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_extra_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> (except, of course,
155 that you cannot modify the rows it contains, ie. cannot call L</update>,
156 L</delete>, ... on it).
158 If you prefer to have the definitions of these custom ResultSources in separate
159 files (instead of stuffing all of them into the same resultset class), you can
160 achieve the same with subclassing the resultset class and defining the
163 package My::Schema::UserFriendsComplex;
165 use My::Schema::User;
166 use base qw/My::Schema::User/;
168 __PACKAGE__->table('dummy'); # currently must be called before anything else
170 # Hand in your query as a scalar reference
171 # It will be added as a sub-select after FROM,
172 # so pay attention to the surrounding brackets!
173 __PACKAGE__->name( \<<SQL );
174 ( SELECT u.* FROM user u
175 INNER JOIN user_friends f ON u.id = f.user_id
176 WHERE f.friend_user_id = ?
178 SELECT u.* FROM user u
179 INNER JOIN user_friends f ON u.id = f.friend_user_id
180 WHERE f.user_id = ? )
185 =head2 Using specific columns
187 When you only want specific columns from a table, you can use
188 C<columns> to specify which ones you need. This is useful to avoid
189 loading columns with large amounts of data that you aren't about to
192 my $rs = $schema->resultset('Artist')->search(
195 columns => [qw/ name /]
200 # SELECT artist.name FROM artist
202 This is a shortcut for C<select> and C<as>, see below. C<columns>
203 cannot be used together with C<select> and C<as>.
205 =head2 Using database functions or stored procedures
207 The combination of C<select> and C<as> can be used to return the result of a
208 database function or stored procedure as a column value. You use C<select> to
209 specify the source for your column value (e.g. a column name, function, or
210 stored procedure name). You then use C<as> to set the column name you will use
211 to access the returned value:
213 my $rs = $schema->resultset('Artist')->search(
216 select => [ 'name', { LENGTH => 'name' } ],
217 as => [qw/ name name_length /],
222 # SELECT name name, LENGTH( name )
225 Note that the C< as > attribute has absolutely nothing to with the sql
226 syntax C< SELECT foo AS bar > (see the documentation in
227 L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
228 column in your base class (i.e. it was added with C<add_columns>), you
229 just access it as normal. Our C<Artist> class has a C<name> column, so
230 we just use the C<name> accessor:
232 my $artist = $rs->first();
233 my $name = $artist->name();
235 If on the other hand the alias does not correspond to an existing column, you
236 have to fetch the value using the C<get_column> accessor:
238 my $name_length = $artist->get_column('name_length');
240 If you don't like using C<get_column>, you can always create an accessor for
241 any of your aliases using either of these:
243 # Define accessor manually:
244 sub name_length { shift->get_column('name_length'); }
246 # Or use DBIx::Class::AccessorGroup:
247 __PACKAGE__->mk_group_accessors('column' => 'name_length');
249 =head2 SELECT DISTINCT with multiple columns
251 my $rs = $schema->resultset('Foo')->search(
255 { distinct => [ $source->columns ] }
257 as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
261 =head2 SELECT COUNT(DISTINCT colname)
263 my $rs = $schema->resultset('Foo')->search(
267 { count => { distinct => 'colname' } }
273 my $count = $rs->next->get_column('count');
275 =head2 Grouping results
277 L<DBIx::Class> supports C<GROUP BY> as follows:
279 my $rs = $schema->resultset('Artist')->search(
283 select => [ 'name', { count => 'cds.id' } ],
284 as => [qw/ name cd_count /],
285 group_by => [qw/ name /]
290 # SELECT name, COUNT( cd.id ) FROM artist
291 # LEFT JOIN cd ON artist.id = cd.artist
294 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
295 are in any way unsure about the use of the attributes above (C< join
296 >, C< select >, C< as > and C< group_by >).
