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 return $rs->page(2); # records for page 2
24 You can get a L<Data::Page> object for the resultset (suitable for use
25 in e.g. a template) using the C<pager> method:
29 =head2 Complex WHERE clauses
31 Sometimes you need to formulate a query using specific operators:
33 my @albums = $schema->resultset('Album')->search({
34 artist => { 'like', '%Lamb%' },
35 title => { 'like', '%Fear of Fours%' },
38 This results in something like the following C<WHERE> clause:
40 WHERE artist LIKE ? AND title LIKE ?
42 And the following bind values for the placeholders: C<'%Lamb%'>, C<'%Fear of
45 Other queries might require slightly more complex logic:
47 my @albums = $schema->resultset('Album')->search({
50 artist => { 'like', '%Smashing Pumpkins%' },
51 title => 'Siamese Dream',
53 artist => 'Starchildren',
57 This results in the following C<WHERE> clause:
59 WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
60 OR artist = 'Starchildren'
62 For more information on generating complex queries, see
63 L<SQL::Abstract/WHERE CLAUSES>.
65 =head2 Retrieve one and only one row from a resultset
67 Sometimes you need only the first "top" row of a resultset. While this
68 can be easily done with L<< $rs->first|DBIx::Class::ResultSet/first
69 >>, it is suboptimal, as a full blown cursor for the resultset will be
70 created and then immediately destroyed after fetching the first row
71 object. L<< $rs->single|DBIx::Class::ResultSet/single >> is designed
72 specifically for this case - it will grab the first returned result
73 without even instantiating a cursor.
75 Before replacing all your calls to C<first()> with C<single()> please observe the
82 While single() takes a search condition just like search() does, it does
83 _not_ accept search attributes. However one can always chain a single() to
86 my $top_cd = $cd_rs->search({}, { order_by => 'rating' })->single;
91 Since single() is the engine behind find(), it is designed to fetch a
92 single row per database query. Thus a warning will be issued when the
93 underlying SELECT returns more than one row. Sometimes however this usage
94 is valid: i.e. we have an arbitrary number of cd's but only one of them is
95 at the top of the charts at any given time. If you know what you are doing,
96 you can silence the warning by explicitly limiting the resultset size:
98 my $top_cd = $cd_rs->search ({}, { order_by => 'rating', rows => 1 })->single;
102 =head2 Arbitrary SQL through a custom ResultSource
104 Sometimes you have to run arbitrary SQL because your query is too complex
105 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
106 be optimized for your database in a special way, but you still want to
107 get the results as a L<DBIx::Class::ResultSet>.
109 This is accomplished by defining a
110 L<ResultSource::View|DBIx::Class::ResultSource::View> for your query,
111 almost like you would define a regular ResultSource.
113 package My::Schema::Result::UserFriendsComplex;
116 use base qw/DBIx::Class::Core/;
118 __PACKAGE__->table_class('DBIx::Class::ResultSource::View');
120 # For the time being this is necessary even for virtual views
121 __PACKAGE__->table($view_name);
124 # ->add_columns, etc.
127 # do not attempt to deploy() this view
128 __PACKAGE__->result_source_instance->is_virtual(1);
130 __PACKAGE__->result_source_instance->view_definition(q[
131 SELECT u.* FROM user u
132 INNER JOIN user_friends f ON u.id = f.user_id
133 WHERE f.friend_user_id = ?
135 SELECT u.* FROM user u
136 INNER JOIN user_friends f ON u.id = f.friend_user_id
140 Next, you can execute your complex query using bind parameters like this:
142 my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {},
144 bind => [ 12345, 12345 ]
148 ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
149 that you cannot modify the rows it contains, e.g. cannot call L</update>,
150 L</delete>, ... on it).
152 Note that you cannot have bind parameters unless is_virtual is set to true.
158 If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
159 method for custom SQL execution, you are highly encouraged to update your code
160 to use a virtual view as above. If you do not want to change your code, and just
161 want to suppress the deprecation warning when you call
162 L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
163 C<deploy> will exclude this "table":
165 sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
169 =head2 Using specific columns
171 When you only want specific columns from a table, you can use
172 C<columns> to specify which ones you need. This is useful to avoid
173 loading columns with large amounts of data that you aren't about to
176 my $rs = $schema->resultset('Artist')->search(
179 columns => [qw/ name /]
184 # SELECT artist.name FROM artist
186 This is a shortcut for C<select> and C<as>, see below. C<columns>
187 cannot be used together with C<select> and C<as>.
189 =head2 Using database functions or stored procedures
191 The combination of C<select> and C<as> can be used to return the result of a
192 database function or stored procedure as a column value. You use C<select> to
193 specify the source for your column value (e.g. a column name, function, or
194 stored procedure name). You then use C<as> to set the column name you will use
195 to access the returned value:
197 my $rs = $schema->resultset('Artist')->search(
200 select => [ 'name', { LENGTH => 'name' } ],
201 as => [qw/ name name_length /],
206 # SELECT name name, LENGTH( name )
209 Note that the C<as> attribute B<has absolutely nothing to do> with the SQL
210 syntax C< SELECT foo AS bar > (see the documentation in
211 L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
212 generated SQL via the C<-as> field attribute as follows:
214 my $rs = $schema->resultset('Artist')->search(
219 '+select' => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ],
220 '+as' => [qw/num_cds/],
221 order_by => { -desc => 'amount_of_cds' },
226 # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds
227 # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
228 # GROUP BY me.artistid, me.name, me.rank, me.charfield
229 # ORDER BY amount_of_cds DESC
232 If your alias exists as a column in your base class (i.e. it was added with
233 L<add_columns|DBIx::Class::ResultSource/add_columns>), you just access it as
234 normal. Our C<Artist> class has a C<name> column, so we just use the C<name>
237 my $artist = $rs->first();
238 my $name = $artist->name();
240 If on the other hand the alias does not correspond to an existing column, you
241 have to fetch the value using the C<get_column> accessor:
243 my $name_length = $artist->get_column('name_length');
245 If you don't like using C<get_column>, you can always create an accessor for
246 any of your aliases using either of these:
248 # Define accessor manually:
249 sub name_length { shift->get_column('name_length'); }
251 # Or use DBIx::Class::AccessorGroup:
252 __PACKAGE__->mk_group_accessors('column' => 'name_length');
254 See also L</Using SQL functions on the left hand side of a comparison>.
256 =head2 SELECT DISTINCT with multiple columns
258 my $rs = $schema->resultset('Artist')->search(
261 columns => [ qw/artist_id name rank/ ],
266 my $rs = $schema->resultset('Artist')->search(
269 columns => [ qw/artist_id name rank/ ],
270 group_by => [ qw/artist_id name rank/ ],
275 # SELECT me.artist_id, me.name, me.rank
277 # GROUP BY artist_id, name, rank
279 =head2 SELECT COUNT(DISTINCT colname)
281 my $rs = $schema->resultset('Artist')->search(
284 columns => [ qw/name/ ],
289 my $rs = $schema->resultset('Artist')->search(
292 columns => [ qw/name/ ],
293 group_by => [ qw/name/ ],
297 my $count = $rs->count;
300 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) me:
302 =head2 Grouping results
304 L<DBIx::Class> supports C<GROUP BY> as follows:
306 my $rs = $schema->resultset('Artist')->search(
310 select => [ 'name', { count => 'cds.id' } ],
311 as => [qw/ name cd_count /],
312 group_by => [qw/ name /]
317 # SELECT name, COUNT( cd.id ) FROM artist
318 # LEFT JOIN cd ON artist.id = cd.artist
321 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
322 are in any way unsure about the use of the attributes above (C< join
323 >, C< select >, C< as > and C< group_by >).
