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 Retrieve one and only one row from a resultset
73 Sometimes you need only the first "top" row of a resultset. While this can be
74 easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal,
75 as a full blown cursor for the resultset will be created and then immediately
76 destroyed after fetching the first row object.
77 L<< $rs->single|DBIx::Class::ResultSet/single >> is
78 designed specifically for this case - it will grab the first returned result
79 without even instantiating a cursor.
81 Before replacing all your calls to C<first()> with C<single()> please observe the
87 While single() takes a search condition just like search() does, it does
88 _not_ accept search attributes. However one can always chain a single() to
91 my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single;
95 Since single() is the engine behind find(), it is designed to fetch a
96 single row per database query. Thus a warning will be issued when the
97 underlying SELECT returns more than one row. Sometimes however this usage
98 is valid: i.e. we have an arbitrary number of cd's but only one of them is
99 at the top of the charts at any given time. If you know what you are doing,
100 you can silence the warning by explicitly limiting the resultset size:
102 my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single;
106 =head2 Arbitrary SQL through a custom ResultSource
108 Sometimes you have to run arbitrary SQL because your query is too complex
109 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
110 be optimized for your database in a special way, but you still want to
111 get the results as a L<DBIx::Class::ResultSet>.
112 The recommended way to accomplish this is by defining a separate ResultSource
113 for your query. You can then inject complete SQL statements using a scalar
114 reference (this is a feature of L<SQL::Abstract>).
116 Say you want to run a complex custom query on your user data, here's what
117 you have to add to your User class:
119 package My::Schema::User;
121 use base qw/DBIx::Class/;
123 # ->load_components, ->table, ->add_columns, etc.
125 # Make a new ResultSource based on the User class
126 my $source = __PACKAGE__->result_source_instance();
127 my $new_source = $source->new( $source );
128 $new_source->source_name( 'UserFriendsComplex' );
130 # Hand in your query as a scalar reference
131 # It will be added as a sub-select after FROM,
132 # so pay attention to the surrounding brackets!
133 $new_source->name( \<<SQL );
134 ( SELECT u.* FROM user u
135 INNER JOIN user_friends f ON u.id = f.user_id
136 WHERE f.friend_user_id = ?
138 SELECT u.* FROM user u
139 INNER JOIN user_friends f ON u.id = f.friend_user_id
140 WHERE f.user_id = ? )
143 # Finally, register your new ResultSource with your Schema
144 My::Schema->register_source( 'UserFriendsComplex' => $new_source );
146 Next, you can execute your complex query using bind parameters like this:
148 my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {},
150 bind => [ 12345, 12345 ]
154 ... and you'll get back a perfect L<DBIx::Class::ResultSet>.
156 =head2 Using specific columns
158 When you only want specific columns from a table, you can use
159 C<columns> to specify which ones you need. This is useful to avoid
160 loading columns with large amounts of data that you aren't about to
163 my $rs = $schema->resultset('Artist')->search(
166 columns => [qw/ name /]
171 # SELECT artist.name FROM artist
173 This is a shortcut for C<select> and C<as>, see below. C<columns>
174 cannot be used together with C<select> and C<as>.
176 =head2 Using database functions or stored procedures
178 The combination of C<select> and C<as> can be used to return the result of a
179 database function or stored procedure as a column value. You use C<select> to
180 specify the source for your column value (e.g. a column name, function, or
181 stored procedure name). You then use C<as> to set the column name you will use
182 to access the returned value:
184 my $rs = $schema->resultset('Artist')->search(
187 select => [ 'name', { LENGTH => 'name' } ],
188 as => [qw/ name name_length /],
193 # SELECT name name, LENGTH( name )
196 Note that the C< as > attribute has absolutely nothing to with the sql
197 syntax C< SELECT foo AS bar > (see the documentation in
198 L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
199 column in your base class (i.e. it was added with C<add_columns>), you
200 just access it as normal. Our C<Artist> class has a C<name> column, so
201 we just use the C<name> accessor:
203 my $artist = $rs->first();
204 my $name = $artist->name();
206 If on the other hand the alias does not correspond to an existing column, you
207 have to fetch the value using the C<get_column> accessor:
209 my $name_length = $artist->get_column('name_length');
211 If you don't like using C<get_column>, you can always create an accessor for
212 any of your aliases using either of these:
214 # Define accessor manually:
215 sub name_length { shift->get_column('name_length'); }
217 # Or use DBIx::Class::AccessorGroup:
218 __PACKAGE__->mk_group_accessors('column' => 'name_length');
220 =head2 SELECT DISTINCT with multiple columns
222 my $rs = $schema->resultset('Foo')->search(
226 { distinct => [ $source->columns ] }
228 as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
232 =head2 SELECT COUNT(DISTINCT colname)
234 my $rs = $schema->resultset('Foo')->search(
238 { count => { distinct => 'colname' } }
244 my $count = $rs->next->get_column('count');
246 =head2 Grouping results
248 L<DBIx::Class> supports C<GROUP BY> as follows:
250 my $rs = $schema->resultset('Artist')->search(
254 select => [ 'name', { count => 'cds.id' } ],
255 as => [qw/ name cd_count /],
256 group_by => [qw/ name /]
261 # SELECT name, COUNT( cd.id ) FROM artist
262 # LEFT JOIN cd ON artist.id = cd.artist
265 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
266 are in any way unsure about the use of the attributes above (C< join
267 >, C< select >, C< as > and C< group_by >).