300 You can write subqueries relatively easily in DBIC.
302 my $inside_rs = $schema->resultset('Artist')->search({
303 name => [ 'Billy Joel', 'Brittany Spears' ],
306 my $rs = $schema->resultset('CD')->search({
307 artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
310 The usual operators ( =, !=, IN, NOT IN, etc) are supported.
312 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
313 The following will B<not> work:
315 my $rs = $schema->resultset('CD')->search({
316 artist_id => $inside_rs->get_column('id')->as_query,
319 =head3 Correlated subqueries
321 my $cdrs = $schema->resultset('CD');
322 my $rs = $cdrs->search({
324 '=' => $cdrs->search(
325 { artistid => { '=' => \'me.artistid' } },
327 )->get_column('year')->max_rs->as_query,
331 That creates the following SQL:
333 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
336 SELECT MAX(inner.year)
338 WHERE artistid = me.artistid
341 =head2 Predefined searches
343 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
344 and define often used searches as methods:
346 package My::DBIC::ResultSet::CD;
349 use base 'DBIx::Class::ResultSet';
351 sub search_cds_ordered {
354 return $self->search(
356 { order_by => 'name DESC' },
362 To use your resultset, first tell DBIx::Class to create an instance of it
363 for you, in your My::DBIC::Schema::CD class:
365 # class definition as normal
366 __PACKAGE__->load_components(qw/ Core /);
367 __PACKAGE__->table('cd');
369 # tell DBIC to use the custom ResultSet class
370 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
372 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
374 Then call your new method in your code:
376 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
378 =head2 Using SQL functions on the left hand side of a comparison
380 Using SQL functions on the left hand side of a comparison is generally
381 not a good idea since it requires a scan of the entire table. However,
382 it can be accomplished with C<DBIx::Class> when necessary.
384 If you do not have quoting on, simply include the function in your search
385 specification as you would any column:
387 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
389 With quoting on, or for a more portable solution, use the C<where>
392 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
396 (When the bind args ordering bug is fixed, this technique will be better
397 and can replace the one above.)
399 With quoting on, or for a more portable solution, use the C<where> and
403 where => \'YEAR(date_of_birth) = ?',
409 =head1 JOINS AND PREFETCHING
411 =head2 Using joins and prefetch
413 You can use the C<join> attribute to allow searching on, or sorting your
414 results by, one or more columns in a related table. To return all CDs matching
415 a particular artist name:
417 my $rs = $schema->resultset('CD')->search(
419 'artist.name' => 'Bob Marley'
422 join => 'artist', # join the artist table
427 # SELECT cd.* FROM cd
428 # JOIN artist ON cd.artist = artist.id
429 # WHERE artist.name = 'Bob Marley'
431 If required, you can now sort on any column in the related tables by including
432 it in your C<order_by> attribute:
434 my $rs = $schema->resultset('CD')->search(
436 'artist.name' => 'Bob Marley'
440 order_by => [qw/ artist.name /]
445 # SELECT cd.* FROM cd
446 # JOIN artist ON cd.artist = artist.id
447 # WHERE artist.name = 'Bob Marley'
448 # ORDER BY artist.name
450 Note that the C<join> attribute should only be used when you need to search or
451 sort using columns in a related table. Joining related tables when you only
452 need columns from the main table will make performance worse!
454 Now let's say you want to display a list of CDs, each with the name of the
455 artist. The following will work fine:
457 while (my $cd = $rs->next) {
458 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
461 There is a problem however. We have searched both the C<cd> and C<artist> tables
462 in our main query, but we have only returned data from the C<cd> table. To get
463 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
466 SELECT artist.* FROM artist WHERE artist.id = ?
468 A statement like the one above will run for each and every CD returned by our
469 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
472 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
473 This allows you to fetch results from related tables in advance:
475 my $rs = $schema->resultset('CD')->search(
477 'artist.name' => 'Bob Marley'
481 order_by => [qw/ artist.name /],
482 prefetch => 'artist' # return artist data too!
486 # Equivalent SQL (note SELECT from both "cd" and "artist"):
487 # SELECT cd.*, artist.* FROM cd
488 # JOIN artist ON cd.artist = artist.id
489 # WHERE artist.name = 'Bob Marley'
490 # ORDER BY artist.name
492 The code to print the CD list remains the same:
494 while (my $cd = $rs->next) {
495 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
498 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
499 so no additional SQL statements are executed. You now have a much more
502 Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
503 C<has_many> relationships.
505 Also note that C<prefetch> should only be used when you know you will
506 definitely use data from a related table. Pre-fetching related tables when you
507 only need columns from the main table will make performance worse!