327 You can write subqueries relatively easily in DBIC.
329 my $inside_rs = $schema->resultset('Artist')->search({
330 name => [ 'Billy Joel', 'Brittany Spears' ],
333 my $rs = $schema->resultset('CD')->search({
334 artist_id => { -in => $inside_rs->get_column('id')->as_query },
337 The usual operators ( '=', '!=', -in, -not_in, etc.) are supported.
339 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
340 The following will B<not> work:
342 my $rs = $schema->resultset('CD')->search({
343 artist_id => $inside_rs->get_column('id')->as_query, # does NOT work
348 Subqueries are supported in the where clause (first hashref), and in the
349 from, select, and +select attributes.
351 =head3 Correlated subqueries
353 my $cdrs = $schema->resultset('CD');
354 my $rs = $cdrs->search({
356 '=' => $cdrs->search(
357 { artist_id => { -ident => 'me.artist_id' } },
358 { alias => 'sub_query' }
359 )->get_column('year')->max_rs->as_query,
363 That creates the following SQL:
365 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
368 SELECT MAX(sub_query.year)
370 WHERE artist_id = me.artist_id
373 =head2 Predefined searches
375 You can define frequently used searches as methods by subclassing
376 L<DBIx::Class::ResultSet>:
378 package My::DBIC::ResultSet::CD;
381 use base 'DBIx::Class::ResultSet';
383 sub search_cds_ordered {
386 return $self->search(
388 { order_by => 'name DESC' },
394 If you're using L<DBIx::Class::Schema/load_namespaces>, simply place the file
395 into the C<ResultSet> directory next to your C<Result> directory, and it will
396 be automatically loaded.
398 If however you are still using L<DBIx::Class::Schema/load_classes>, first tell
399 DBIx::Class to create an instance of the ResultSet class for you, in your
400 My::DBIC::Schema::CD class:
402 # class definition as normal
403 use base 'DBIx::Class::Core';
404 __PACKAGE__->table('cd');
406 # tell DBIC to use the custom ResultSet class
407 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
409 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
411 Then call your new method in your code:
413 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
415 =head2 Using SQL functions on the left hand side of a comparison
417 Using SQL functions on the left hand side of a comparison is generally not a
418 good idea since it requires a scan of the entire table. (Unless your RDBMS
419 supports indexes on expressions - including return values of functions - and
420 you create an index on the return value of the function in question.) However,
421 it can be accomplished with C<DBIx::Class> when necessary by resorting to
425 \[ 'YEAR(date_of_birth) = ?', 1979 ]
429 # SELECT * FROM employee WHERE YEAR(date_of_birth) = ?
431 To include the function as part of a larger search, use the '-and' keyword
432 to collect the search conditions:
434 $rs->search({ -and => [
436 \[ 'YEAR(date_of_birth) = ?', 1979 ]
440 # SELECT * FROM employee WHERE name = ? AND YEAR(date_of_birth) = ?
442 Note: the syntax for specifying the bind value's datatype and value is
443 explained in L<DBIx::Class::ResultSet/DBIC BIND VALUES>.
445 See also L<SQL::Abstract/Literal SQL with placeholders and bind values
448 =head2 Software Limits
450 When your RDBMS does not have a working SQL limit mechanism (e.g. Sybase ASE)
451 and L<GenericSubQ|SQL::Abstract::Limit/GenericSubQ> is either too slow or does
452 not work at all, you can try the
453 L<software_limit|DBIx::Class::ResultSet/software_limit>
454 L<DBIx::Class::ResultSet> attribute, which skips over records to simulate limits
459 my $paged_rs = $rs->search({}, {
462 order_by => [ 'me.last_name' ],
466 You can set it as a default for your schema by placing the following in your
469 __PACKAGE__->default_resultset_attributes({ software_limit => 1 });
471 B<WARNING:> If you are dealing with large resultsets and your L<DBI> or
472 ODBC/ADO driver does not have proper cursor support (i.e. it loads the whole
473 resultset into memory) then this feature will be extremely slow and use huge
474 amounts of memory at best, and may cause your process to run out of memory and
475 cause instability on your server at worst, beware!
477 =head1 JOINS AND PREFETCHING
479 =head2 Using joins and prefetch
481 You can use the C<join> attribute to allow searching on, or sorting your
482 results by, one or more columns in a related table.
484 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
486 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
488 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
490 my $rs = $schema->resultset('CD')->search(
492 'artists.name' => 'Bob Marley'
495 join => 'artists', # join the artist table
500 # SELECT cd.* FROM cd
501 # JOIN artist ON cd.artist = artist.id
502 # WHERE artist.name = 'Bob Marley'
504 In that example both the join, and the condition use the relationship name rather than the table name
505 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
507 If required, you can now sort on any column in the related tables by including
508 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
510 my $rs = $schema->resultset('CD')->search(
512 'artists.name' => 'Bob Marley'
516 order_by => [qw/ artists.name /]
521 # SELECT cd.* FROM cd
522 # JOIN artist ON cd.artist = artist.id
523 # WHERE artist.name = 'Bob Marley'
524 # ORDER BY artist.name
526 Note that the C<join> attribute should only be used when you need to search or
527 sort using columns in a related table. Joining related tables when you only
528 need columns from the main table will make performance worse!
530 Now let's say you want to display a list of CDs, each with the name of the
531 artist. The following will work fine:
533 while (my $cd = $rs->next) {
534 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
537 There is a problem however. We have searched both the C<cd> and C<artist> tables
538 in our main query, but we have only returned data from the C<cd> table. To get
539 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
542 SELECT artist.* FROM artist WHERE artist.id = ?
544 A statement like the one above will run for each and every CD returned by our
545 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
548 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
549 This allows you to fetch results from related tables in advance:
551 my $rs = $schema->resultset('CD')->search(
553 'artists.name' => 'Bob Marley'
557 order_by => [qw/ artists.name /],
558 prefetch => 'artists' # return artist data too!