269 =head2 Predefined searches
271 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
272 and define often used searches as methods:
274 package My::DBIC::ResultSet::CD;
277 use base 'DBIx::Class::ResultSet';
279 sub search_cds_ordered {
282 return $self->search(
284 { order_by => 'name DESC' },
290 To use your resultset, first tell DBIx::Class to create an instance of it
291 for you, in your My::DBIC::Schema::CD class:
293 # class definition as normal
294 __PACKAGE__->load_components(qw/ Core /);
295 __PACKAGE__->table('cd');
297 # tell DBIC to use the custom ResultSet class
298 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
300 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
302 Then call your new method in your code:
304 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
306 =head2 Using SQL functions on the left hand side of a comparison
308 Using SQL functions on the left hand side of a comparison is generally
309 not a good idea since it requires a scan of the entire table. However,
310 it can be accomplished with C<DBIx::Class> when necessary.
312 If you do not have quoting on, simply include the function in your search
313 specification as you would any column:
315 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
317 With quoting on, or for a more portable solution, use the C<where>
320 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
324 (When the bind args ordering bug is fixed, this technique will be better
325 and can replace the one above.)
327 With quoting on, or for a more portable solution, use the C<where> and
331 where => \'YEAR(date_of_birth) = ?',
337 =head1 JOINS AND PREFETCHING
339 =head2 Using joins and prefetch
341 You can use the C<join> attribute to allow searching on, or sorting your
342 results by, one or more columns in a related table. To return all CDs matching
343 a particular artist name:
345 my $rs = $schema->resultset('CD')->search(
347 'artist.name' => 'Bob Marley'
350 join => 'artist', # join the artist table
355 # SELECT cd.* FROM cd
356 # JOIN artist ON cd.artist = artist.id
357 # WHERE artist.name = 'Bob Marley'
359 If required, you can now sort on any column in the related tables by including
360 it in your C<order_by> attribute:
362 my $rs = $schema->resultset('CD')->search(
364 'artist.name' => 'Bob Marley'
368 order_by => [qw/ artist.name /]
373 # SELECT cd.* FROM cd
374 # JOIN artist ON cd.artist = artist.id
375 # WHERE artist.name = 'Bob Marley'
376 # ORDER BY artist.name
378 Note that the C<join> attribute should only be used when you need to search or
379 sort using columns in a related table. Joining related tables when you only
380 need columns from the main table will make performance worse!
382 Now let's say you want to display a list of CDs, each with the name of the
383 artist. The following will work fine:
385 while (my $cd = $rs->next) {
386 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
389 There is a problem however. We have searched both the C<cd> and C<artist> tables
390 in our main query, but we have only returned data from the C<cd> table. To get
391 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
394 SELECT artist.* FROM artist WHERE artist.id = ?
396 A statement like the one above will run for each and every CD returned by our
397 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
400 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
401 This allows you to fetch results from related tables in advance:
403 my $rs = $schema->resultset('CD')->search(
405 'artist.name' => 'Bob Marley'
409 order_by => [qw/ artist.name /],
410 prefetch => 'artist' # return artist data too!