509 =head2 Multiple joins
511 In the examples above, the C<join> attribute was a scalar. If you
512 pass an array reference instead, you can join to multiple tables. In
513 this example, we want to limit the search further, using
516 # Relationships defined elsewhere:
517 # CD->belongs_to('artist' => 'Artist');
518 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
519 my $rs = $schema->resultset('CD')->search(
521 'artist.name' => 'Bob Marley'
522 'liner_notes.notes' => { 'like', '%some text%' },
525 join => [qw/ artist liner_notes /],
526 order_by => [qw/ artist.name /],
531 # SELECT cd.*, artist.*, liner_notes.* FROM cd
532 # JOIN artist ON cd.artist = artist.id
533 # JOIN liner_notes ON cd.id = liner_notes.cd
534 # WHERE artist.name = 'Bob Marley'
535 # ORDER BY artist.name
537 =head2 Multi-step joins
539 Sometimes you want to join more than one relationship deep. In this example,
540 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
541 contain a specific string:
543 # Relationships defined elsewhere:
544 # Artist->has_many('cds' => 'CD', 'artist');
545 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
547 my $rs = $schema->resultset('Artist')->search(
549 'liner_notes.notes' => { 'like', '%some text%' },
553 'cds' => 'liner_notes'
559 # SELECT artist.* FROM artist
560 # LEFT JOIN cd ON artist.id = cd.artist
561 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
562 # WHERE liner_notes.notes LIKE '%some text%'
564 Joins can be nested to an arbitrary level. So if we decide later that we
565 want to reduce the number of Artists returned based on who wrote the liner
568 # Relationship defined elsewhere:
569 # LinerNotes->belongs_to('author' => 'Person');
571 my $rs = $schema->resultset('Artist')->search(
573 'liner_notes.notes' => { 'like', '%some text%' },
574 'author.name' => 'A. Writer'
579 'liner_notes' => 'author'
586 # SELECT artist.* FROM artist
587 # LEFT JOIN cd ON artist.id = cd.artist
588 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
589 # LEFT JOIN author ON author.id = liner_notes.author
590 # WHERE liner_notes.notes LIKE '%some text%'
591 # AND author.name = 'A. Writer'
593 =head2 Multi-step and multiple joins
595 With various combinations of array and hash references, you can join
596 tables in any combination you desire. For example, to join Artist to
597 CD and Concert, and join CD to LinerNotes:
599 # Relationships defined elsewhere:
600 # Artist->has_many('concerts' => 'Concert', 'artist');
602 my $rs = $schema->resultset('Artist')->search(
615 # SELECT artist.* FROM artist
616 # LEFT JOIN cd ON artist.id = cd.artist
617 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
618 # LEFT JOIN concert ON artist.id = concert.artist
620 =head2 Multi-step prefetch
622 From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
623 deep using the same syntax as a multi-step join:
625 my $rs = $schema->resultset('Tag')->search(
635 # SELECT tag.*, cd.*, artist.* FROM tag
636 # JOIN cd ON tag.cd = cd.id
637 # JOIN artist ON cd.artist = artist.id
639 Now accessing our C<cd> and C<artist> relationships does not need additional
642 my $tag = $rs->first;
643 print $tag->cd->artist->name;
645 =head1 ROW-LEVEL OPERATIONS
647 =head2 Retrieving a row object's Schema
649 It is possible to get a Schema object from a row object like so:
651 my $schema = $cd->result_source->schema;
652 # use the schema as normal:
653 my $artist_rs = $schema->resultset('Artist');
655 This can be useful when you don't want to pass around a Schema object to every
658 =head2 Getting the value of the primary key for the last database insert
660 AKA getting last_insert_id
662 If you are using PK::Auto (which is a core component as of 0.07), this is
665 my $foo = $rs->create(\%blah);
667 my $id = $foo->id; # foo->my_primary_key_field will also work.
669 If you are not using autoincrementing primary keys, this will probably
670 not work, but then you already know the value of the last primary key anyway.
672 =head2 Stringification
674 Employ the standard stringification technique by using the C<overload>
677 To make an object stringify itself as a single column, use something
678 like this (replace C<foo> with the column/method of your choice):
680 use overload '""' => sub { shift->name}, fallback => 1;
682 For more complex stringification, you can use an anonymous subroutine:
684 use overload '""' => sub { $_[0]->name . ", " .
685 $_[0]->address }, fallback => 1;
687 =head3 Stringification Example
689 Suppose we have two tables: C<Product> and C<Category>. The table
692 Product(id, Description, category)
693 Category(id, Description)
695 C<category> is a foreign key into the Category table.
697 If you have a Product object C<$obj> and write something like
701 things will not work as expected.
703 To obtain, for example, the category description, you should add this
704 method to the class defining the Category table:
706 use overload "" => sub {
709 return $self->Description;
712 =head2 Want to know if find_or_create found or created a row?
