<Artist> object you pass in.
1309 =head2 Wrapping/overloading a column accessor
1313 Say you have a table "Camera" and want to associate a description
1314 with each camera. For most cameras, you'll be able to generate the description from
1315 the other columns. However, in a few special cases you may want to associate a
1316 custom description with a camera.
1320 In your database schema, define a description field in the "Camera" table that
1321 can contain text and null values.
1323 In DBIC, we'll overload the column accessor to provide a sane default if no
1324 custom description is defined. The accessor will either return or generate the
1325 description, depending on whether the field is null or not.
1327 First, in your "Camera" schema class, define the description field as follows:
1329 __PACKAGE__->add_columns(description => { accessor => '_description' });
1331 Next, we'll define the accessor-wrapper subroutine:
1336 # If there is an update to the column, we'll let the original accessor
1338 return $self->_description(@_) if @_;
1340 # Fetch the column value.
1341 my $description = $self->_description;
1343 # If there's something in the description field, then just return that.
1344 return $description if defined $description && length $descripton;
1346 # Otherwise, generate a description.
1347 return $self->generate_description;
1350 =head1 DEBUGGING AND PROFILING
1352 =head2 DBIx::Class objects with Data::Dumper
1354 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1355 be hard to find the pertinent data in all the data it can generate.
1356 Specifically, if one naively tries to use it like so,
1360 my $cd = $schema->resultset('CD')->find(1);
1363 several pages worth of data from the CD object's schema and result source will
1364 be dumped to the screen. Since usually one is only interested in a few column
1365 values of the object, this is not very helpful.
1367 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1368 it. Simply define a hook that L<Data::Dumper> will call on the object before
1369 dumping it. For example,
1376 result_source => undef,
1384 local $Data::Dumper::Freezer = '_dumper_hook';
1386 my $cd = $schema->resultset('CD')->find(1);
1388 # dumps $cd without its ResultSource
1390 If the structure of your schema is such that there is a common base class for
1391 all your table classes, simply put a method similar to C<_dumper_hook> in the
1392 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1393 will automagically clean up your data before printing it. See
1394 L<Data::Dumper/EXAMPLES> for more information.
1398 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1399 executed as well as notifications of query completion and transaction
1400 begin/commit. If you'd like to profile the SQL you can subclass the
1401 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1404 package My::Profiler;
1407 use base 'DBIx::Class::Storage::Statistics';
1409 use Time::HiRes qw(time);
1418 $self->print("Executing $sql: ".join(', ', @params)."\n");
1427 my $elapsed = sprintf("%0.4f", time() - $start);
1428 $self->print("Execution took $elapsed seconds.\n");
1434 You can then install that class as the debugging object:
1436 __PACKAGE__->storage->debugobj(new My::Profiler());
1437 __PACKAGE__->storage->debug(1);
1439 A more complicated example might involve storing each execution of SQL in an
1447 my $elapsed = time() - $start;
1448 push(@{ $calls{$sql} }, {
1454 You could then create average, high and low execution times for an SQL
1455 statement and dig down to see if certain parameters cause aberrant behavior.
1456 You might want to check out L<DBIx::Class::QueryLog> as well.