414 # Equivalent SQL (note SELECT from both "cd" and "artist"):
415 # SELECT cd.*, artist.* FROM cd
416 # JOIN artist ON cd.artist = artist.id
417 # WHERE artist.name = 'Bob Marley'
418 # ORDER BY artist.name
420 The code to print the CD list remains the same:
422 while (my $cd = $rs->next) {
423 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
426 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
427 so no additional SQL statements are executed. You now have a much more
430 Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
431 C<has_many> relationships.
433 Also note that C<prefetch> should only be used when you know you will
434 definitely use data from a related table. Pre-fetching related tables when you
435 only need columns from the main table will make performance worse!
437 =head2 Multiple joins
439 In the examples above, the C<join> attribute was a scalar. If you
440 pass an array reference instead, you can join to multiple tables. In
441 this example, we want to limit the search further, using
444 # Relationships defined elsewhere:
445 # CD->belongs_to('artist' => 'Artist');
446 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
447 my $rs = $schema->resultset('CD')->search(
449 'artist.name' => 'Bob Marley'
450 'liner_notes.notes' => { 'like', '%some text%' },
453 join => [qw/ artist liner_notes /],
454 order_by => [qw/ artist.name /],
459 # SELECT cd.*, artist.*, liner_notes.* FROM cd
460 # JOIN artist ON cd.artist = artist.id
461 # JOIN liner_notes ON cd.id = liner_notes.cd
462 # WHERE artist.name = 'Bob Marley'
463 # ORDER BY artist.name
465 =head2 Multi-step joins
467 Sometimes you want to join more than one relationship deep. In this example,
468 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
469 contain a specific string:
471 # Relationships defined elsewhere:
472 # Artist->has_many('cds' => 'CD', 'artist');
473 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
475 my $rs = $schema->resultset('Artist')->search(
477 'liner_notes.notes' => { 'like', '%some text%' },
481 'cds' => 'liner_notes'
487 # SELECT artist.* FROM artist
488 # LEFT JOIN cd ON artist.id = cd.artist
489 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
490 # WHERE liner_notes.notes LIKE '%some text%'
492 Joins can be nested to an arbitrary level. So if we decide later that we
493 want to reduce the number of Artists returned based on who wrote the liner
496 # Relationship defined elsewhere:
497 # LinerNotes->belongs_to('author' => 'Person');
499 my $rs = $schema->resultset('Artist')->search(
501 'liner_notes.notes' => { 'like', '%some text%' },
502 'author.name' => 'A. Writer'
507 'liner_notes' => 'author'
514 # SELECT artist.* FROM artist
515 # LEFT JOIN cd ON artist.id = cd.artist
516 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
517 # LEFT JOIN author ON author.id = liner_notes.author
518 # WHERE liner_notes.notes LIKE '%some text%'
519 # AND author.name = 'A. Writer'
521 =head2 Multi-step and multiple joins
523 With various combinations of array and hash references, you can join
524 tables in any combination you desire. For example, to join Artist to
525 CD and Concert, and join CD to LinerNotes:
527 # Relationships defined elsewhere:
528 # Artist->has_many('concerts' => 'Concert', 'artist');
530 my $rs = $schema->resultset('Artist')->search(
543 # SELECT artist.* FROM artist
544 # LEFT JOIN cd ON artist.id = cd.artist
545 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
546 # LEFT JOIN concert ON artist.id = concert.artist
548 =head2 Multi-step prefetch
550 From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
551 deep using the same syntax as a multi-step join:
553 my $rs = $schema->resultset('Tag')->search(
563 # SELECT tag.*, cd.*, artist.* FROM tag
564 # JOIN cd ON tag.cd = cd.id
565 # JOIN artist ON cd.artist = artist.id
567 Now accessing our C<cd> and C<artist> relationships does not need additional
570 my $tag = $rs->first;
571 print $tag->cd->artist->name;
573 =head1 ROW-LEVEL OPERATIONS
575 =head2 Retrieving a row object's Schema
577 It is possible to get a Schema object from a row object like so:
579 my $schema = $cd->result_source->schema;
580 # use the schema as normal:
581 my $artist_rs = $schema->resultset('Artist');
583 This can be useful when you don't want to pass around a Schema object to every
586 =head2 Getting the value of the primary key for the last database insert
588 AKA getting last_insert_id
590 If you are using PK::Auto (which is a core component as of 0.07), this is
593 my $foo = $rs->create(\%blah);
595 my $id = $foo->id; # foo->my_primary_key_field will also work.