714 Just use C<find_or_new> instead, then check C<in_storage>:
716 my $obj = $rs->find_or_new({ blah => 'blarg' });
717 unless ($obj->in_storage) {
719 # do whatever else you wanted if it was a new row
722 =head2 Dynamic Sub-classing DBIx::Class proxy classes
724 AKA multi-class object inflation from one table
726 L<DBIx::Class> classes are proxy classes, therefore some different
727 techniques need to be employed for more than basic subclassing. In
728 this example we have a single user table that carries a boolean bit
729 for admin. We would like like to give the admin users
730 objects(L<DBIx::Class::Row>) the same methods as a regular user but
731 also special admin only methods. It doesn't make sense to create two
732 seperate proxy-class files for this. We would be copying all the user
733 methods into the Admin class. There is a cleaner way to accomplish
736 Overriding the C<inflate_result> method within the User proxy-class
737 gives us the effect we want. This method is called by
738 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
739 grab the object being returned, inspect the values we are looking for,
740 bless it if it's an admin object, and then return it. See the example
747 use base qw/DBIx::Class::Schema/;
749 __PACKAGE__->load_classes(qw/User/);
752 B<Proxy-Class definitions>
754 package DB::Schema::User;
758 use base qw/DBIx::Class/;
760 ### Defined what our admin class is for ensure_class_loaded
761 my $admin_class = __PACKAGE__ . '::Admin';
763 __PACKAGE__->load_components(qw/Core/);
765 __PACKAGE__->table('users');
767 __PACKAGE__->add_columns(qw/user_id email password
768 firstname lastname active
771 __PACKAGE__->set_primary_key('user_id');
775 my $ret = $self->next::method(@_);
776 if( $ret->admin ) {### If this is an admin rebless for extra functions
777 $self->ensure_class_loaded( $admin_class );
778 bless $ret, $admin_class;
784 print "I am a regular user.\n";
789 package DB::Schema::User::Admin;
793 use base qw/DB::Schema::User/;
797 print "I am an admin.\n";
803 print "I am doing admin stuff\n";
813 my $user_data = { email => 'someguy@place.com',
817 my $admin_data = { email => 'someadmin@adminplace.com',
821 my $schema = DB::Schema->connection('dbi:Pg:dbname=test');
823 $schema->resultset('User')->create( $user_data );
824 $schema->resultset('User')->create( $admin_data );
826 ### Now we search for them
827 my $user = $schema->resultset('User')->single( $user_data );
828 my $admin = $schema->resultset('User')->single( $admin_data );
830 print ref $user, "\n";
831 print ref $admin, "\n";
833 print $user->password , "\n"; # pass1
834 print $admin->password , "\n";# pass2; inherited from User
835 print $user->hello , "\n";# I am a regular user.
836 print $admin->hello, "\n";# I am an admin.
838 ### The statement below will NOT print
839 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
840 ### The statement below will print
841 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
843 =head2 Skip row object creation for faster results
845 DBIx::Class is not built for speed, it's built for convenience and
846 ease of use, but sometimes you just need to get the data, and skip the
849 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
851 my $rs = $schema->resultset('CD');
853 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
855 my $hash_ref = $rs->find(1);
859 =head2 Get raw data for blindingly fast results
861 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
862 above is not fast enough for you, you can use a DBIx::Class to return values
863 exactly as they come out of the data base with none of the convenience methods
866 This is used like so:
868 my $cursor = $rs->cursor
869 while (my @vals = $cursor->next) {
870 # use $val[0..n] here
873 You will need to map the array offsets to particular columns (you can
874 use the I<select> attribute of C<search()> to force ordering).
876 =head1 RESULTSET OPERATIONS
878 =head2 Getting Schema from a ResultSet
880 To get the schema object from a result set, do the following:
882 $rs->result_source->schema
884 =head2 Getting Columns Of Data
888 If you want to find the sum of a particular column there are several
889 ways, the obvious one is to use search:
891 my $rs = $schema->resultset('Items')->search(
894 select => [ { sum => 'Cost' } ],
895 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
898 my $tc = $rs->first->get_column('total_cost');
900 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
901 returned when you ask the C<ResultSet> for a column using
904 my $cost = $schema->resultset('Items')->get_column('Cost');
907 With this you can also do:
909 my $minvalue = $cost->min;
910 my $maxvalue = $cost->max;
912 Or just iterate through the values of this column only:
914 while ( my $c = $cost->next ) {
918 foreach my $c ($cost->all) {
922 C<ResultSetColumn> only has a limited number of built-in functions, if
923 you need one that it doesn't have, then you can use the C<func> method
926 my $avg = $cost->func('AVERAGE');