562 # Equivalent SQL (note SELECT from both "cd" and "artist"):
563 # SELECT cd.*, artist.* FROM cd
564 # JOIN artist ON cd.artist = artist.id
565 # WHERE artist.name = 'Bob Marley'
566 # ORDER BY artist.name
568 The code to print the CD list remains the same:
570 while (my $cd = $rs->next) {
571 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
574 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
575 so no additional SQL statements are executed. You now have a much more
578 Also note that C<prefetch> should only be used when you know you will
579 definitely use data from a related table. Pre-fetching related tables when you
580 only need columns from the main table will make performance worse!
582 =head2 Multiple joins
584 In the examples above, the C<join> attribute was a scalar. If you
585 pass an array reference instead, you can join to multiple tables. In
586 this example, we want to limit the search further, using
589 # Relationships defined elsewhere:
590 # CD->belongs_to('artist' => 'Artist');
591 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
592 my $rs = $schema->resultset('CD')->search(
594 'artist.name' => 'Bob Marley'
595 'liner_notes.notes' => { 'like', '%some text%' },
598 join => [qw/ artist liner_notes /],
599 order_by => [qw/ artist.name /],
604 # SELECT cd.*, artist.*, liner_notes.* FROM cd
605 # JOIN artist ON cd.artist = artist.id
606 # JOIN liner_notes ON cd.id = liner_notes.cd
607 # WHERE artist.name = 'Bob Marley' AND liner_notes.notes LIKE '%some text%'
608 # ORDER BY artist.name
610 =head2 Multi-step joins
612 Sometimes you want to join more than one relationship deep. In this example,
613 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
614 contain a specific string:
616 # Relationships defined elsewhere:
617 # Artist->has_many('cds' => 'CD', 'artist');
618 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
620 my $rs = $schema->resultset('Artist')->search(
622 'liner_notes.notes' => { 'like', '%some text%' },
626 'cds' => 'liner_notes'
632 # SELECT artist.* FROM artist
633 # LEFT JOIN cd ON artist.id = cd.artist
634 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
635 # WHERE liner_notes.notes LIKE '%some text%'
637 Joins can be nested to an arbitrary level. So if we decide later that we
638 want to reduce the number of Artists returned based on who wrote the liner
641 # Relationship defined elsewhere:
642 # LinerNotes->belongs_to('author' => 'Person');
644 my $rs = $schema->resultset('Artist')->search(
646 'liner_notes.notes' => { 'like', '%some text%' },
647 'author.name' => 'A. Writer'
652 'liner_notes' => 'author'
659 # SELECT artist.* FROM artist
660 # LEFT JOIN cd ON artist.id = cd.artist
661 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
662 # LEFT JOIN author ON author.id = liner_notes.author
663 # WHERE liner_notes.notes LIKE '%some text%'
664 # AND author.name = 'A. Writer'
666 =head2 Multi-step and multiple joins
668 With various combinations of array and hash references, you can join
669 tables in any combination you desire. For example, to join Artist to
670 CD and Concert, and join CD to LinerNotes:
672 # Relationships defined elsewhere:
673 # Artist->has_many('concerts' => 'Concert', 'artist');
675 my $rs = $schema->resultset('Artist')->search(
688 # SELECT artist.* FROM artist
689 # LEFT JOIN cd ON artist.id = cd.artist
690 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
691 # LEFT JOIN concert ON artist.id = concert.artist
693 =head2 Multi-step prefetch
695 C<prefetch> can be nested more than one relationship
696 deep using the same syntax as a multi-step join:
698 my $rs = $schema->resultset('Tag')->search(
708 # SELECT tag.*, cd.*, artist.* FROM tag
709 # JOIN cd ON tag.cd = cd.id
710 # JOIN artist ON cd.artist = artist.id
712 Now accessing our C<cd> and C<artist> relationships does not need additional
715 my $tag = $rs->first;
716 print $tag->cd->artist->name;
718 =head1 ROW-LEVEL OPERATIONS
720 =head2 Retrieving a result object's Schema
722 It is possible to get a Schema object from a result object like so:
724 my $schema = $cd->result_source->schema;
725 # use the schema as normal:
726 my $artist_rs = $schema->resultset('Artist');
728 This can be useful when you don't want to pass around a Schema object to every
731 =head2 Getting the value of the primary key for the last database insert
733 AKA getting last_insert_id
735 Thanks to the core component PK::Auto, this is straightforward:
737 my $foo = $rs->create(\%blah);
739 my $id = $foo->id; # foo->my_primary_key_field will also work.
741 If you are not using autoincrementing primary keys, this will probably
742 not work, but then you already know the value of the last primary key anyway.
744 =head2 Stringification
746 Employ the standard stringification technique by using the L<overload>
749 To make an object stringify itself as a single column, use something
750 like this (replace C<name> with the column/method of your choice):
752 use overload '""' => sub { shift->name}, fallback => 1;
754 For more complex stringification, you can use an anonymous subroutine:
756 use overload '""' => sub { $_[0]->name . ", " .
757 $_[0]->address }, fallback => 1;
759 =head3 Stringification Example
761 Suppose we have two tables: C<Product> and C<Category>. The table
764 Product(id, Description, category)
765 Category(id, Description)
767 C<category> is a foreign key into the Category table.
769 If you have a Product object C<$obj> and write something like
773 things will not work as expected.
775 To obtain, for example, the category description, you should add this
776 method to the class defining the Category table:
778 use overload "" => sub {
781 return $self->Description;
784 =head2 Want to know if find_or_create found or created a row?
786 Just use C<find_or_new> instead, then check C<in_storage>:
788 my $obj = $rs->find_or_new({ blah => 'blarg' });
789 unless ($obj->in_storage) {
791 # do whatever else you wanted if it was a new row
794 =head2 Static sub-classing DBIx::Class result classes
796 AKA adding additional relationships/methods/etc. to a model for a
797 specific usage of the (shared) model.