597 If you are not using autoincrementing primary keys, this will probably
598 not work, but then you already know the value of the last primary key anyway.
600 =head2 Stringification
602 Employ the standard stringification technique by using the C<overload>
605 To make an object stringify itself as a single column, use something
606 like this (replace C<foo> with the column/method of your choice):
608 use overload '""' => sub { shift->name}, fallback => 1;
610 For more complex stringification, you can use an anonymous subroutine:
612 use overload '""' => sub { $_[0]->name . ", " .
613 $_[0]->address }, fallback => 1;
615 =head3 Stringification Example
617 Suppose we have two tables: C<Product> and C<Category>. The table
620 Product(id, Description, category)
621 Category(id, Description)
623 C<category> is a foreign key into the Category table.
625 If you have a Product object C<$obj> and write something like
629 things will not work as expected.
631 To obtain, for example, the category description, you should add this
632 method to the class defining the Category table:
634 use overload "" => sub {
637 return $self->Description;
640 =head2 Want to know if find_or_create found or created a row?
642 Just use C<find_or_new> instead, then check C<in_storage>:
644 my $obj = $rs->find_or_new({ blah => 'blarg' });
645 unless ($obj->in_storage) {
647 # do whatever else you wanted if it was a new row
650 =head2 Dynamic Sub-classing DBIx::Class proxy classes
652 AKA multi-class object inflation from one table
654 L<DBIx::Class> classes are proxy classes, therefore some different
655 techniques need to be employed for more than basic subclassing. In
656 this example we have a single user table that carries a boolean bit
657 for admin. We would like like to give the admin users
658 objects(L<DBIx::Class::Row>) the same methods as a regular user but
659 also special admin only methods. It doesn't make sense to create two
660 seperate proxy-class files for this. We would be copying all the user
661 methods into the Admin class. There is a cleaner way to accomplish
664 Overriding the C<inflate_result> method within the User proxy-class
665 gives us the effect we want. This method is called by
666 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
667 grab the object being returned, inspect the values we are looking for,
668 bless it if it's an admin object, and then return it. See the example
675 use base qw/DBIx::Class::Schema/;
677 __PACKAGE__->load_classes(qw/User/);
680 B<Proxy-Class definitions>
682 package DB::Schema::User;
686 use base qw/DBIx::Class/;
688 ### Defined what our admin class is for ensure_class_loaded
689 my $admin_class = __PACKAGE__ . '::Admin';
691 __PACKAGE__->load_components(qw/Core/);
693 __PACKAGE__->table('users');
695 __PACKAGE__->add_columns(qw/user_id email password
696 firstname lastname active
699 __PACKAGE__->set_primary_key('user_id');
703 my $ret = $self->next::method(@_);
704 if( $ret->admin ) {### If this is an admin rebless for extra functions
705 $self->ensure_class_loaded( $admin_class );
706 bless $ret, $admin_class;
712 print "I am a regular user.\n";
717 package DB::Schema::User::Admin;
721 use base qw/DB::Schema::User/;
725 print "I am an admin.\n";
731 print "I am doing admin stuff\n";
741 my $user_data = { email => 'someguy@place.com',
745 my $admin_data = { email => 'someadmin@adminplace.com',
749 my $schema = DB::Schema->connection('dbi:Pg:dbname=test');
751 $schema->resultset('User')->create( $user_data );
752 $schema->resultset('User')->create( $admin_data );
754 ### Now we search for them
755 my $user = $schema->resultset('User')->single( $user_data );
756 my $admin = $schema->resultset('User')->single( $admin_data );
758 print ref $user, "\n";
759 print ref $admin, "\n";
761 print $user->password , "\n"; # pass1
762 print $admin->password , "\n";# pass2; inherited from User
763 print $user->hello , "\n";# I am a regular user.
764 print $admin->hello, "\n";# I am an admin.
766 ### The statement below will NOT print
767 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
768 ### The statement below will print
769 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
771 =head2 Skip row object creation for faster results
773 DBIx::Class is not built for speed, it's built for convenience and
774 ease of use, but sometimes you just need to get the data, and skip the
777 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
779 my $rs = $schema->resultset('CD');
781 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
783 my $hash_ref = $rs->find(1);
787 =head2 Get raw data for blindingly fast results
789 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
790 above is not fast enough for you, you can use a DBIx::Class to return values
791 exactly as they come out of the data base with none of the convenience methods
794 This is used like so:-
796 my $cursor = $rs->cursor
797 while (my @vals = $cursor->next) {
798 # use $val[0..n] here
801 You will need to map the array offsets to particular columns (you can
802 use the I<select> attribute of C<search()> to force ordering).