928 This will cause the following SQL statement to be run:
930 SELECT AVERAGE(Cost) FROM Items me
932 Which will of course only work if your database supports this function.
933 See L<DBIx::Class::ResultSetColumn> for more documentation.
935 =head2 Creating a result set from a set of rows
937 Sometimes you have a (set of) row objects that you want to put into a
938 resultset without the need to hit the DB again. You can do that by using the
939 L<set_cache|DBIx::Class::Resultset/set_cache> method:
941 my @uploadable_groups;
942 while (my $group = $groups->next) {
943 if ($group->can_upload($self)) {
944 push @uploadable_groups, $group;
947 my $new_rs = $self->result_source->resultset;
948 $new_rs->set_cache(\@uploadable_groups);
952 =head1 USING RELATIONSHIPS
954 =head2 Create a new row in a related table
956 my $author = $book->create_related('author', { name => 'Fred'});
958 =head2 Search in a related table
960 Only searches for books named 'Titanic' by the author in $author.
962 my $books_rs = $author->search_related('books', { name => 'Titanic' });
964 =head2 Delete data in a related table
966 Deletes only the book named Titanic by the author in $author.
968 $author->delete_related('books', { name => 'Titanic' });
970 =head2 Ordering a relationship result set
972 If you always want a relation to be ordered, you can specify this when you
973 create the relationship.
975 To order C<< $book->pages >> by descending page_number, create the relation
978 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
980 =head2 Filtering a relationship result set
982 If you want to get a filtered result set, you can just add add to $attr as follows:
984 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
986 =head2 Many-to-many relationships
988 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
991 use base 'DBIx::Class';
992 __PACKAGE__->load_components('Core');
993 __PACKAGE__->table('user');
994 __PACKAGE__->add_columns(qw/id name/);
995 __PACKAGE__->set_primary_key('id');
996 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
997 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
999 package My::UserAddress;
1000 use base 'DBIx::Class';
1001 __PACKAGE__->load_components('Core');
1002 __PACKAGE__->table('user_address');
1003 __PACKAGE__->add_columns(qw/user address/);
1004 __PACKAGE__->set_primary_key(qw/user address/);
1005 __PACKAGE__->belongs_to('user' => 'My::User');
1006 __PACKAGE__->belongs_to('address' => 'My::Address');
1008 package My::Address;
1009 use base 'DBIx::Class';
1010 __PACKAGE__->load_components('Core');
1011 __PACKAGE__->table('address');
1012 __PACKAGE__->add_columns(qw/id street town area_code country/);
1013 __PACKAGE__->set_primary_key('id');
1014 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1015 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1017 $rs = $user->addresses(); # get all addresses for a user
1018 $rs = $address->users(); # get all users for an address
1022 As of version 0.04001, there is improved transaction support in
1023 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1024 example of the recommended way to use it:
1026 my $genus = $schema->resultset('Genus')->find(12);
1028 my $coderef2 = sub {
1033 my $coderef1 = sub {
1034 $genus->add_to_species({ name => 'troglodyte' });
1037 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1038 return $genus->species;
1043 $rs = $schema->txn_do($coderef1);
1046 if ($@) { # Transaction failed
1047 die "the sky is falling!" #
1048 if ($@ =~ /Rollback failed/); # Rollback failed
1050 deal_with_failed_transaction();
1053 Nested transactions will work as expected. That is, only the outermost
1054 transaction will actually issue a commit to the $dbh, and a rollback
1055 at any level of any transaction will cause the entire nested
1056 transaction to fail. Support for savepoints and for true nested
1057 transactions (for databases that support them) will hopefully be added
1062 =head2 Creating Schemas From An Existing Database
1064 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1065 L<DBIx::Class::Schema> and associated sources by examining the database.
1067 The recommend way of achieving this is to use the
1068 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1070 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1071 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1073 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1074 source definitions for all the tables found in the C<foo> database.
1076 =head2 Creating DDL SQL
1078 The following functionality requires you to have L<SQL::Translator>
1079 (also known as "SQL Fairy") installed.
1081 To create a set of database-specific .sql files for the above schema:
1083 my $schema = My::Schema->connect($dsn);
1084 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1089 By default this will create schema files in the current directory, for
1090 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1092 To create a new database using the schema:
1094 my $schema = My::Schema->connect($dsn);
1095 $schema->deploy({ add_drop_tables => 1});
1097 To import created .sql files using the mysql client:
1099 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1101 To create C<ALTER TABLE> conversion scripts to update a database to a
1102 newer version of your schema at a later point, first set a new
1103 C<$VERSION> in your Schema file, then:
1105 my $schema = My::Schema->connect($dsn);
1106 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1112 This will produce new database-specific .sql files for the new version
1113 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1114 requires that the files for 0.1 as created above are available in the
1115 given directory to diff against.