801 package My::App::Schema;
803 use base 'DBIx::Class::Schema';
805 # load subclassed classes from My::App::Schema::Result/ResultSet
806 __PACKAGE__->load_namespaces;
808 # load classes from shared model
810 'My::Shared::Model::Result' => [qw/
817 B<Result-Subclass definition>
819 package My::App::Schema::Result::Baz;
823 use base 'My::Shared::Model::Result::Baz';
825 # WARNING: Make sure you call table() again in your subclass,
826 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
827 # and the class name is not correctly registered as a source
828 __PACKAGE__->table('baz');
830 sub additional_method {
831 return "I'm an additional method only needed by this app";
836 =head2 Dynamic Sub-classing DBIx::Class proxy classes
838 AKA multi-class object inflation from one table
840 L<DBIx::Class> classes are proxy classes, therefore some different
841 techniques need to be employed for more than basic subclassing. In
842 this example we have a single user table that carries a boolean bit
843 for admin. We would like to give the admin users
844 objects (L<DBIx::Class::Row>) the same methods as a regular user but
845 also special admin only methods. It doesn't make sense to create two
846 separate proxy-class files for this. We would be copying all the user
847 methods into the Admin class. There is a cleaner way to accomplish
850 Overriding the C<inflate_result> method within the User proxy-class
851 gives us the effect we want. This method is called by
852 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
853 grab the object being returned, inspect the values we are looking for,
854 bless it if it's an admin object, and then return it. See the example
861 use base qw/DBIx::Class::Schema/;
863 __PACKAGE__->load_namespaces;
868 B<Proxy-Class definitions>
870 package My::Schema::Result::User;
874 use base qw/DBIx::Class::Core/;
876 ### Define what our admin class is, for ensure_class_loaded()
877 my $admin_class = __PACKAGE__ . '::Admin';
879 __PACKAGE__->table('users');
881 __PACKAGE__->add_columns(qw/user_id email password
882 firstname lastname active
885 __PACKAGE__->set_primary_key('user_id');
889 my $ret = $self->next::method(@_);
890 if( $ret->admin ) {### If this is an admin, rebless for extra functions
891 $self->ensure_class_loaded( $admin_class );
892 bless $ret, $admin_class;
898 print "I am a regular user.\n";
905 package My::Schema::Result::User::Admin;
909 use base qw/My::Schema::Result::User/;
911 # This line is important
912 __PACKAGE__->table('users');
916 print "I am an admin.\n";
922 print "I am doing admin stuff\n";
934 my $user_data = { email => 'someguy@place.com',
938 my $admin_data = { email => 'someadmin@adminplace.com',
942 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
944 $schema->resultset('User')->create( $user_data );
945 $schema->resultset('User')->create( $admin_data );
947 ### Now we search for them
948 my $user = $schema->resultset('User')->single( $user_data );
949 my $admin = $schema->resultset('User')->single( $admin_data );
951 print ref $user, "\n";
952 print ref $admin, "\n";
954 print $user->password , "\n"; # pass1
955 print $admin->password , "\n";# pass2; inherited from User
956 print $user->hello , "\n";# I am a regular user.
957 print $admin->hello, "\n";# I am an admin.
959 ### The statement below will NOT print
960 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
961 ### The statement below will print
962 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
964 Alternatively you can use L<DBIx::Class::DynamicSubclass> that implements
965 exactly the above functionality.
967 =head2 Skip result object creation for faster results
969 DBIx::Class is not built for speed, it's built for convenience and
970 ease of use, but sometimes you just need to get the data, and skip the
973 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
975 my $rs = $schema->resultset('CD');
977 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
979 my $hash_ref = $rs->find(1);
983 Beware, changing the Result class using
984 L<DBIx::Class::ResultSet/result_class> will replace any existing class
985 completely including any special components loaded using
986 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
988 =head2 Get raw data for blindingly fast results
990 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
991 above is not fast enough for you, you can use a DBIx::Class to return values
992 exactly as they come out of the database with none of the convenience methods
995 This is used like so:
997 my $cursor = $rs->cursor
998 while (my @vals = $cursor->next) {
999 # use $val[0..n] here
1002 You will need to map the array offsets to particular columns (you can
1003 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
1005 =head1 RESULTSET OPERATIONS
1007 =head2 Getting Schema from a ResultSet
1009 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
1011 $rs->result_source->schema
1013 =head2 Getting Columns Of Data
1015 AKA Aggregating Data
1017 If you want to find the sum of a particular column there are several
1018 ways, the obvious one is to use search:
1020 my $rs = $schema->resultset('Items')->search(
1023 select => [ { sum => 'Cost' } ],
1024 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
1027 my $tc = $rs->first->get_column('total_cost');
1029 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
1030 returned when you ask the C<ResultSet> for a column using
1033 my $cost = $schema->resultset('Items')->get_column('Cost');
1034 my $tc = $cost->sum;
1036 With this you can also do:
1038 my $minvalue = $cost->min;
1039 my $maxvalue = $cost->max;
1041 Or just iterate through the values of this column only:
1043 while ( my $c = $cost->next ) {
1047 foreach my $c ($cost->all) {
1051 C<ResultSetColumn> only has a limited number of built-in functions. If
1052 you need one that it doesn't have, then you can use the C<func> method
1055 my $avg = $cost->func('AVERAGE');
1057 This will cause the following SQL statement to be run:
1059 SELECT AVERAGE(Cost) FROM Items me
1061 Which will of course only work if your database supports this function.
1062 See L<DBIx::Class::ResultSetColumn> for more documentation.
1064 =head2 Creating a result set from a set of rows
1066 Sometimes you have a (set of) result objects that you want to put into a
1067 resultset without the need to hit the DB again. You can do that by using the
1068 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1070 my @uploadable_groups;
1071 while (my $group = $groups->next) {
1072 if ($group->can_upload($self)) {
1073 push @uploadable_groups, $group;
1076 my $new_rs = $self->result_source->resultset;
1077 $new_rs->set_cache(\@uploadable_groups);
1081 =head1 USING RELATIONSHIPS
1083 =head2 Create a new row in a related table
1085 my $author = $book->create_related('author', { name => 'Fred'});
1087 =head2 Search in a related table
1089 Only searches for books named 'Titanic' by the author in $author.
1091 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1093 =head2 Delete data in a related table
1095 Deletes only the book named Titanic by the author in $author.
1097 $author->delete_related('books', { name => 'Titanic' });
1099 =head2 Ordering a relationship result set
1101 If you always want a relation to be ordered, you can specify this when you
1102 create the relationship.
1104 To order C<< $book->pages >> by descending page_number, create the relation
1107 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => { -desc => 'page_number'} } );
1109 =head2 Filtering a relationship result set
1111 If you want to get a filtered result set, you can just add to $attr as follows:
1113 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1115 =head2 Many-to-many relationship bridges
1117 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1120 use base 'DBIx::Class::Core';
1121 __PACKAGE__->table('user');
1122 __PACKAGE__->add_columns(qw/id name/);
1123 __PACKAGE__->set_primary_key('id');
1124 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1125 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1127 package My::UserAddress;
1128 use base 'DBIx::Class::Core';
1129 __PACKAGE__->table('user_address');
1130 __PACKAGE__->add_columns(qw/user address/);
1131 __PACKAGE__->set_primary_key(qw/user address/);
1132 __PACKAGE__->belongs_to('user' => 'My::User');
1133 __PACKAGE__->belongs_to('address' => 'My::Address');
1135 package My::Address;
1136 use base 'DBIx::Class::Core';
1137 __PACKAGE__->table('address');
1138 __PACKAGE__->add_columns(qw/id street town area_code country/);
1139 __PACKAGE__->set_primary_key('id');
1140 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1141 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1143 $rs = $user->addresses(); # get all addresses for a user
1144 $rs = $address->users(); # get all users for an address
1146 my $address = $user->add_to_addresses( # returns a My::Address instance,
1147 # NOT a My::UserAddress instance!
1149 country => 'United Kingdom',
1156 =head2 Relationships across DB schemas
1158 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1159 is easy as long as the schemas themselves are all accessible via the same DBI
1160 connection. In most cases, this means that they are on the same database host
1161 as each other and your connecting database user has the proper permissions to them.
1163 To accomplish this one only needs to specify the DB schema name in the table
1164 declaration, like so...