804 =head1 RESULTSET OPERATIONS
806 =head2 Getting Schema from a ResultSet
808 To get the schema object from a result set, do the following:
810 $rs->result_source->schema
812 =head2 Getting Columns Of Data
816 If you want to find the sum of a particular column there are several
817 ways, the obvious one is to use search:
819 my $rs = $schema->resultset('Items')->search(
822 select => [ { sum => 'Cost' } ],
823 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
826 my $tc = $rs->first->get_column('total_cost');
828 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
829 returned when you ask the C<ResultSet> for a column using
832 my $cost = $schema->resultset('Items')->get_column('Cost');
835 With this you can also do:
837 my $minvalue = $cost->min;
838 my $maxvalue = $cost->max;
840 Or just iterate through the values of this column only:
842 while ( my $c = $cost->next ) {
846 foreach my $c ($cost->all) {
850 C<ResultSetColumn> only has a limited number of built-in functions, if
851 you need one that it doesn't have, then you can use the C<func> method
854 my $avg = $cost->func('AVERAGE');
856 This will cause the following SQL statement to be run:
858 SELECT AVERAGE(Cost) FROM Items me
860 Which will of course only work if your database supports this function.
861 See L<DBIx::Class::ResultSetColumn> for more documentation.
863 =head2 Creating a result set from a set of rows
865 Sometimes you have a (set of) row objects that you want to put into a
866 resultset without the need to hit the DB again. You can do that by using the
867 L<set_cache|DBIx::Class::Resultset/set_cache> method:
869 my @uploadable_groups;
870 while (my $group = $groups->next) {
871 if ($group->can_upload($self)) {
872 push @uploadable_groups, $group;
875 my $new_rs = $self->result_source->resultset;
876 $new_rs->set_cache(\@uploadable_groups);
880 =head1 USING RELATIONSHIPS
882 =head2 Create a new row in a related table
884 my $author = $book->create_related('author', { name => 'Fred'});
886 =head2 Search in a related table
888 Only searches for books named 'Titanic' by the author in $author.
890 my $books_rs = $author->search_related('books', { name => 'Titanic' });
892 =head2 Delete data in a related table
894 Deletes only the book named Titanic by the author in $author.
896 $author->delete_related('books', { name => 'Titanic' });
898 =head2 Ordering a relationship result set
900 If you always want a relation to be ordered, you can specify this when you
901 create the relationship.
903 To order C<< $book->pages >> by descending page_number, create the relation
906 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
908 =head2 Many-to-many relationships
910 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
913 use base 'DBIx::Class';
914 __PACKAGE__->load_components('Core');
915 __PACKAGE__->table('user');
916 __PACKAGE__->add_columns(qw/id name/);
917 __PACKAGE__->set_primary_key('id');
918 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
919 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
921 package My::UserAddress;
922 use base 'DBIx::Class';
923 __PACKAGE__->load_components('Core');
924 __PACKAGE__->table('user_address');
925 __PACKAGE__->add_columns(qw/user address/);
926 __PACKAGE__->set_primary_key(qw/user address/);
927 __PACKAGE__->belongs_to('user' => 'My::User');
928 __PACKAGE__->belongs_to('address' => 'My::Address');
931 use base 'DBIx::Class';
932 __PACKAGE__->load_components('Core');
933 __PACKAGE__->table('address');
934 __PACKAGE__->add_columns(qw/id street town area_code country/);
935 __PACKAGE__->set_primary_key('id');
936 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
937 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
939 $rs = $user->addresses(); # get all addresses for a user
940 $rs = $address->users(); # get all users for an address
944 As of version 0.04001, there is improved transaction support in
945 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
946 example of the recommended way to use it:
948 my $genus = $schema->resultset('Genus')->find(12);
956 $genus->add_to_species({ name => 'troglodyte' });
959 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
960 return $genus->species;
965 $rs = $schema->txn_do($coderef1);
968 if ($@) { # Transaction failed
969 die "the sky is falling!" #
970 if ($@ =~ /Rollback failed/); # Rollback failed
972 deal_with_failed_transaction();