1117 =head2 Select from dual
1119 Dummy tables are needed by some databases to allow calling functions
1120 or expressions that aren't based on table content, for examples of how
1121 this applies to various database types, see:
1122 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1124 Note: If you're using Oracles dual table don't B<ever> do anything
1125 other than a select, if you CRUD on your dual table you *will* break
1128 Make a table class as you would for any other table
1130 package MyAppDB::Dual;
1133 use base 'DBIx::Class';
1134 __PACKAGE__->load_components("Core");
1135 __PACKAGE__->table("Dual");
1136 __PACKAGE__->add_columns(
1138 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1141 Once you've loaded your table class select from it using C<select>
1142 and C<as> instead of C<columns>
1144 my $rs = $schema->resultset('Dual')->search(undef,
1145 { select => [ 'sydate' ],
1150 All you have to do now is be careful how you access your resultset, the below
1151 will not work because there is no column called 'now' in the Dual table class
1153 while (my $dual = $rs->next) {
1154 print $dual->now."\n";
1156 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1158 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1159 your Dual class for whatever you wanted to select from dual, but that's just
1160 silly, instead use C<get_column>
1162 while (my $dual = $rs->next) {
1163 print $dual->get_column('now')."\n";
1168 my $cursor = $rs->cursor;
1169 while (my @vals = $cursor->next) {
1170 print $vals[0]."\n";
1173 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1175 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1176 while ( my $dual = $rs->next ) {
1177 print $dual->{now}."\n";
1180 Here are some example C<select> conditions to illustrate the different syntax
1181 you could use for doing stuff like
1182 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1184 # get a sequence value
1185 select => [ 'A_SEQ.nextval' ],
1187 # get create table sql
1188 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1190 # get a random num between 0 and 100
1191 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1194 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1197 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1199 # which day of the week were you born on?
1200 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1202 # select 16 rows from dual
1203 select => [ "'hello'" ],
1205 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1209 =head2 Adding Indexes And Functions To Your SQL
1211 Often you will want indexes on columns on your table to speed up searching. To
1212 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1213 class (refer to the advanced
1214 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1215 to share a hook between multiple sources):
1217 package My::Schema::Artist;
1219 __PACKAGE__->table('artist');
1220 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1222 sub sqlt_deploy_hook {
1223 my ($self, $sqlt_table) = @_;
1225 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1230 Sometimes you might want to change the index depending on the type of the
1231 database for which SQL is being generated:
1233 my ($db_type = $sqlt_table->schema->translator->producer_type)
1234 =~ s/^SQL::Translator::Producer:://;
1236 You can also add hooks to the schema level to stop certain tables being
1243 sub sqlt_deploy_hook {
1244 my ($self, $sqlt_schema) = @_;
1246 $sqlt_schema->drop_table('table_name');
1249 You could also add views, procedures or triggers to the output using
1250 L<SQL::Translator::Schema/add_view>,
1251 L<SQL::Translator::Schema/add_procedure> or
1252 L<SQL::Translator::Schema/add_trigger>.
1255 =head2 Schema versioning
1257 The following example shows simplistically how you might use DBIx::Class to
1258 deploy versioned schemas to your customers. The basic process is as follows:
1264 Create a DBIx::Class schema
1276 Modify schema to change functionality
1280 Deploy update to customers
1284 B<Create a DBIx::Class schema>
1286 This can either be done manually, or generated from an existing database as
1287 described under L</Creating Schemas From An Existing Database>
1291 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1293 B<Deploy to customers>
1295 There are several ways you could deploy your schema. These are probably
1296 beyond the scope of this recipe, but might include:
1302 Require customer to apply manually using their RDBMS.
1306 Package along with your app, making database dump/schema update/tests
1307 all part of your install.
1311 B<Modify the schema to change functionality>
1313 As your application evolves, it may be necessary to modify your schema
1314 to change functionality. Once the changes are made to your schema in
1315 DBIx::Class, export the modified schema and the conversion scripts as
1316 in L</Creating DDL SQL>.
1318 B<Deploy update to customers>
1320 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1321 Schema class. This will add a new table to your database called
1322 C<dbix_class_schema_vesion> which will keep track of which version is installed
1323 and warn if the user trys to run a newer schema version than the
1324 database thinks it has.
1326 Alternatively, you can send the conversion sql scripts to your
1329 =head2 Setting quoting for the generated SQL.
1331 If the database contains column names with spaces and/or reserved words, they
1332 need to be quoted in the SQL queries. This is done using:
1334 __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
1335 __PACKAGE__->storage->sql_maker->name_sep('.');
1337 The first sets the quote characters. Either a pair of matching
1338 brackets, or a C<"> or C<'>:
1340 __PACKAGE__->storage->sql_maker->quote_char('"');
1342 Check the documentation of your database for the correct quote
1343 characters to use. C<name_sep> needs to be set to allow the SQL
1344 generator to put the quotes the correct place.
1346 In most cases you should set these as part of the arguments passed to
1347 L<DBIx::Class::Schema/connect>:
1349 my $schema = My::Schema->connect(
1359 =head2 Setting limit dialect for SQL::Abstract::Limit
1361 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1362 the remote SQL server by looking at the database handle. This is a
1363 common problem when using the DBD::JDBC, since the DBD-driver only
1364 know that in has a Java-driver available, not which JDBC driver the
1365 Java component has loaded. This specifically sets the limit_dialect
1366 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1369 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1371 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1372 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1374 The limit dialect can also be set at connect time by specifying a
1375 C<limit_dialect> key in the final hash as shown above.
1377 =head2 Working with PostgreSQL array types
1379 If your SQL::Abstract version (>= 1.50) supports it, you can assign to
1380 PostgreSQL array values by passing array references in the C<\%columns>
1381 (C<\%vals>) hashref of the L<DBIx::Class::ResultSet/create> and
1382 L<DBIx::Class::Row/update> family of methods:
1384 $resultset->create({
1385 numbers => [1, 2, 3]
1390 numbers => [1, 2, 3]
1397 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1398 methods) you cannot directly use array references (since this is interpreted as
1399 a list of values to be C<OR>ed), but you can use the following syntax to force
1400 passing them as bind values:
1404 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1408 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1409 placeholders and bind values (subqueries)> for more explanation. Note that
1410 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1411 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1412 arrayrefs together with the column name, like this: C<< [column_name => value]
1415 =head1 BOOTSTRAPPING/MIGRATING
1417 =head2 Easy migration from class-based to schema-based setup
1419 You want to start using the schema-based approach to L<DBIx::Class>
1420 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1421 of existing classes that you don't want to move by hand. Try this nifty script
1425 use SQL::Translator;
1427 my $schema = MyDB->schema_instance;
1429 my $translator = SQL::Translator->new(
1430 debug => $debug || 0,
1431 trace => $trace || 0,
1432 no_comments => $no_comments || 0,
1433 show_warnings => $show_warnings || 0,
1434 add_drop_table => $add_drop_table || 0,
1435 validate => $validate || 0,
1437 'DBIx::Schema' => $schema,
1440 'prefix' => 'My::Schema',
1444 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1445 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1447 my $output = $translator->translate(@args) or die
1448 "Error: " . $translator->error;
1452 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1453 namespace, which is currently left as an exercise for the reader.
1455 =head1 OVERLOADING METHODS
1457 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1458 method calls, useful for things like default values and triggers. You have to
1459 use calls to C<next::method> to overload methods. More information on using
1460 L<Class::C3> with L<DBIx::Class> can be found in
1461 L<DBIx::Class::Manual::Component>.
1463 =head2 Setting default values for a row
1465 It's as simple as overriding the C<new> method. Note the use of
1469 my ( $class, $attrs ) = @_;
1471 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1473 my $new = $class->next::method($attrs);
1478 For more information about C<next::method>, look in the L<Class::C3>
1479 documentation. See also L<DBIx::Class::Manual::Component> for more
1480 ways to write your own base classes to do this.
1482 People looking for ways to do "triggers" with DBIx::Class are probably
1483 just looking for this.
1485 =head2 Changing one field whenever another changes
1487 For example, say that you have three columns, C<id>, C<number>, and
1488 C<squared>. You would like to make changes to C<number> and have
1489 C<squared> be automagically set to the value of C<number> squared.
1490 You can accomplish this by overriding C<store_column>:
1493 my ( $self, $name, $value ) = @_;
1494 if ($name eq 'number') {
1495 $self->squared($value * $value);
1497 $self->next::method($name, $value);
1500 Note that the hard work is done by the call to C<next::method>, which
1501 redispatches your call to store_column in the superclass(es).
1503 =head2 Automatically creating related objects
1505 You might have a class C<Artist> which has many C<CD>s. Further, if you
1506 want to create a C<CD> object every time you insert an C<Artist> object.
1507 You can accomplish this by overriding C<insert> on your objects:
1510 my ( $self, @args ) = @_;
1511 $self->next::method(@args);
1512 $self->cds->new({})->fill_from_artist($self)->insert;
1516 where C<fill_from_artist> is a method you specify in C<CD> which sets
1517 values in C<CD> based on the data in the C<Artist> object you pass in.