1166 package MyApp::Schema::Result::Artist;
1167 use base qw/DBIx::Class::Core/;
1169 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1171 __PACKAGE__->add_columns(qw/ artist_id name /);
1172 __PACKAGE__->set_primary_key('artist_id');
1173 __PACKAGE__->has_many('cds' => 'MyApp::Schema::Result::Cd');
1177 Whatever string you specify there will be used to build the "FROM" clause in SQL
1180 The big drawback to this is you now have DB schema names hardcoded in your
1181 class files. This becomes especially troublesome if you have multiple instances
1182 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1183 the DB schemas are named based on the environment (e.g. database1_dev).
1185 However, one can dynamically "map" to the proper DB schema by overriding the
1186 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1187 building a renaming facility, like so:
1189 package MyApp::Schema;
1192 extends 'DBIx::Class::Schema';
1194 around connection => sub {
1195 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1197 my $postfix = delete $attr->{schema_name_postfix};
1202 $self->append_db_name($postfix);
1206 sub append_db_name {
1207 my ( $self, $postfix ) = @_;
1211 { $_->name =~ /^\w+\./mx }
1213 { $self->source($_) }
1216 foreach my $source (@sources_with_db) {
1217 my $name = $source->name;
1218 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1220 $source->name($name);
1226 By overriding the L<connection|DBIx::Class::Schama/connection>
1227 method and extracting a custom option from the provided \%attr hashref one can
1228 then simply iterate over all the Schema's ResultSources, renaming them as
1231 To use this facility, simply add or modify the \%attr hashref that is passed to
1232 L<connection|DBIx::Class::Schama/connect>, as follows:
1235 = MyApp::Schema->connect(
1240 schema_name_postfix => '_dev'
1241 # ... Other options as desired ...
1244 Obviously, one could accomplish even more advanced mapping via a hash map or a
1249 =head2 Transactions with txn_do
1251 As of version 0.04001, there is improved transaction support in
1252 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1253 example of the recommended way to use it:
1255 my $genus = $schema->resultset('Genus')->find(12);
1257 my $coderef2 = sub {
1262 my $coderef1 = sub {
1263 $genus->add_to_species({ name => 'troglodyte' });
1266 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1267 return $genus->species;
1273 $rs = $schema->txn_do($coderef1);
1275 # Transaction failed
1276 die "the sky is falling!" #
1277 if ($_ =~ /Rollback failed/); # Rollback failed
1279 deal_with_failed_transaction();
1282 Note: by default C<txn_do> will re-run the coderef one more time if an
1283 error occurs due to client disconnection (e.g. the server is bounced).
1284 You need to make sure that your coderef can be invoked multiple times
1285 without terrible side effects.
1287 Nested transactions will work as expected. That is, only the outermost
1288 transaction will actually issue a commit to the $dbh, and a rollback
1289 at any level of any transaction will cause the entire nested
1290 transaction to fail.
1292 =head2 Nested transactions and auto-savepoints
1294 If savepoints are supported by your RDBMS, it is possible to achieve true
1295 nested transactions with minimal effort. To enable auto-savepoints via nested
1296 transactions, supply the C<< auto_savepoint = 1 >> connection attribute.
1298 Here is an example of true nested transactions. In the example, we start a big
1299 task which will create several rows. Generation of data for each row is a
1300 fragile operation and might fail. If we fail creating something, depending on
1301 the type of failure, we want to abort the whole task, or only skip the failed
1304 my $schema = MySchema->connect("dbi:Pg:dbname=my_db");
1306 # Start a transaction. Every database change from here on will only be
1307 # committed into the database if the try block succeeds.
1311 $schema->txn_do(sub {
1314 my $job = $schema->resultset('Job')->create({ name=> 'big job' });
1315 # SQL: INSERT INTO job ( name) VALUES ( 'big job' );
1319 # Start a nested transaction, which in fact sets a savepoint.
1321 $schema->txn_do(sub {
1322 # SQL: SAVEPOINT savepoint_0;
1324 my $thing = $schema->resultset('Thing')->create({ job=>$job->id });
1325 # SQL: INSERT INTO thing ( job) VALUES ( 1 );
1328 # This will generate an error, thus setting $@
1330 $thing->update({force_fail=>'foo'});
1331 # SQL: UPDATE thing SET force_fail = 'foo'
1332 # WHERE ( id = 42 );
1336 # SQL: ROLLBACK TO SAVEPOINT savepoint_0;
1338 # There was an error while creating a $thing. Depending on the error
1339 # we want to abort the whole transaction, or only rollback the
1340 # changes related to the creation of this $thing
1342 # Abort the whole job
1343 if ($_ =~ /horrible_problem/) {
1344 print "something horrible happend, aborting job!";
1345 die $_; # rethrow error
1348 # Ignore this $thing, report the error, and continue with the
1350 print "Cannot create thing: $_";
1352 # There was no error, so save all changes since the last
1355 # SQL: RELEASE SAVEPOINT savepoint_0;
1363 # There was an error while handling the $job. Rollback all changes
1364 # since the transaction started, including the already committed
1365 # ('released') savepoints. There will be neither a new $job nor any
1366 # $thing entry in the database.
1370 print "ERROR: $exception\n";
1373 # There was no error while handling the $job. Commit all changes.
1374 # Only now other connections can see the newly created $job and
1382 In this example it might be hard to see where the rollbacks, releases and
1383 commits are happening, but it works just the same as for plain L<<txn_do>>: If
1384 the C<try>-block around C<txn_do> fails, a rollback is issued. If the C<try>
1385 succeeds, the transaction is committed (or the savepoint released).
1387 While you can get more fine-grained control using C<svp_begin>, C<svp_release>
1388 and C<svp_rollback>, it is strongly recommended to use C<txn_do> with coderefs.
1390 =head2 Simple Transactions with DBIx::Class::Storage::TxnScopeGuard
1392 An easy way to use transactions is with
1393 L<DBIx::Class::Storage::TxnScopeGuard>. See L</Automatically creating
1394 related objects> for an example.
1396 Note that unlike txn_do, TxnScopeGuard will only make sure the connection is
1397 alive when issuing the C<BEGIN> statement. It will not (and really can not)
1398 retry if the server goes away mid-operations, unlike C<txn_do>.
1402 =head2 Creating Schemas From An Existing Database
1404 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1405 L<DBIx::Class::Schema> and associated sources by examining the database.
1407 The recommend way of achieving this is to use the L<dbicdump> utility or the
1408 L<Catalyst> helper, as described in
1409 L<Manual::Intro|DBIx::Class::Manual::Intro/Using DBIx::Class::Schema::Loader>.
1411 Alternatively, use the
1412 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1414 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1415 -e 'make_schema_at("My::Schema", \
1416 { db_schema => 'myschema', components => ["InflateColumn::DateTime"] }, \
1417 [ "dbi:Pg:dbname=foo", "username", "password" ])'
1419 This will create a tree of files rooted at C<./lib/My/Schema/> containing source
1420 definitions for all the tables found in the C<myschema> schema in the C<foo>
1423 =head2 Creating DDL SQL
1425 The following functionality requires you to have L<SQL::Translator>
1426 (also known as "SQL Fairy") installed.