975 Nested transactions will work as expected. That is, only the outermost
976 transaction will actually issue a commit to the $dbh, and a rollback
977 at any level of any transaction will cause the entire nested
978 transaction to fail. Support for savepoints and for true nested
979 transactions (for databases that support them) will hopefully be added
984 =head2 Creating Schemas From An Existing Database
986 L<DBIx::Class::Schema::Loader> will connect to a database and create a
987 L<DBIx::Class::Schema> and associated sources by examining the database.
989 The recommend way of achieving this is to use the
990 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
992 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
993 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
995 This will create a tree of files rooted at C<./lib/My/Schema/> containing
996 source definitions for all the tables found in the C<foo> database.
998 =head2 Creating DDL SQL
1000 The following functionality requires you to have L<SQL::Translator>
1001 (also known as "SQL Fairy") installed.
1003 To create a set of database-specific .sql files for the above schema:
1005 my $schema = My::Schema->connect($dsn);
1006 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1011 By default this will create schema files in the current directory, for
1012 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1014 To create a new database using the schema:
1016 my $schema = My::Schema->connect($dsn);
1017 $schema->deploy({ add_drop_tables => 1});
1019 To import created .sql files using the mysql client:
1021 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1023 To create C<ALTER TABLE> conversion scripts to update a database to a
1024 newer version of your schema at a later point, first set a new
1025 C<$VERSION> in your Schema file, then:
1027 my $schema = My::Schema->connect($dsn);
1028 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1034 This will produce new database-specific .sql files for the new version
1035 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1036 requires that the files for 0.1 as created above are available in the
1037 given directory to diff against.
1039 =head2 Select from dual
1041 Dummy tables are needed by some databases to allow calling functions
1042 or expressions that aren't based on table content, for examples of how
1043 this applies to various database types, see:
1044 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1046 Note: If you're using Oracles dual table don't B<ever> do anything
1047 other than a select, if you CRUD on your dual table you *will* break
1050 Make a table class as you would for any other table
1052 package MyAppDB::Dual;
1055 use base 'DBIx::Class';
1056 __PACKAGE__->load_components("Core");
1057 __PACKAGE__->table("Dual");
1058 __PACKAGE__->add_columns(
1060 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1063 Once you've loaded your table class select from it using C<select>
1064 and C<as> instead of C<columns>
1066 my $rs = $schema->resultset('Dual')->search(undef,
1067 { select => [ 'sydate' ],
1072 All you have to do now is be careful how you access your resultset, the below
1073 will not work because there is no column called 'now' in the Dual table class
1075 while (my $dual = $rs->next) {
1076 print $dual->now."\n";
1078 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1080 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1081 your Dual class for whatever you wanted to select from dual, but that's just
1082 silly, instead use C<get_column>
1084 while (my $dual = $rs->next) {
1085 print $dual->get_column('now')."\n";
1090 my $cursor = $rs->cursor;
1091 while (my @vals = $cursor->next) {
1092 print $vals[0]."\n";
1095 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1097 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1098 while ( my $dual = $rs->next ) {
1099 print $dual->{now}."\n";
1102 Here are some example C<select> conditions to illustrate the different syntax
1103 you could use for doing stuff like
1104 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1106 # get a sequence value
1107 select => [ 'A_SEQ.nextval' ],
1109 # get create table sql
1110 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1112 # get a random num between 0 and 100
1113 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1116 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1119 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1121 # which day of the week were you born on?
1122 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1124 # select 16 rows from dual
1125 select => [ "'hello'" ],
1127 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1131 =head2 Adding Indexes And Functions To Your SQL
1133 Often you will want indexes on columns on your table to speed up searching. To
1134 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1137 package My::Schema::Artist;
1139 __PACKAGE__->table('artist');
1140 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1142 sub sqlt_deploy_hook {
1143 my ($self, $sqlt_table) = @_;
1145 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1150 Sometimes you might want to change the index depending on the type of the
1151 database for which SQL is being generated:
1153 my ($db_type = $sqlt_table->schema->translator->producer_type)
1154 =~ s/^SQL::Translator::Producer:://;
1156 You can also add hooks to the schema level to stop certain tables being
1163 sub sqlt_deploy_hook {
1164 my ($self, $sqlt_schema) = @_;
1166 $sqlt_schema->drop_table('table_name');
1169 You could also add views or procedures to the output using
1170 L<SQL::Translator::Schema/add_view> or
1171 L<SQL::Translator::Schema/add_procedure>.
1173 =head2 Schema versioning
1175 The following example shows simplistically how you might use DBIx::Class to
1176 deploy versioned schemas to your customers. The basic process is as follows:
1182 Create a DBIx::Class schema
1194 Modify schema to change functionality
1198 Deploy update to customers
1202 B<Create a DBIx::Class schema>
1204 This can either be done manually, or generated from an existing database as
1205 described under L</Creating Schemas From An Existing Database>
1209 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1211 B<Deploy to customers>
1213 There are several ways you could deploy your schema. These are probably
1214 beyond the scope of this recipe, but might include:
1220 Require customer to apply manually using their RDBMS.
1224 Package along with your app, making database dump/schema update/tests
1225 all part of your install.
1229 B<Modify the schema to change functionality>
1231 As your application evolves, it may be necessary to modify your schema
1232 to change functionality. Once the changes are made to your schema in
1233 DBIx::Class, export the modified schema and the conversion scripts as
1234 in L</Creating DDL SQL>.
1236 B<Deploy update to customers>
1238 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1239 Schema class. This will add a new table to your database called
1240 C<dbix_class_schema_vesion> which will keep track of which version is installed
1241 and warn if the user trys to run a newer schema version than the
1242 database thinks it has.
1244 Alternatively, you can send the conversion sql scripts to your
1247 =head2 Setting quoting for the generated SQL.
1249 If the database contains column names with spaces and/or reserved words, they
1250 need to be quoted in the SQL queries. This is done using:
1252 __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
1253 __PACKAGE__->storage->sql_maker->name_sep('.');
1255 The first sets the quote characters. Either a pair of matching
1256 brackets, or a C<"> or C<'>:
1258 __PACKAGE__->storage->sql_maker->quote_char('"');
1260 Check the documentation of your database for the correct quote
1261 characters to use. C<name_sep> needs to be set to allow the SQL
1262 generator to put the quotes the correct place.
1264 In most cases you should set these as part of the arguments passed to
1265 L<DBIx::Class::Schema/conect>:
1267 my $schema = My::Schema->connect(
1277 =head2 Setting limit dialect for SQL::Abstract::Limit
1279 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1280 the remote SQL server by looking at the database handle. This is a
1281 common problem when using the DBD::JDBC, since the DBD-driver only
1282 know that in has a Java-driver available, not which JDBC driver the
1283 Java component has loaded. This specifically sets the limit_dialect
1284 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1287 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1289 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1290 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1292 The limit dialect can also be set at connect time by specifying a
1293 C<limit_dialect> key in the final hash as shown above.
1295 =head1 BOOTSTRAPPING/MIGRATING
1297 =head2 Easy migration from class-based to schema-based setup
1299 You want to start using the schema-based approach to L<DBIx::Class>
1300 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1301 of existing classes that you don't want to move by hand. Try this nifty script
1305 use SQL::Translator;
1307 my $schema = MyDB->schema_instance;
1309 my $translator = SQL::Translator->new(
1310 debug => $debug || 0,
1311 trace => $trace || 0,
1312 no_comments => $no_comments || 0,
1313 show_warnings => $show_warnings || 0,
1314 add_drop_table => $add_drop_table || 0,
1315 validate => $validate || 0,
1317 'DBIx::Schema' => $schema,
1320 'prefix' => 'My::Schema',
1324 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1325 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1327 my $output = $translator->translate(@args) or die
1328 "Error: " . $translator->error;
1332 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1333 namespace, which is currently left as an exercise for the reader.
1335 =head1 OVERLOADING METHODS
1337 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1338 method calls, useful for things like default values and triggers. You have to
1339 use calls to C<next::method> to overload methods. More information on using
1340 L<Class::C3> with L<DBIx::Class> can be found in
1341 L<DBIx::Class::Manual::Component>.
1343 =head2 Setting default values for a row
1345 It's as simple as overriding the C<new> method. Note the use of
1349 my ( $class, $attrs ) = @_;
1351 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1353 my $new = $class->next::method($attrs);
1358 For more information about C<next::method>, look in the L<Class::C3>
1359 documentation. See also L<DBIx::Class::Manual::Component> for more
1360 ways to write your own base classes to do this.
1362 People looking for ways to do "triggers" with DBIx::Class are probably
1363 just looking for this.
1365 =head2 Changing one field whenever another changes
1367 For example, say that you have three columns, C<id>, C<number>, and
1368 C<squared>. You would like to make changes to C<number> and have
1369 C<squared> be automagically set to the value of C<number> squared.
1370 You can accomplish this by overriding C<store_column>:
1373 my ( $self, $name, $value ) = @_;
1374 if ($name eq 'number') {
1375 $self->squared($value * $value);
1377 $self->next::method($name, $value);
1380 Note that the hard work is done by the call to C<next::method>, which
1381 redispatches your call to store_column in the superclass(es).
1383 =head2 Automatically creating related objects
1385 You might have a class C<Artist> which has many C<CD>s. Further, if you
1386 want to create a C<CD> object every time you insert an C<Artist> object.
1387 You can accomplish this by overriding C<insert> on your objects:
1390 my ( $self, @args ) = @_;
1391 $self->next::method(@args);
1392 $self->cds->new({})->fill_from_artist($self)->insert;
1396 where C<fill_from_artist> is a method you specify in C<CD> which sets
1397 values in C<CD> based on the data in the C<Artist> object you pass in.
1399 =head2 Wrapping/overloading a column accessor
1403 Say you have a table "Camera" and want to associate a description
1404 with each camera. For most cameras, you'll be able to generate the description from
1405 the other columns. However, in a few special cases you may want to associate a
1406 custom description with a camera.
1410 In your database schema, define a description field in the "Camera" table that
1411 can contain text and null values.
1413 In DBIC, we'll overload the column accessor to provide a sane default if no
1414 custom description is defined. The accessor will either return or generate the
1415 description, depending on whether the field is null or not.
1417 First, in your "Camera" schema class, define the description field as follows:
1419 __PACKAGE__->add_columns(description => { accessor => '_description' });
1421 Next, we'll define the accessor-wrapper subroutine:
1426 # If there is an update to the column, we'll let the original accessor
1428 return $self->_description(@_) if @_;
1430 # Fetch the column value.
1431 my $description = $self->_description;
1433 # If there's something in the description field, then just return that.
1434 return $description if defined $description && length $descripton;
1436 # Otherwise, generate a description.
1437 return $self->generate_description;
1440 =head1 DEBUGGING AND PROFILING
1442 =head2 DBIx::Class objects with Data::Dumper
1444 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1445 be hard to find the pertinent data in all the data it can generate.
1446 Specifically, if one naively tries to use it like so,
1450 my $cd = $schema->resultset('CD')->find(1);
1453 several pages worth of data from the CD object's schema and result source will
1454 be dumped to the screen. Since usually one is only interested in a few column
1455 values of the object, this is not very helpful.
1457 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1458 it. Simply define a hook that L<Data::Dumper> will call on the object before
1459 dumping it. For example,
1466 result_source => undef,
1474 local $Data::Dumper::Freezer = '_dumper_hook';
1476 my $cd = $schema->resultset('CD')->find(1);
1478 # dumps $cd without its ResultSource
1480 If the structure of your schema is such that there is a common base class for
1481 all your table classes, simply put a method similar to C<_dumper_hook> in the
1482 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1483 will automagically clean up your data before printing it. See
1484 L<Data::Dumper/EXAMPLES> for more information.
1488 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1489 executed as well as notifications of query completion and transaction
1490 begin/commit. If you'd like to profile the SQL you can subclass the
1491 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1494 package My::Profiler;
1497 use base 'DBIx::Class::Storage::Statistics';
1499 use Time::HiRes qw(time);
1508 $self->print("Executing $sql: ".join(', ', @params)."\n");
1517 my $elapsed = sprintf("%0.4f", time() - $start);
1518 $self->print("Execution took $elapsed seconds.\n");
1524 You can then install that class as the debugging object:
1526 __PACKAGE__->storage->debugobj(new My::Profiler());
1527 __PACKAGE__->storage->debug(1);
1529 A more complicated example might involve storing each execution of SQL in an
1537 my $elapsed = time() - $start;
1538 push(@{ $calls{$sql} }, {
1544 You could then create average, high and low execution times for an SQL
1545 statement and dig down to see if certain parameters cause aberrant behavior.
1546 You might want to check out L<DBIx::Class::QueryLog> as well.