1519 =head2 Wrapping/overloading a column accessor
1523 Say you have a table "Camera" and want to associate a description
1524 with each camera. For most cameras, you'll be able to generate the description from
1525 the other columns. However, in a few special cases you may want to associate a
1526 custom description with a camera.
1530 In your database schema, define a description field in the "Camera" table that
1531 can contain text and null values.
1533 In DBIC, we'll overload the column accessor to provide a sane default if no
1534 custom description is defined. The accessor will either return or generate the
1535 description, depending on whether the field is null or not.
1537 First, in your "Camera" schema class, define the description field as follows:
1539 __PACKAGE__->add_columns(description => { accessor => '_description' });
1541 Next, we'll define the accessor-wrapper subroutine:
1546 # If there is an update to the column, we'll let the original accessor
1548 return $self->_description(@_) if @_;
1550 # Fetch the column value.
1551 my $description = $self->_description;
1553 # If there's something in the description field, then just return that.
1554 return $description if defined $description && length $descripton;
1556 # Otherwise, generate a description.
1557 return $self->generate_description;
1560 =head1 DEBUGGING AND PROFILING
1562 =head2 DBIx::Class objects with Data::Dumper
1564 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1565 be hard to find the pertinent data in all the data it can generate.
1566 Specifically, if one naively tries to use it like so,
1570 my $cd = $schema->resultset('CD')->find(1);
1573 several pages worth of data from the CD object's schema and result source will
1574 be dumped to the screen. Since usually one is only interested in a few column
1575 values of the object, this is not very helpful.
1577 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1578 it. Simply define a hook that L<Data::Dumper> will call on the object before
1579 dumping it. For example,
1586 result_source => undef,
1594 local $Data::Dumper::Freezer = '_dumper_hook';
1596 my $cd = $schema->resultset('CD')->find(1);
1598 # dumps $cd without its ResultSource
1600 If the structure of your schema is such that there is a common base class for
1601 all your table classes, simply put a method similar to C<_dumper_hook> in the
1602 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1603 will automagically clean up your data before printing it. See
1604 L<Data::Dumper/EXAMPLES> for more information.
1608 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1609 executed as well as notifications of query completion and transaction
1610 begin/commit. If you'd like to profile the SQL you can subclass the
1611 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1614 package My::Profiler;
1617 use base 'DBIx::Class::Storage::Statistics';
1619 use Time::HiRes qw(time);
1628 $self->print("Executing $sql: ".join(', ', @params)."\n");
1637 my $elapsed = sprintf("%0.4f", time() - $start);
1638 $self->print("Execution took $elapsed seconds.\n");
1644 You can then install that class as the debugging object:
1646 __PACKAGE__->storage->debugobj(new My::Profiler());
1647 __PACKAGE__->storage->debug(1);
1649 A more complicated example might involve storing each execution of SQL in an
1657 my $elapsed = time() - $start;
1658 push(@{ $calls{$sql} }, {
1664 You could then create average, high and low execution times for an SQL
1665 statement and dig down to see if certain parameters cause aberrant behavior.
1666 You might want to check out L<DBIx::Class::QueryLog> as well.
1668 =head1 STARTUP SPEED
1670 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1671 as the ORM loads all the relevant classes. This section examines
1672 techniques for reducing the startup delay.
1674 These tips are are listed in order of decreasing effectiveness - so the
1675 first tip, if applicable, should have the greatest effect on your
1678 =head2 Statically Define Your Schema
1681 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1682 classes dynamically based on the database schema then there will be a
1683 significant startup delay.
1685 For production use a statically defined schema (which can be generated
1686 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1687 the database schema once - see
1688 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1689 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1690 details on creating static schemas from a database).
1692 =head2 Move Common Startup into a Base Class
1694 Typically L<DBIx::Class> result classes start off with
1696 use base qw/DBIx::Class/;
1697 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1699 If this preamble is moved into a common base class:-
1703 use base qw/DBIx::Class/;
1704 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1707 and each result class then uses this as a base:-
1709 use base qw/MyDBICbase/;
1711 then the load_components is only performed once, which can result in a
1712 considerable startup speedup for schemas with many classes.
1714 =head2 Explicitly List Schema Result Classes
1716 The schema class will normally contain
1718 __PACKAGE__->load_classes();
1720 to load the result classes. This will use L<Module::Find|Module::Find>
1721 to find and load the appropriate modules. Explicitly defining the
1722 classes you wish to load will remove the overhead of
1723 L<Module::Find|Module::Find> and the related directory operations:-
1725 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1727 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1728 syntax to load the appropriate classes there is not a direct alternative
1729 avoiding L<Module::Find|Module::Find>.