1428 To create a set of database-specific .sql files for the above schema:
1430 my $schema = My::Schema->connect($dsn);
1431 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1436 By default this will create schema files in the current directory, for
1437 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1439 To create a new database using the schema:
1441 my $schema = My::Schema->connect($dsn);
1442 $schema->deploy({ add_drop_table => 1});
1444 To import created .sql files using the mysql client:
1446 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1448 To create C<ALTER TABLE> conversion scripts to update a database to a
1449 newer version of your schema at a later point, first set a new
1450 C<$VERSION> in your Schema file, then:
1452 my $schema = My::Schema->connect($dsn);
1453 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1459 This will produce new database-specific .sql files for the new version
1460 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1461 requires that the files for 0.1 as created above are available in the
1462 given directory to diff against.
1464 =head2 Select from dual
1466 Dummy tables are needed by some databases to allow calling functions
1467 or expressions that aren't based on table content, for examples of how
1468 this applies to various database types, see:
1469 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1471 Note: If you're using Oracles dual table don't B<ever> do anything
1472 other than a select, if you CRUD on your dual table you *will* break
1475 Make a table class as you would for any other table
1477 package MyAppDB::Dual;
1480 use base 'DBIx::Class::Core';
1481 __PACKAGE__->table("Dual");
1482 __PACKAGE__->add_columns(
1484 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1487 Once you've loaded your table class select from it using C<select>
1488 and C<as> instead of C<columns>
1490 my $rs = $schema->resultset('Dual')->search(undef,
1491 { select => [ 'sydate' ],
1496 All you have to do now is be careful how you access your resultset, the below
1497 will not work because there is no column called 'now' in the Dual table class
1499 while (my $dual = $rs->next) {
1500 print $dual->now."\n";
1502 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1504 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1505 your Dual class for whatever you wanted to select from dual, but that's just
1506 silly, instead use C<get_column>
1508 while (my $dual = $rs->next) {
1509 print $dual->get_column('now')."\n";
1514 my $cursor = $rs->cursor;
1515 while (my @vals = $cursor->next) {
1516 print $vals[0]."\n";
1519 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1520 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1521 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1522 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1523 L<SQL::Translator> to not create table dual:
1526 add_drop_table => 1,
1527 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1529 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1531 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1533 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1534 while ( my $dual = $rs->next ) {
1535 print $dual->{now}."\n";
1538 Here are some example C<select> conditions to illustrate the different syntax
1539 you could use for doing stuff like
1540 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1542 # get a sequence value
1543 select => [ 'A_SEQ.nextval' ],
1545 # get create table sql
1546 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1548 # get a random num between 0 and 100
1549 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1552 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1555 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1557 # which day of the week were you born on?
1558 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1560 # select 16 rows from dual
1561 select => [ "'hello'" ],
1563 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1567 =head2 Adding Indexes And Functions To Your SQL
1569 Often you will want indexes on columns on your table to speed up searching. To
1570 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1571 class (refer to the advanced
1572 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1573 to share a hook between multiple sources):
1575 package My::Schema::Result::Artist;
1577 __PACKAGE__->table('artist');
1578 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1580 sub sqlt_deploy_hook {
1581 my ($self, $sqlt_table) = @_;
1583 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1588 Sometimes you might want to change the index depending on the type of the
1589 database for which SQL is being generated:
1591 my ($db_type = $sqlt_table->schema->translator->producer_type)
1592 =~ s/^SQL::Translator::Producer:://;
1594 You can also add hooks to the schema level to stop certain tables being
1601 sub sqlt_deploy_hook {
1602 my ($self, $sqlt_schema) = @_;
1604 $sqlt_schema->drop_table('table_name');
1607 You could also add views, procedures or triggers to the output using
1608 L<SQL::Translator::Schema/add_view>,
1609 L<SQL::Translator::Schema/add_procedure> or
1610 L<SQL::Translator::Schema/add_trigger>.
1613 =head2 Schema versioning
1615 The following example shows simplistically how you might use DBIx::Class to
1616 deploy versioned schemas to your customers. The basic process is as follows:
1622 Create a DBIx::Class schema
1634 Modify schema to change functionality
1638 Deploy update to customers
1642 B<Create a DBIx::Class schema>
1644 This can either be done manually, or generated from an existing database as
1645 described under L</Creating Schemas From An Existing Database>
1649 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1651 B<Deploy to customers>
1653 There are several ways you could deploy your schema. These are probably
1654 beyond the scope of this recipe, but might include:
1660 Require customer to apply manually using their RDBMS.
1664 Package along with your app, making database dump/schema update/tests
1665 all part of your install.
1669 B<Modify the schema to change functionality>
1671 As your application evolves, it may be necessary to modify your schema
1672 to change functionality. Once the changes are made to your schema in
1673 DBIx::Class, export the modified schema and the conversion scripts as
1674 in L</Creating DDL SQL>.
1676 B<Deploy update to customers>
1678 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1679 Schema class. This will add a new table to your database called
1680 C<dbix_class_schema_vesion> which will keep track of which version is installed
1681 and warn if the user tries to run a newer schema version than the
1682 database thinks it has.
1684 Alternatively, you can send the conversion SQL scripts to your
1687 =head2 Setting quoting for the generated SQL
1689 If the database contains column names with spaces and/or reserved words, they
1690 need to be quoted in the SQL queries. This is done using:
1692 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1693 $schema->storage->sql_maker->name_sep('.');
1695 The first sets the quote characters. Either a pair of matching
1696 brackets, or a C<"> or C<'>:
1698 $schema->storage->sql_maker->quote_char('"');
1700 Check the documentation of your database for the correct quote
1701 characters to use. C<name_sep> needs to be set to allow the SQL
1702 generator to put the quotes the correct place, and defaults to
1703 C<.> if not supplied.
1705 In most cases you should set these as part of the arguments passed to
1706 L<DBIx::Class::Schema/connect>:
1708 my $schema = My::Schema->connect(
1718 In some cases, quoting will be required for all users of a schema. To enforce
1719 this, you can also overload the C<connection> method for your schema class:
1723 my $rv = $self->next::method( @_ );
1724 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1725 $rv->storage->sql_maker->name_sep('.');
1729 =head2 Working with PostgreSQL array types
1731 You can also assign values to PostgreSQL array columns by passing array
1732 references in the C<\%columns> (C<\%vals>) hashref of the
1733 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1736 $resultset->create({
1737 numbers => [1, 2, 3]
1742 numbers => [1, 2, 3]
1749 In conditions (e.g. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1750 methods) you cannot directly use array references (since this is interpreted as
1751 a list of values to be C<OR>ed), but you can use the following syntax to force
1752 passing them as bind values:
1756 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1760 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1761 placeholders and bind values (subqueries)> for more explanation. Note that
1762 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1763 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1764 arrayrefs together with the column name, like this:
1765 C<< [column_name => value] >>.
1767 =head2 Formatting DateTime objects in queries
1769 To ensure C<WHERE> conditions containing L<DateTime> arguments are properly
1770 formatted to be understood by your RDBMS, you must use the C<DateTime>
1771 formatter returned by L<DBIx::Class::Storage::DBI/datetime_parser> to format
1772 any L<DateTime> objects you pass to L<search|DBIx::Class::ResultSet/search>
1773 conditions. Any L<Storage|DBIx::Class::Storage> object attached to your
1774 L<Schema|DBIx::Class::Schema> provides a correct C<DateTime> formatter, so
1775 all you have to do is:
1777 my $dtf = $schema->storage->datetime_parser;
1778 my $rs = $schema->resultset('users')->search(
1782 $dtf->format_datetime($dt_start),
1783 $dtf->format_datetime($dt_end),
1789 Without doing this the query will contain the simple stringification of the
1790 C<DateTime> object, which almost never matches the RDBMS expectations.
1792 This kludge is necessary only for conditions passed to
1793 L<DBIx::Class::ResultSet/search>, whereas
1794 L<create|DBIx::Class::ResultSet/create>,
1795 L<find|DBIx::Class::ResultSet/find>,
1796 L<DBIx::Class::Row/update> (but not L<DBIx::Class::ResultSet/update>) are all
1797 L<DBIx::Class::InflateColumn>-aware and will do the right thing when supplied
1798 an inflated C<DateTime> object.
1800 =head2 Using Unicode
1802 When using unicode character data there are two alternatives -
1803 either your database supports unicode characters (including setting
1804 the utf8 flag on the returned string), or you need to encode/decode
1805 data appropriately each time a string field is inserted into or
1806 retrieved from the database. It is better to avoid
1807 encoding/decoding data and to use your database's own unicode
1808 capabilities if at all possible.
1810 The L<DBIx::Class::UTF8Columns> component handles storing selected
1811 unicode columns in a database that does not directly support
1812 unicode. If used with a database that does correctly handle unicode
1813 then strange and unexpected data corrupt B<will> occur.
1815 The Catalyst Wiki Unicode page at
1816 L<http://wiki.catalystframework.org/wiki/tutorialsandhowtos/using_unicode>
1817 has additional information on the use of Unicode with Catalyst and
1820 The following databases do correctly handle unicode data:-
1824 MySQL supports unicode, and will correctly flag utf8 data from the
1825 database if the C<mysql_enable_utf8> is set in the connect options.
1827 my $schema = My::Schema->connection('dbi:mysql:dbname=test',
1829 { mysql_enable_utf8 => 1} );
1832 When set, a data retrieved from a textual column type (char,
1833 varchar, etc) will have the UTF-8 flag turned on if necessary. This
1834 enables character semantics on that string. You will also need to
1835 ensure that your database / table / column is configured to use
1836 UTF8. See Chapter 10 of the mysql manual for details.
1838 See L<DBD::mysql> for further details.
1842 Information about Oracle support for unicode can be found in
1843 L<DBD::Oracle/Unicode>.
1847 PostgreSQL supports unicode if the character set is correctly set
1848 at database creation time. Additionally the C<pg_enable_utf8>
1849 should be set to ensure unicode data is correctly marked.
1851 my $schema = My::Schema->connection('dbi:Pg:dbname=test',
1853 { pg_enable_utf8 => 1} );
1855 Further information can be found in L<DBD::Pg>.
1859 SQLite version 3 and above natively use unicode internally. To
1860 correctly mark unicode strings taken from the database, the
1861 C<sqlite_unicode> flag should be set at connect time (in versions
1862 of L<DBD::SQLite> prior to 1.27 this attribute was named
1865 my $schema = My::Schema->connection('dbi:SQLite:/tmp/test.db',
1867 { sqlite_unicode => 1} );
1869 =head1 BOOTSTRAPPING/MIGRATING
1871 =head2 Easy migration from class-based to schema-based setup
1873 You want to start using the schema-based approach to L<DBIx::Class>
1874 (see L<DBIx::Class::Manual::Intro/Setting it up manually>), but have an
1875 established class-based setup with lots of existing classes that you don't
1876 want to move by hand. Try this nifty script instead:
1879 use SQL::Translator;
1881 my $schema = MyDB->schema_instance;
1883 my $translator = SQL::Translator->new(
1884 debug => $debug || 0,
1885 trace => $trace || 0,
1886 no_comments => $no_comments || 0,
1887 show_warnings => $show_warnings || 0,
1888 add_drop_table => $add_drop_table || 0,
1889 validate => $validate || 0,
1891 'DBIx::Schema' => $schema,
1894 'prefix' => 'My::Schema',
1898 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1899 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1901 my $output = $translator->translate(@args) or die
1902 "Error: " . $translator->error;
1906 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1907 namespace, which is currently left as an exercise for the reader.
1909 =head1 OVERLOADING METHODS
1911 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1912 method calls, useful for things like default values and triggers. You have to
1913 use calls to C<next::method> to overload methods. More information on using
1914 L<Class::C3> with L<DBIx::Class> can be found in
1915 L<DBIx::Class::Manual::Component>.
1917 =head2 Setting default values for a row
1919 It's as simple as overriding the C<new> method. Note the use of
1923 my ( $class, $attrs ) = @_;
1925 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1927 my $new = $class->next::method($attrs);
1932 For more information about C<next::method>, look in the L<Class::C3>
1933 documentation. See also L<DBIx::Class::Manual::Component> for more
1934 ways to write your own base classes to do this.
1936 People looking for ways to do "triggers" with DBIx::Class are probably
1937 just looking for this.
1939 =head2 Changing one field whenever another changes
1941 For example, say that you have three columns, C<id>, C<number>, and
1942 C<squared>. You would like to make changes to C<number> and have
1943 C<squared> be automagically set to the value of C<number> squared.
1944 You can accomplish this by wrapping the C<number> accessor with the C<around>
1945 method modifier, available through either L<Class::Method::Modifiers>,
1946 L<Moose|Moose::Manual::MethodModifiers> or L<Moose-like|Moo> modules):
1948 around number => sub {
1949 my ($orig, $self) = (shift, shift);
1953 $self->squared( $value * $value );
1959 Note that the hard work is done by the call to C<< $self->$orig >>, which
1960 redispatches your call to store_column in the superclass(es).
1962 Generally, if this is a calculation your database can easily do, try
1963 and avoid storing the calculated value, it is safer to calculate when
1964 needed, than rely on the data being in sync.
1966 =head2 Automatically creating related objects
1968 You might have a class C<Artist> which has many C<CD>s. Further, you
1969 want to create a C<CD> object every time you insert an C<Artist> object.
1970 You can accomplish this by overriding C<insert> on your objects:
1973 my ( $self, @args ) = @_;
1974 $self->next::method(@args);
1975 $self->create_related ('cds', \%initial_cd_data );
1979 If you want to wrap the two inserts in a transaction (for consistency,
1980 an excellent idea), you can use the awesome
1981 L<DBIx::Class::Storage::TxnScopeGuard>:
1984 my ( $self, @args ) = @_;
1986 my $guard = $self->result_source->schema->txn_scope_guard;
1988 $self->next::method(@args);
1989 $self->create_related ('cds', \%initial_cd_data );
1997 =head2 Wrapping/overloading a column accessor
2001 Say you have a table "Camera" and want to associate a description
2002 with each camera. For most cameras, you'll be able to generate the description from
2003 the other columns. However, in a few special cases you may want to associate a
2004 custom description with a camera.
2008 In your database schema, define a description field in the "Camera" table that
2009 can contain text and null values.
2011 In DBIC, we'll overload the column accessor to provide a sane default if no
2012 custom description is defined. The accessor will either return or generate the
2013 description, depending on whether the field is null or not.
2015 First, in your "Camera" schema class, define the description field as follows:
2017 __PACKAGE__->add_columns(description => { accessor => '_description' });
2019 Next, we'll define the accessor-wrapper subroutine:
2024 # If there is an update to the column, we'll let the original accessor
2026 return $self->_description(@_) if @_;
2028 # Fetch the column value.
2029 my $description = $self->_description;
2031 # If there's something in the description field, then just return that.
2032 return $description if defined $description && length $descripton;
2034 # Otherwise, generate a description.
2035 return $self->generate_description;
2038 =head1 DEBUGGING AND PROFILING
2040 =head2 DBIx::Class objects with Data::Dumper
2042 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
2043 be hard to find the pertinent data in all the data it can generate.
2044 Specifically, if one naively tries to use it like so,
2048 my $cd = $schema->resultset('CD')->find(1);
2051 several pages worth of data from the CD object's schema and result source will
2052 be dumped to the screen. Since usually one is only interested in a few column
2053 values of the object, this is not very helpful.
2055 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
2056 it. Simply define a hook that L<Data::Dumper> will call on the object before
2057 dumping it. For example,
2064 result_source => undef,
2072 local $Data::Dumper::Freezer = '_dumper_hook';
2074 my $cd = $schema->resultset('CD')->find(1);
2076 # dumps $cd without its ResultSource
2078 If the structure of your schema is such that there is a common base class for
2079 all your table classes, simply put a method similar to C<_dumper_hook> in the
2080 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
2081 will automagically clean up your data before printing it. See
2082 L<Data::Dumper/EXAMPLES> for more information.
2086 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
2087 executed as well as notifications of query completion and transaction
2088 begin/commit. If you'd like to profile the SQL you can subclass the
2089 L<DBIx::Class::Storage::Statistics> class and write your own profiling
2092 package My::Profiler;
2095 use base 'DBIx::Class::Storage::Statistics';
2097 use Time::HiRes qw(time);
2106 $self->print("Executing $sql: ".join(', ', @params)."\n");
2115 my $elapsed = sprintf("%0.4f", time() - $start);
2116 $self->print("Execution took $elapsed seconds.\n");
2122 You can then install that class as the debugging object:
2124 __PACKAGE__->storage->debugobj(new My::Profiler());
2125 __PACKAGE__->storage->debug(1);
2127 A more complicated example might involve storing each execution of SQL in an
2135 my $elapsed = time() - $start;
2136 push(@{ $calls{$sql} }, {
2142 You could then create average, high and low execution times for an SQL
2143 statement and dig down to see if certain parameters cause aberrant behavior.
2144 You might want to check out L<DBIx::Class::QueryLog> as well.
2146 =head1 IMPROVING PERFORMANCE
2152 Install L<Class::XSAccessor> to speed up L<Class::Accessor::Grouped>.
2156 On Perl 5.8 install L<Class::C3::XS>.
2160 L<prefetch|DBIx::Class::ResultSet/prefetch> relationships, where possible. See
2161 L</Using joins and prefetch>.
2165 Use L<populate|DBIx::Class::ResultSet/populate> in void context to insert data
2166 when you don't need the resulting L<result|DBIx::Class::Manual::ResultClass> objects,
2167 if possible, but see the caveats.
2169 When inserting many rows, for best results, populate a large number of rows at a
2170 time, but not so large that the table is locked for an unacceptably long time.
2172 If using L<create|DBIx::Class::ResultSet/create> instead, use a transaction and
2173 commit every C<X> rows; where C<X> gives you the best performance without
2174 locking the table for too long.
2178 When selecting many rows, if you don't need full-blown L<DBIx::Class::Row>
2179 objects, consider using L<DBIx::Class::ResultClass::HashRefInflator>.
2183 See also L</STARTUP SPEED> and L</MEMORY USAGE> in this document.
2187 =head1 STARTUP SPEED
2189 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
2190 as the ORM loads all the relevant classes. This section examines
2191 techniques for reducing the startup delay.
2193 These tips are listed in order of decreasing effectiveness - so the
2194 first tip, if applicable, should have the greatest effect on your
2197 =head2 Statically Define Your Schema
2200 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
2201 classes dynamically based on the database schema then there will be a
2202 significant startup delay.
2204 For production use a statically defined schema (which can be generated
2205 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
2206 the database schema once - see
2207 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
2208 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
2209 details on creating static schemas from a database).
2211 =head2 Move Common Startup into a Base Class
2213 Typically L<DBIx::Class> result classes start off with
2215 use base qw/DBIx::Class::Core/;
2216 __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
2218 If this preamble is moved into a common base class:-
2222 use base qw/DBIx::Class::Core/;
2223 __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
2226 and each result class then uses this as a base:-
2228 use base qw/MyDBICbase/;
2230 then the load_components is only performed once, which can result in a
2231 considerable startup speedup for schemas with many classes.
2233 =head2 Explicitly List Schema Result Classes
2235 The schema class will normally contain
2237 __PACKAGE__->load_classes();
2239 to load the result classes. This will use L<Module::Find|Module::Find>
2240 to find and load the appropriate modules. Explicitly defining the
2241 classes you wish to load will remove the overhead of
2242 L<Module::Find|Module::Find> and the related directory operations:
2244 __PACKAGE__->load_classes(qw/ CD Artist Track /);
2246 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
2247 syntax to load the appropriate classes there is not a direct alternative
2248 avoiding L<Module::Find|Module::Find>.
2252 =head2 Cached statements
2254 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
2255 This is normally a good idea, but if too many statements are cached, the database may use too much
2256 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
2257 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
2259 # print all currently cached prepared statements
2260 print for keys %{$schema->storage->dbh->{CachedKids}};
2261 # get a count of currently cached prepared statements
2262 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
2264 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
2267 my $kids = $schema->storage->dbh->{CachedKids};
2268 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
2270 But what you probably want is to expire unused statements and not those that are used frequently.
2271 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
2275 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
2276 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },