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 # ->table, ->add_columns, etc.
122 # do not attempt to deploy() this view
123 __PACKAGE__->result_source_instance->is_virtual(1);
125 __PACKAGE__->result_source_instance->view_definition(q[
126 SELECT u.* FROM user u
127 INNER JOIN user_friends f ON u.id = f.user_id
128 WHERE f.friend_user_id = ?
130 SELECT u.* FROM user u
131 INNER JOIN user_friends f ON u.id = f.friend_user_id
135 Next, you can execute your complex query using bind parameters like this:
137 my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {},
139 bind => [ 12345, 12345 ]
143 ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
144 that you cannot modify the rows it contains, e.g. cannot call L</update>,
145 L</delete>, ... on it).
147 Note that you cannot have bind parameters unless is_virtual is set to true.
153 If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
154 method for custom SQL execution, you are highly encouraged to update your code
155 to use a virtual view as above. If you do not want to change your code, and just
156 want to suppress the deprecation warning when you call
157 L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
158 C<deploy> will exclude this "table":
160 sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
164 =head2 Using specific columns
166 When you only want specific columns from a table, you can use
167 C<columns> to specify which ones you need. This is useful to avoid
168 loading columns with large amounts of data that you aren't about to
171 my $rs = $schema->resultset('Artist')->search(
174 columns => [qw/ name /]
179 # SELECT artist.name FROM artist
181 This is a shortcut for C<select> and C<as>, see below. C<columns>
182 cannot be used together with C<select> and C<as>.
184 =head2 Using database functions or stored procedures
186 The combination of C<select> and C<as> can be used to return the result of a
187 database function or stored procedure as a column value. You use C<select> to
188 specify the source for your column value (e.g. a column name, function, or
189 stored procedure name). You then use C<as> to set the column name you will use
190 to access the returned value:
192 my $rs = $schema->resultset('Artist')->search(
195 select => [ 'name', { LENGTH => 'name' } ],
196 as => [qw/ name name_length /],
201 # SELECT name name, LENGTH( name )
204 Note that the C<as> attribute B<has absolutely nothing to do> with the SQL
205 syntax C< SELECT foo AS bar > (see the documentation in
206 L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
207 generated SQL via the C<-as> field attribute as follows:
209 my $rs = $schema->resultset('Artist')->search(
214 '+select' => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ],
215 '+as' => [qw/num_cds/],
216 order_by => { -desc => 'amount_of_cds' },
221 # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds
222 # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
223 # GROUP BY me.artistid, me.name, me.rank, me.charfield
224 # ORDER BY amount_of_cds DESC
227 If your alias exists as a column in your base class (i.e. it was added with
228 L<add_columns|DBIx::Class::ResultSource/add_columns>), you just access it as
229 normal. Our C<Artist> class has a C<name> column, so we just use the C<name>
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 See also L</Using SQL functions on the left hand side of a comparison>.
251 =head2 SELECT DISTINCT with multiple columns
253 my $rs = $schema->resultset('Artist')->search(
256 columns => [ qw/artist_id name rank/ ],
261 my $rs = $schema->resultset('Artist')->search(
264 columns => [ qw/artist_id name rank/ ],
265 group_by => [ qw/artist_id name rank/ ],
270 # SELECT me.artist_id, me.name, me.rank
272 # GROUP BY artist_id, name, rank
274 =head2 SELECT COUNT(DISTINCT colname)
276 my $rs = $schema->resultset('Artist')->search(
279 columns => [ qw/name/ ],
284 my $rs = $schema->resultset('Artist')->search(
287 columns => [ qw/name/ ],
288 group_by => [ qw/name/ ],
292 my $count = $rs->count;
295 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) me:
297 =head2 Grouping results
299 L<DBIx::Class> supports C<GROUP BY> as follows:
301 my $rs = $schema->resultset('Artist')->search(
305 select => [ 'name', { count => 'cds.id' } ],
306 as => [qw/ name cd_count /],
307 group_by => [qw/ name /]
312 # SELECT name, COUNT( cd.id ) FROM artist
313 # LEFT JOIN cd ON artist.id = cd.artist
316 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
317 are in any way unsure about the use of the attributes above (C< join
318 >, C< select >, C< as > and C< group_by >).
322 You can write subqueries relatively easily in DBIC.
324 my $inside_rs = $schema->resultset('Artist')->search({
325 name => [ 'Billy Joel', 'Brittany Spears' ],
328 my $rs = $schema->resultset('CD')->search({
329 artist_id => { -in => $inside_rs->get_column('id')->as_query },
332 The usual operators ( '=', '!=', -in, -not_in, etc.) are supported.
334 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
335 The following will B<not> work:
337 my $rs = $schema->resultset('CD')->search({
338 artist_id => $inside_rs->get_column('id')->as_query, # does NOT work
343 Subqueries are supported in the where clause (first hashref), and in the
344 from, select, and +select attributes.
346 =head3 Correlated subqueries
348 my $cdrs = $schema->resultset('CD');
349 my $rs = $cdrs->search({
351 '=' => $cdrs->search(
352 { artist_id => { '=' => { -ident => 'me.artist_id' } } },
354 )->get_column('year')->max_rs->as_query,
358 That creates the following SQL:
360 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
363 SELECT MAX(inner.year)
365 WHERE artist_id = me.artist_id
368 =head2 Predefined searches
370 You can define frequently used searches as methods by subclassing
371 L<DBIx::Class::ResultSet>:
373 package My::DBIC::ResultSet::CD;
376 use base 'DBIx::Class::ResultSet';
378 sub search_cds_ordered {
381 return $self->search(
383 { order_by => 'name DESC' },
389 If you're using L<DBIx::Class::Schema/load_namespaces>, simply place the file
390 into the C<ResultSet> directory next to your C<Result> directory, and it will
391 be automatically loaded.
393 If however you are still using L<DBIx::Class::Schema/load_classes>, first tell
394 DBIx::Class to create an instance of the ResultSet class for you, in your
395 My::DBIC::Schema::CD class:
397 # class definition as normal
398 use base 'DBIx::Class::Core';
399 __PACKAGE__->table('cd');
401 # tell DBIC to use the custom ResultSet class
402 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
404 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
406 Then call your new method in your code:
408 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
410 =head2 Using SQL functions on the left hand side of a comparison
412 Using SQL functions on the left hand side of a comparison is generally not a
413 good idea since it requires a scan of the entire table. (Unless your RDBMS
414 supports indexes on expressions - including return values of functions - and
415 you create an index on the return value of the function in question.) However,
416 it can be accomplished with C<DBIx::Class> when necessary by resorting to
419 $rs->search(\[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ]);
422 # SELECT * FROM employee WHERE YEAR(date_of_birth) = ?
424 $rs->search({ -and => [
426 \[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ],
430 # SELECT * FROM employee WHERE name = ? AND YEAR(date_of_birth) = ?
432 Note: the C<plain_value> string in the C<< [ plain_value => 1979 ] >> part
433 should be either the same as the name of the column (do this if the type of the
434 return value of the function is the same as the type of the column) or in the
435 case of a function it's currently treated as a dummy string (it is a good idea
436 to use C<plain_value> or something similar to convey intent). The value is
437 currently only significant when handling special column types (BLOBs, arrays,
438 etc.), but this may change in the future.
440 See also L<SQL::Abstract/Literal SQL with placeholders and bind values
443 =head2 Software Limits
445 When your RDBMS does not have a working SQL limit mechanism (e.g. Sybase ASE)
446 and L<GenericSubQ|SQL::Abstract::Limit/GenericSubQ> is either too slow or does
447 not work at all, you can try the
448 L<software_limit|DBIx::Class::ResultSet/software_limit>
449 L<DBIx::Class::ResultSet> attribute, which skips over records to simulate limits
454 my $paged_rs = $rs->search({}, {
457 order_by => [ 'me.last_name' ],
461 You can set it as a default for your schema by placing the following in your
464 __PACKAGE__->default_resultset_attributes({ software_limit => 1 });
466 B<WARNING:> If you are dealing with large resultsets and your L<DBI> or
467 ODBC/ADO driver does not have proper cursor support (i.e. it loads the whole
468 resultset into memory) then this feature will be extremely slow and use huge
469 amounts of memory at best, and may cause your process to run out of memory and
470 cause instability on your server at worst, beware!
472 =head1 JOINS AND PREFETCHING
474 =head2 Using joins and prefetch
476 You can use the C<join> attribute to allow searching on, or sorting your
477 results by, one or more columns in a related table.
479 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
481 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
483 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
485 my $rs = $schema->resultset('CD')->search(
487 'artists.name' => 'Bob Marley'
490 join => 'artists', # join the artist table
495 # SELECT cd.* FROM cd
496 # JOIN artist ON cd.artist = artist.id
497 # WHERE artist.name = 'Bob Marley'
499 In that example both the join, and the condition use the relationship name rather than the table name
500 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
502 If required, you can now sort on any column in the related tables by including
503 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
505 my $rs = $schema->resultset('CD')->search(
507 'artists.name' => 'Bob Marley'
511 order_by => [qw/ artists.name /]
516 # SELECT cd.* FROM cd
517 # JOIN artist ON cd.artist = artist.id
518 # WHERE artist.name = 'Bob Marley'
519 # ORDER BY artist.name
521 Note that the C<join> attribute should only be used when you need to search or
522 sort using columns in a related table. Joining related tables when you only
523 need columns from the main table will make performance worse!
525 Now let's say you want to display a list of CDs, each with the name of the
526 artist. The following will work fine:
528 while (my $cd = $rs->next) {
529 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
532 There is a problem however. We have searched both the C<cd> and C<artist> tables
533 in our main query, but we have only returned data from the C<cd> table. To get
534 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
537 SELECT artist.* FROM artist WHERE artist.id = ?
539 A statement like the one above will run for each and every CD returned by our
540 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
543 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
544 This allows you to fetch results from related tables in advance:
546 my $rs = $schema->resultset('CD')->search(
548 'artists.name' => 'Bob Marley'
552 order_by => [qw/ artists.name /],
553 prefetch => 'artists' # return artist data too!
557 # Equivalent SQL (note SELECT from both "cd" and "artist"):
558 # SELECT cd.*, artist.* FROM cd
559 # JOIN artist ON cd.artist = artist.id
560 # WHERE artist.name = 'Bob Marley'
561 # ORDER BY artist.name
563 The code to print the CD list remains the same:
565 while (my $cd = $rs->next) {
566 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
569 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
570 so no additional SQL statements are executed. You now have a much more
573 Also note that C<prefetch> should only be used when you know you will
574 definitely use data from a related table. Pre-fetching related tables when you
575 only need columns from the main table will make performance worse!
577 =head2 Multiple joins
579 In the examples above, the C<join> attribute was a scalar. If you
580 pass an array reference instead, you can join to multiple tables. In
581 this example, we want to limit the search further, using
584 # Relationships defined elsewhere:
585 # CD->belongs_to('artist' => 'Artist');
586 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
587 my $rs = $schema->resultset('CD')->search(
589 'artist.name' => 'Bob Marley'
590 'liner_notes.notes' => { 'like', '%some text%' },
593 join => [qw/ artist liner_notes /],
594 order_by => [qw/ artist.name /],
599 # SELECT cd.*, artist.*, liner_notes.* FROM cd
600 # JOIN artist ON cd.artist = artist.id
601 # JOIN liner_notes ON cd.id = liner_notes.cd
602 # WHERE artist.name = 'Bob Marley'
603 # ORDER BY artist.name
605 =head2 Multi-step joins
607 Sometimes you want to join more than one relationship deep. In this example,
608 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
609 contain a specific string:
611 # Relationships defined elsewhere:
612 # Artist->has_many('cds' => 'CD', 'artist');
613 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
615 my $rs = $schema->resultset('Artist')->search(
617 'liner_notes.notes' => { 'like', '%some text%' },
621 'cds' => 'liner_notes'
627 # SELECT artist.* FROM artist
628 # LEFT JOIN cd ON artist.id = cd.artist
629 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
630 # WHERE liner_notes.notes LIKE '%some text%'
632 Joins can be nested to an arbitrary level. So if we decide later that we
633 want to reduce the number of Artists returned based on who wrote the liner
636 # Relationship defined elsewhere:
637 # LinerNotes->belongs_to('author' => 'Person');
639 my $rs = $schema->resultset('Artist')->search(
641 'liner_notes.notes' => { 'like', '%some text%' },
642 'author.name' => 'A. Writer'
647 'liner_notes' => 'author'
654 # SELECT artist.* FROM artist
655 # LEFT JOIN cd ON artist.id = cd.artist
656 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
657 # LEFT JOIN author ON author.id = liner_notes.author
658 # WHERE liner_notes.notes LIKE '%some text%'
659 # AND author.name = 'A. Writer'
661 =head2 Multi-step and multiple joins
663 With various combinations of array and hash references, you can join
664 tables in any combination you desire. For example, to join Artist to
665 CD and Concert, and join CD to LinerNotes:
667 # Relationships defined elsewhere:
668 # Artist->has_many('concerts' => 'Concert', 'artist');
670 my $rs = $schema->resultset('Artist')->search(
683 # SELECT artist.* FROM artist
684 # LEFT JOIN cd ON artist.id = cd.artist
685 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
686 # LEFT JOIN concert ON artist.id = concert.artist
688 =head2 Multi-step prefetch
690 C<prefetch> can be nested more than one relationship
691 deep using the same syntax as a multi-step join:
693 my $rs = $schema->resultset('Tag')->search(
703 # SELECT tag.*, cd.*, artist.* FROM tag
704 # JOIN cd ON tag.cd = cd.id
705 # JOIN artist ON cd.artist = artist.id
707 Now accessing our C<cd> and C<artist> relationships does not need additional
710 my $tag = $rs->first;
711 print $tag->cd->artist->name;
713 =head1 ROW-LEVEL OPERATIONS
715 =head2 Retrieving a row object's Schema
717 It is possible to get a Schema object from a row object like so:
719 my $schema = $cd->result_source->schema;
720 # use the schema as normal:
721 my $artist_rs = $schema->resultset('Artist');
723 This can be useful when you don't want to pass around a Schema object to every
726 =head2 Getting the value of the primary key for the last database insert
728 AKA getting last_insert_id
730 Thanks to the core component PK::Auto, this is straightforward:
732 my $foo = $rs->create(\%blah);
734 my $id = $foo->id; # foo->my_primary_key_field will also work.
736 If you are not using autoincrementing primary keys, this will probably
737 not work, but then you already know the value of the last primary key anyway.
739 =head2 Stringification
741 Employ the standard stringification technique by using the L<overload>
744 To make an object stringify itself as a single column, use something
745 like this (replace C<name> with the column/method of your choice):
747 use overload '""' => sub { shift->name}, fallback => 1;
749 For more complex stringification, you can use an anonymous subroutine:
751 use overload '""' => sub { $_[0]->name . ", " .
752 $_[0]->address }, fallback => 1;
754 =head3 Stringification Example
756 Suppose we have two tables: C<Product> and C<Category>. The table
759 Product(id, Description, category)
760 Category(id, Description)
762 C<category> is a foreign key into the Category table.
764 If you have a Product object C<$obj> and write something like
768 things will not work as expected.
770 To obtain, for example, the category description, you should add this
771 method to the class defining the Category table:
773 use overload "" => sub {
776 return $self->Description;
779 =head2 Want to know if find_or_create found or created a row?
781 Just use C<find_or_new> instead, then check C<in_storage>:
783 my $obj = $rs->find_or_new({ blah => 'blarg' });
784 unless ($obj->in_storage) {
786 # do whatever else you wanted if it was a new row
789 =head2 Static sub-classing DBIx::Class result classes
791 AKA adding additional relationships/methods/etc. to a model for a
792 specific usage of the (shared) model.
796 package My::App::Schema;
798 use base 'DBIx::Class::Schema';
800 # load subclassed classes from My::App::Schema::Result/ResultSet
801 __PACKAGE__->load_namespaces;
803 # load classes from shared model
805 'My::Shared::Model::Result' => [qw/
812 B<Result-Subclass definition>
814 package My::App::Schema::Result::Baz;
818 use base 'My::Shared::Model::Result::Baz';
820 # WARNING: Make sure you call table() again in your subclass,
821 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
822 # and the class name is not correctly registered as a source
823 __PACKAGE__->table('baz');
825 sub additional_method {
826 return "I'm an additional method only needed by this app";
831 =head2 Dynamic Sub-classing DBIx::Class proxy classes
833 AKA multi-class object inflation from one table
835 L<DBIx::Class> classes are proxy classes, therefore some different
836 techniques need to be employed for more than basic subclassing. In
837 this example we have a single user table that carries a boolean bit
838 for admin. We would like like to give the admin users
839 objects (L<DBIx::Class::Row>) the same methods as a regular user but
840 also special admin only methods. It doesn't make sense to create two
841 separate proxy-class files for this. We would be copying all the user
842 methods into the Admin class. There is a cleaner way to accomplish
845 Overriding the C<inflate_result> method within the User proxy-class
846 gives us the effect we want. This method is called by
847 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
848 grab the object being returned, inspect the values we are looking for,
849 bless it if it's an admin object, and then return it. See the example
856 use base qw/DBIx::Class::Schema/;
858 __PACKAGE__->load_namespaces;
863 B<Proxy-Class definitions>
865 package My::Schema::Result::User;
869 use base qw/DBIx::Class::Core/;
871 ### Define what our admin class is, for ensure_class_loaded()
872 my $admin_class = __PACKAGE__ . '::Admin';
874 __PACKAGE__->table('users');
876 __PACKAGE__->add_columns(qw/user_id email password
877 firstname lastname active
880 __PACKAGE__->set_primary_key('user_id');
884 my $ret = $self->next::method(@_);
885 if( $ret->admin ) {### If this is an admin, rebless for extra functions
886 $self->ensure_class_loaded( $admin_class );
887 bless $ret, $admin_class;
893 print "I am a regular user.\n";
900 package My::Schema::Result::User::Admin;
904 use base qw/My::Schema::Result::User/;
906 # This line is important
907 __PACKAGE__->table('users');
911 print "I am an admin.\n";
917 print "I am doing admin stuff\n";
929 my $user_data = { email => 'someguy@place.com',
933 my $admin_data = { email => 'someadmin@adminplace.com',
937 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
939 $schema->resultset('User')->create( $user_data );
940 $schema->resultset('User')->create( $admin_data );
942 ### Now we search for them
943 my $user = $schema->resultset('User')->single( $user_data );
944 my $admin = $schema->resultset('User')->single( $admin_data );
946 print ref $user, "\n";
947 print ref $admin, "\n";
949 print $user->password , "\n"; # pass1
950 print $admin->password , "\n";# pass2; inherited from User
951 print $user->hello , "\n";# I am a regular user.
952 print $admin->hello, "\n";# I am an admin.
954 ### The statement below will NOT print
955 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
956 ### The statement below will print
957 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
959 Alternatively you can use L<DBIx::Class::DynamicSubclass> that implements
960 exactly the above functionality.
962 =head2 Skip row object creation for faster results
964 DBIx::Class is not built for speed, it's built for convenience and
965 ease of use, but sometimes you just need to get the data, and skip the
968 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
970 my $rs = $schema->resultset('CD');
972 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
974 my $hash_ref = $rs->find(1);
978 Beware, changing the Result class using
979 L<DBIx::Class::ResultSet/result_class> will replace any existing class
980 completely including any special components loaded using
981 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
983 =head2 Get raw data for blindingly fast results
985 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
986 above is not fast enough for you, you can use a DBIx::Class to return values
987 exactly as they come out of the database with none of the convenience methods
990 This is used like so:
992 my $cursor = $rs->cursor
993 while (my @vals = $cursor->next) {
994 # use $val[0..n] here
997 You will need to map the array offsets to particular columns (you can
998 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
1000 =head1 RESULTSET OPERATIONS
1002 =head2 Getting Schema from a ResultSet
1004 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
1006 $rs->result_source->schema
1008 =head2 Getting Columns Of Data
1010 AKA Aggregating Data
1012 If you want to find the sum of a particular column there are several
1013 ways, the obvious one is to use search:
1015 my $rs = $schema->resultset('Items')->search(
1018 select => [ { sum => 'Cost' } ],
1019 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
1022 my $tc = $rs->first->get_column('total_cost');
1024 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
1025 returned when you ask the C<ResultSet> for a column using
1028 my $cost = $schema->resultset('Items')->get_column('Cost');
1029 my $tc = $cost->sum;
1031 With this you can also do:
1033 my $minvalue = $cost->min;
1034 my $maxvalue = $cost->max;
1036 Or just iterate through the values of this column only:
1038 while ( my $c = $cost->next ) {
1042 foreach my $c ($cost->all) {
1046 C<ResultSetColumn> only has a limited number of built-in functions. If
1047 you need one that it doesn't have, then you can use the C<func> method
1050 my $avg = $cost->func('AVERAGE');
1052 This will cause the following SQL statement to be run:
1054 SELECT AVERAGE(Cost) FROM Items me
1056 Which will of course only work if your database supports this function.
1057 See L<DBIx::Class::ResultSetColumn> for more documentation.
1059 =head2 Creating a result set from a set of rows
1061 Sometimes you have a (set of) row objects that you want to put into a
1062 resultset without the need to hit the DB again. You can do that by using the
1063 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1065 my @uploadable_groups;
1066 while (my $group = $groups->next) {
1067 if ($group->can_upload($self)) {
1068 push @uploadable_groups, $group;
1071 my $new_rs = $self->result_source->resultset;
1072 $new_rs->set_cache(\@uploadable_groups);
1076 =head1 USING RELATIONSHIPS
1078 =head2 Create a new row in a related table
1080 my $author = $book->create_related('author', { name => 'Fred'});
1082 =head2 Search in a related table
1084 Only searches for books named 'Titanic' by the author in $author.
1086 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1088 =head2 Delete data in a related table
1090 Deletes only the book named Titanic by the author in $author.
1092 $author->delete_related('books', { name => 'Titanic' });
1094 =head2 Ordering a relationship result set
1096 If you always want a relation to be ordered, you can specify this when you
1097 create the relationship.
1099 To order C<< $book->pages >> by descending page_number, create the relation
1102 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => { -desc => 'page_number'} } );
1104 =head2 Filtering a relationship result set
1106 If you want to get a filtered result set, you can just add add to $attr as follows:
1108 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1110 =head2 Many-to-many relationship bridges
1112 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1115 use base 'DBIx::Class::Core';
1116 __PACKAGE__->table('user');
1117 __PACKAGE__->add_columns(qw/id name/);
1118 __PACKAGE__->set_primary_key('id');
1119 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1120 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1122 package My::UserAddress;
1123 use base 'DBIx::Class::Core';
1124 __PACKAGE__->table('user_address');
1125 __PACKAGE__->add_columns(qw/user address/);
1126 __PACKAGE__->set_primary_key(qw/user address/);
1127 __PACKAGE__->belongs_to('user' => 'My::User');
1128 __PACKAGE__->belongs_to('address' => 'My::Address');
1130 package My::Address;
1131 use base 'DBIx::Class::Core';
1132 __PACKAGE__->table('address');
1133 __PACKAGE__->add_columns(qw/id street town area_code country/);
1134 __PACKAGE__->set_primary_key('id');
1135 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1136 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1138 $rs = $user->addresses(); # get all addresses for a user
1139 $rs = $address->users(); # get all users for an address
1141 my $address = $user->add_to_addresses( # returns a My::Address instance,
1142 # NOT a My::UserAddress instance!
1144 country => 'United Kingdom',
1151 =head2 Relationships across DB schemas
1153 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1154 is easy as long as the schemas themselves are all accessible via the same DBI
1155 connection. In most cases, this means that they are on the same database host
1156 as each other and your connecting database user has the proper permissions to them.
1158 To accomplish this one only needs to specify the DB schema name in the table
1159 declaration, like so...
1161 package MyDatabase::Main::Artist;
1162 use base qw/DBIx::Class::Core/;
1164 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1166 __PACKAGE__->add_columns(qw/ artist_id name /);
1167 __PACKAGE__->set_primary_key('artist_id');
1168 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1172 Whatever string you specify there will be used to build the "FROM" clause in SQL
1175 The big drawback to this is you now have DB schema names hardcoded in your
1176 class files. This becomes especially troublesome if you have multiple instances
1177 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1178 the DB schemas are named based on the environment (e.g. database1_dev).
1180 However, one can dynamically "map" to the proper DB schema by overriding the
1181 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1182 building a renaming facility, like so:
1184 package MyDatabase::Schema;
1187 extends 'DBIx::Class::Schema';
1189 around connection => sub {
1190 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1192 my $postfix = delete $attr->{schema_name_postfix};
1197 $self->append_db_name($postfix);
1201 sub append_db_name {
1202 my ( $self, $postfix ) = @_;
1206 { $_->name =~ /^\w+\./mx }
1208 { $self->source($_) }
1211 foreach my $source (@sources_with_db) {
1212 my $name = $source->name;
1213 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1215 $source->name($name);
1221 By overridding the L<connection|DBIx::Class::Schama/connection>
1222 method and extracting a custom option from the provided \%attr hashref one can
1223 then simply iterate over all the Schema's ResultSources, renaming them as
1226 To use this facility, simply add or modify the \%attr hashref that is passed to
1227 L<connection|DBIx::Class::Schama/connect>, as follows:
1230 = MyDatabase::Schema->connect(
1235 schema_name_postfix => '_dev'
1236 # ... Other options as desired ...
1239 Obviously, one could accomplish even more advanced mapping via a hash map or a
1244 =head2 Transactions with txn_do
1246 As of version 0.04001, there is improved transaction support in
1247 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1248 example of the recommended way to use it:
1250 my $genus = $schema->resultset('Genus')->find(12);
1252 my $coderef2 = sub {
1257 my $coderef1 = sub {
1258 $genus->add_to_species({ name => 'troglodyte' });
1261 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1262 return $genus->species;
1268 $rs = $schema->txn_do($coderef1);
1270 # Transaction failed
1271 die "the sky is falling!" #
1272 if ($_ =~ /Rollback failed/); # Rollback failed
1274 deal_with_failed_transaction();
1277 Note: by default C<txn_do> will re-run the coderef one more time if an
1278 error occurs due to client disconnection (e.g. the server is bounced).
1279 You need to make sure that your coderef can be invoked multiple times
1280 without terrible side effects.
1282 Nested transactions will work as expected. That is, only the outermost
1283 transaction will actually issue a commit to the $dbh, and a rollback
1284 at any level of any transaction will cause the entire nested
1285 transaction to fail.
1287 =head2 Nested transactions and auto-savepoints
1289 If savepoints are supported by your RDBMS, it is possible to achieve true
1290 nested transactions with minimal effort. To enable auto-savepoints via nested
1291 transactions, supply the C<< auto_savepoint = 1 >> connection attribute.
1293 Here is an example of true nested transactions. In the example, we start a big
1294 task which will create several rows. Generation of data for each row is a
1295 fragile operation and might fail. If we fail creating something, depending on
1296 the type of failure, we want to abort the whole task, or only skip the failed
1299 my $schema = MySchema->connect("dbi:Pg:dbname=my_db");
1301 # Start a transaction. Every database change from here on will only be
1302 # committed into the database if the try block succeeds.
1306 $schema->txn_do(sub {
1309 my $job = $schema->resultset('Job')->create({ name=> 'big job' });
1310 # SQL: INSERT INTO job ( name) VALUES ( 'big job' );
1314 # Start a nested transaction, which in fact sets a savepoint.
1316 $schema->txn_do(sub {
1317 # SQL: SAVEPOINT savepoint_0;
1319 my $thing = $schema->resultset('Thing')->create({ job=>$job->id });
1320 # SQL: INSERT INTO thing ( job) VALUES ( 1 );
1323 # This will generate an error, thus setting $@
1325 $thing->update({force_fail=>'foo'});
1326 # SQL: UPDATE thing SET force_fail = 'foo'
1327 # WHERE ( id = 42 );
1331 # SQL: ROLLBACK TO SAVEPOINT savepoint_0;
1333 # There was an error while creating a $thing. Depending on the error
1334 # we want to abort the whole transaction, or only rollback the
1335 # changes related to the creation of this $thing
1337 # Abort the whole job
1338 if ($_ =~ /horrible_problem/) {
1339 print "something horrible happend, aborting job!";
1340 die $_; # rethrow error
1343 # Ignore this $thing, report the error, and continue with the
1345 print "Cannot create thing: $_";
1347 # There was no error, so save all changes since the last
1350 # SQL: RELEASE SAVEPOINT savepoint_0;
1358 # There was an error while handling the $job. Rollback all changes
1359 # since the transaction started, including the already committed
1360 # ('released') savepoints. There will be neither a new $job nor any
1361 # $thing entry in the database.
1365 print "ERROR: $exception\n";
1368 # There was no error while handling the $job. Commit all changes.
1369 # Only now other connections can see the newly created $job and
1377 In this example it might be hard to see where the rollbacks, releases and
1378 commits are happening, but it works just the same as for plain L<<txn_do>>: If
1379 the C<try>-block around C<txn_do> fails, a rollback is issued. If the C<try>
1380 succeeds, the transaction is committed (or the savepoint released).
1382 While you can get more fine-grained control using C<svp_begin>, C<svp_release>
1383 and C<svp_rollback>, it is strongly recommended to use C<txn_do> with coderefs.
1385 =head2 Simple Transactions with DBIx::Class::Storage::TxnScopeGuard
1387 An easy way to use transactions is with
1388 L<DBIx::Class::Storage::TxnScopeGuard>. See L</Automatically creating
1389 related objects> for an example.
1391 Note that unlike txn_do, TxnScopeGuard will only make sure the connection is
1392 alive when issuing the C<BEGIN> statement. It will not (and really can not)
1393 retry if the server goes away mid-operations, unlike C<txn_do>.
1397 =head2 Creating Schemas From An Existing Database
1399 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1400 L<DBIx::Class::Schema> and associated sources by examining the database.
1402 The recommend way of achieving this is to use the L<dbicdump> utility or the
1403 L<Catalyst> helper, as described in
1404 L<Manual::Intro|DBIx::Class::Manual::Intro/Using DBIx::Class::Schema::Loader>.
1406 Alternatively, use the
1407 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1409 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1410 -e 'make_schema_at("My::Schema", \
1411 { db_schema => 'myschema', components => ["InflateColumn::DateTime"] }, \
1412 [ "dbi:Pg:dbname=foo", "username", "password" ])'
1414 This will create a tree of files rooted at C<./lib/My/Schema/> containing source
1415 definitions for all the tables found in the C<myschema> schema in the C<foo>
1418 =head2 Creating DDL SQL
1420 The following functionality requires you to have L<SQL::Translator>
1421 (also known as "SQL Fairy") installed.
1423 To create a set of database-specific .sql files for the above schema:
1425 my $schema = My::Schema->connect($dsn);
1426 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1431 By default this will create schema files in the current directory, for
1432 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1434 To create a new database using the schema:
1436 my $schema = My::Schema->connect($dsn);
1437 $schema->deploy({ add_drop_table => 1});
1439 To import created .sql files using the mysql client:
1441 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1443 To create C<ALTER TABLE> conversion scripts to update a database to a
1444 newer version of your schema at a later point, first set a new
1445 C<$VERSION> in your Schema file, then:
1447 my $schema = My::Schema->connect($dsn);
1448 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1454 This will produce new database-specific .sql files for the new version
1455 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1456 requires that the files for 0.1 as created above are available in the
1457 given directory to diff against.
1459 =head2 Select from dual
1461 Dummy tables are needed by some databases to allow calling functions
1462 or expressions that aren't based on table content, for examples of how
1463 this applies to various database types, see:
1464 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1466 Note: If you're using Oracles dual table don't B<ever> do anything
1467 other than a select, if you CRUD on your dual table you *will* break
1470 Make a table class as you would for any other table
1472 package MyAppDB::Dual;
1475 use base 'DBIx::Class::Core';
1476 __PACKAGE__->table("Dual");
1477 __PACKAGE__->add_columns(
1479 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1482 Once you've loaded your table class select from it using C<select>
1483 and C<as> instead of C<columns>
1485 my $rs = $schema->resultset('Dual')->search(undef,
1486 { select => [ 'sydate' ],
1491 All you have to do now is be careful how you access your resultset, the below
1492 will not work because there is no column called 'now' in the Dual table class
1494 while (my $dual = $rs->next) {
1495 print $dual->now."\n";
1497 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1499 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1500 your Dual class for whatever you wanted to select from dual, but that's just
1501 silly, instead use C<get_column>
1503 while (my $dual = $rs->next) {
1504 print $dual->get_column('now')."\n";
1509 my $cursor = $rs->cursor;
1510 while (my @vals = $cursor->next) {
1511 print $vals[0]."\n";
1514 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1515 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1516 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1517 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1518 L<SQL::Translator> to not create table dual:
1521 add_drop_table => 1,
1522 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1524 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1526 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1528 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1529 while ( my $dual = $rs->next ) {
1530 print $dual->{now}."\n";
1533 Here are some example C<select> conditions to illustrate the different syntax
1534 you could use for doing stuff like
1535 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1537 # get a sequence value
1538 select => [ 'A_SEQ.nextval' ],
1540 # get create table sql
1541 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1543 # get a random num between 0 and 100
1544 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1547 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1550 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1552 # which day of the week were you born on?
1553 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1555 # select 16 rows from dual
1556 select => [ "'hello'" ],
1558 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1562 =head2 Adding Indexes And Functions To Your SQL
1564 Often you will want indexes on columns on your table to speed up searching. To
1565 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1566 class (refer to the advanced
1567 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1568 to share a hook between multiple sources):
1570 package My::Schema::Result::Artist;
1572 __PACKAGE__->table('artist');
1573 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1575 sub sqlt_deploy_hook {
1576 my ($self, $sqlt_table) = @_;
1578 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1583 Sometimes you might want to change the index depending on the type of the
1584 database for which SQL is being generated:
1586 my ($db_type = $sqlt_table->schema->translator->producer_type)
1587 =~ s/^SQL::Translator::Producer:://;
1589 You can also add hooks to the schema level to stop certain tables being
1596 sub sqlt_deploy_hook {
1597 my ($self, $sqlt_schema) = @_;
1599 $sqlt_schema->drop_table('table_name');
1602 You could also add views, procedures or triggers to the output using
1603 L<SQL::Translator::Schema/add_view>,
1604 L<SQL::Translator::Schema/add_procedure> or
1605 L<SQL::Translator::Schema/add_trigger>.
1608 =head2 Schema versioning
1610 The following example shows simplistically how you might use DBIx::Class to
1611 deploy versioned schemas to your customers. The basic process is as follows:
1617 Create a DBIx::Class schema
1629 Modify schema to change functionality
1633 Deploy update to customers
1637 B<Create a DBIx::Class schema>
1639 This can either be done manually, or generated from an existing database as
1640 described under L</Creating Schemas From An Existing Database>
1644 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1646 B<Deploy to customers>
1648 There are several ways you could deploy your schema. These are probably
1649 beyond the scope of this recipe, but might include:
1655 Require customer to apply manually using their RDBMS.
1659 Package along with your app, making database dump/schema update/tests
1660 all part of your install.
1664 B<Modify the schema to change functionality>
1666 As your application evolves, it may be necessary to modify your schema
1667 to change functionality. Once the changes are made to your schema in
1668 DBIx::Class, export the modified schema and the conversion scripts as
1669 in L</Creating DDL SQL>.
1671 B<Deploy update to customers>
1673 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1674 Schema class. This will add a new table to your database called
1675 C<dbix_class_schema_vesion> which will keep track of which version is installed
1676 and warn if the user tries to run a newer schema version than the
1677 database thinks it has.
1679 Alternatively, you can send the conversion SQL scripts to your
1682 =head2 Setting quoting for the generated SQL
1684 If the database contains column names with spaces and/or reserved words, they
1685 need to be quoted in the SQL queries. This is done using:
1687 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1688 $schema->storage->sql_maker->name_sep('.');
1690 The first sets the quote characters. Either a pair of matching
1691 brackets, or a C<"> or C<'>:
1693 $schema->storage->sql_maker->quote_char('"');
1695 Check the documentation of your database for the correct quote
1696 characters to use. C<name_sep> needs to be set to allow the SQL
1697 generator to put the quotes the correct place, and defaults to
1698 C<.> if not supplied.
1700 In most cases you should set these as part of the arguments passed to
1701 L<DBIx::Class::Schema/connect>:
1703 my $schema = My::Schema->connect(
1713 In some cases, quoting will be required for all users of a schema. To enforce
1714 this, you can also overload the C<connection> method for your schema class:
1718 my $rv = $self->next::method( @_ );
1719 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1720 $rv->storage->sql_maker->name_sep('.');
1724 =head2 Working with PostgreSQL array types
1726 You can also assign values to PostgreSQL array columns by passing array
1727 references in the C<\%columns> (C<\%vals>) hashref of the
1728 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1731 $resultset->create({
1732 numbers => [1, 2, 3]
1737 numbers => [1, 2, 3]
1744 In conditions (e.g. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1745 methods) you cannot directly use array references (since this is interpreted as
1746 a list of values to be C<OR>ed), but you can use the following syntax to force
1747 passing them as bind values:
1751 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1755 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1756 placeholders and bind values (subqueries)> for more explanation. Note that
1757 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1758 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1759 arrayrefs together with the column name, like this:
1760 C<< [column_name => value] >>.
1762 =head2 Formatting DateTime objects in queries
1764 To ensure C<WHERE> conditions containing L<DateTime> arguments are properly
1765 formatted to be understood by your RDBMS, you must use the C<DateTime>
1766 formatter returned by L<DBIx::Class::Storage::DBI/datetime_parser> to format
1767 any L<DateTime> objects you pass to L<search|DBIx::Class::ResultSet/search>
1768 conditions. Any L<Storage|DBIx::Class::Storage> object attached to your
1769 L<Schema|DBIx::Class::Schema> provides a correct C<DateTime> formatter, so
1770 all you have to do is:
1772 my $dtf = $schema->storage->datetime_parser;
1773 my $rs = $schema->resultset('users')->search(
1777 $dtf->format_datetime($dt_start),
1778 $dtf->format_datetime($dt_end),
1784 Without doing this the query will contain the simple stringification of the
1785 C<DateTime> object, which almost never matches the RDBMS expectations.
1787 This kludge is necessary only for conditions passed to
1788 L<DBIx::Class::ResultSet/search>, whereas
1789 L<create|DBIx::Class::ResultSet/create>,
1790 L<find|DBIx::Class::ResultSet/find>,
1791 L<DBIx::Class::Row/update> (but not L<DBIx::Class::ResultSet/update>) are all
1792 L<DBIx::Class::InflateColumn>-aware and will do the right thing when supplied
1793 an inflated C<DateTime> object.
1795 =head2 Using Unicode
1797 When using unicode character data there are two alternatives -
1798 either your database supports unicode characters (including setting
1799 the utf8 flag on the returned string), or you need to encode/decode
1800 data appropriately each time a string field is inserted into or
1801 retrieved from the database. It is better to avoid
1802 encoding/decoding data and to use your database's own unicode
1803 capabilities if at all possible.
1805 The L<DBIx::Class::UTF8Columns> component handles storing selected
1806 unicode columns in a database that does not directly support
1807 unicode. If used with a database that does correctly handle unicode
1808 then strange and unexpected data corrupt B<will> occur.
1810 The Catalyst Wiki Unicode page at
1811 L<http://wiki.catalystframework.org/wiki/tutorialsandhowtos/using_unicode>
1812 has additional information on the use of Unicode with Catalyst and
1815 The following databases do correctly handle unicode data:-
1819 MySQL supports unicode, and will correctly flag utf8 data from the
1820 database if the C<mysql_enable_utf8> is set in the connect options.
1822 my $schema = My::Schema->connection('dbi:mysql:dbname=test',
1824 { mysql_enable_utf8 => 1} );
1827 When set, a data retrieved from a textual column type (char,
1828 varchar, etc) will have the UTF-8 flag turned on if necessary. This
1829 enables character semantics on that string. You will also need to
1830 ensure that your database / table / column is configured to use
1831 UTF8. See Chapter 10 of the mysql manual for details.
1833 See L<DBD::mysql> for further details.
1837 Information about Oracle support for unicode can be found in
1838 L<DBD::Oracle/Unicode>.
1842 PostgreSQL supports unicode if the character set is correctly set
1843 at database creation time. Additionally the C<pg_enable_utf8>
1844 should be set to ensure unicode data is correctly marked.
1846 my $schema = My::Schema->connection('dbi:Pg:dbname=test',
1848 { pg_enable_utf8 => 1} );
1850 Further information can be found in L<DBD::Pg>.
1854 SQLite version 3 and above natively use unicode internally. To
1855 correctly mark unicode strings taken from the database, the
1856 C<sqlite_unicode> flag should be set at connect time (in versions
1857 of L<DBD::SQLite> prior to 1.27 this attribute was named
1860 my $schema = My::Schema->connection('dbi:SQLite:/tmp/test.db',
1862 { sqlite_unicode => 1} );
1864 =head1 BOOTSTRAPPING/MIGRATING
1866 =head2 Easy migration from class-based to schema-based setup
1868 You want to start using the schema-based approach to L<DBIx::Class>
1869 (see L<DBIx::Class::Manual::Intro/Setting it up manually>), but have an
1870 established class-based setup with lots of existing classes that you don't
1871 want to move by hand. Try this nifty script instead:
1874 use SQL::Translator;
1876 my $schema = MyDB->schema_instance;
1878 my $translator = SQL::Translator->new(
1879 debug => $debug || 0,
1880 trace => $trace || 0,
1881 no_comments => $no_comments || 0,
1882 show_warnings => $show_warnings || 0,
1883 add_drop_table => $add_drop_table || 0,
1884 validate => $validate || 0,
1886 'DBIx::Schema' => $schema,
1889 'prefix' => 'My::Schema',
1893 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1894 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1896 my $output = $translator->translate(@args) or die
1897 "Error: " . $translator->error;
1901 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1902 namespace, which is currently left as an exercise for the reader.
1904 =head1 OVERLOADING METHODS
1906 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1907 method calls, useful for things like default values and triggers. You have to
1908 use calls to C<next::method> to overload methods. More information on using
1909 L<Class::C3> with L<DBIx::Class> can be found in
1910 L<DBIx::Class::Manual::Component>.
1912 =head2 Setting default values for a row
1914 It's as simple as overriding the C<new> method. Note the use of
1918 my ( $class, $attrs ) = @_;
1920 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1922 my $new = $class->next::method($attrs);
1927 For more information about C<next::method>, look in the L<Class::C3>
1928 documentation. See also L<DBIx::Class::Manual::Component> for more
1929 ways to write your own base classes to do this.
1931 People looking for ways to do "triggers" with DBIx::Class are probably
1932 just looking for this.
1934 =head2 Changing one field whenever another changes
1936 For example, say that you have three columns, C<id>, C<number>, and
1937 C<squared>. You would like to make changes to C<number> and have
1938 C<squared> be automagically set to the value of C<number> squared.
1939 You can accomplish this by wrapping the C<number> accessor with
1940 L<Class::Method::Modifiers>:
1942 around number => sub {
1943 my ($orig, $self) = (shift, shift);
1947 $self->squared( $value * $value );
1953 Note that the hard work is done by the call to C<< $self->$orig >>, which
1954 redispatches your call to store_column in the superclass(es).
1956 Generally, if this is a calculation your database can easily do, try
1957 and avoid storing the calculated value, it is safer to calculate when
1958 needed, than rely on the data being in sync.
1960 =head2 Automatically creating related objects
1962 You might have a class C<Artist> which has many C<CD>s. Further, you
1963 want to create a C<CD> object every time you insert an C<Artist> object.
1964 You can accomplish this by overriding C<insert> on your objects:
1967 my ( $self, @args ) = @_;
1968 $self->next::method(@args);
1969 $self->create_related ('cds', \%initial_cd_data );
1973 If you want to wrap the two inserts in a transaction (for consistency,
1974 an excellent idea), you can use the awesome
1975 L<DBIx::Class::Storage::TxnScopeGuard>:
1978 my ( $self, @args ) = @_;
1980 my $guard = $self->result_source->schema->txn_scope_guard;
1982 $self->next::method(@args);
1983 $self->create_related ('cds', \%initial_cd_data );
1991 =head2 Wrapping/overloading a column accessor
1995 Say you have a table "Camera" and want to associate a description
1996 with each camera. For most cameras, you'll be able to generate the description from
1997 the other columns. However, in a few special cases you may want to associate a
1998 custom description with a camera.
2002 In your database schema, define a description field in the "Camera" table that
2003 can contain text and null values.
2005 In DBIC, we'll overload the column accessor to provide a sane default if no
2006 custom description is defined. The accessor will either return or generate the
2007 description, depending on whether the field is null or not.
2009 First, in your "Camera" schema class, define the description field as follows:
2011 __PACKAGE__->add_columns(description => { accessor => '_description' });
2013 Next, we'll define the accessor-wrapper subroutine:
2018 # If there is an update to the column, we'll let the original accessor
2020 return $self->_description(@_) if @_;
2022 # Fetch the column value.
2023 my $description = $self->_description;
2025 # If there's something in the description field, then just return that.
2026 return $description if defined $description && length $descripton;
2028 # Otherwise, generate a description.
2029 return $self->generate_description;
2032 =head1 DEBUGGING AND PROFILING
2034 =head2 DBIx::Class objects with Data::Dumper
2036 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
2037 be hard to find the pertinent data in all the data it can generate.
2038 Specifically, if one naively tries to use it like so,
2042 my $cd = $schema->resultset('CD')->find(1);
2045 several pages worth of data from the CD object's schema and result source will
2046 be dumped to the screen. Since usually one is only interested in a few column
2047 values of the object, this is not very helpful.
2049 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
2050 it. Simply define a hook that L<Data::Dumper> will call on the object before
2051 dumping it. For example,
2058 result_source => undef,
2066 local $Data::Dumper::Freezer = '_dumper_hook';
2068 my $cd = $schema->resultset('CD')->find(1);
2070 # dumps $cd without its ResultSource
2072 If the structure of your schema is such that there is a common base class for
2073 all your table classes, simply put a method similar to C<_dumper_hook> in the
2074 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
2075 will automagically clean up your data before printing it. See
2076 L<Data::Dumper/EXAMPLES> for more information.
2080 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
2081 executed as well as notifications of query completion and transaction
2082 begin/commit. If you'd like to profile the SQL you can subclass the
2083 L<DBIx::Class::Storage::Statistics> class and write your own profiling
2086 package My::Profiler;
2089 use base 'DBIx::Class::Storage::Statistics';
2091 use Time::HiRes qw(time);
2100 $self->print("Executing $sql: ".join(', ', @params)."\n");
2109 my $elapsed = sprintf("%0.4f", time() - $start);
2110 $self->print("Execution took $elapsed seconds.\n");
2116 You can then install that class as the debugging object:
2118 __PACKAGE__->storage->debugobj(new My::Profiler());
2119 __PACKAGE__->storage->debug(1);
2121 A more complicated example might involve storing each execution of SQL in an
2129 my $elapsed = time() - $start;
2130 push(@{ $calls{$sql} }, {
2136 You could then create average, high and low execution times for an SQL
2137 statement and dig down to see if certain parameters cause aberrant behavior.
2138 You might want to check out L<DBIx::Class::QueryLog> as well.
2140 =head1 IMPROVING PERFORMANCE
2146 Install L<Class::XSAccessor> to speed up L<Class::Accessor::Grouped>.
2150 On Perl 5.8 install L<Class::C3::XS>.
2154 L<prefetch|DBIx::Class::ResultSet/prefetch> relationships, where possible. See
2155 L</Using joins and prefetch>.
2159 Use L<populate|DBIx::Class::ResultSet/populate> in void context to insert data
2160 when you don't need the resulting L<DBIx::Class::Row> objects, if possible, but
2163 When inserting many rows, for best results, populate a large number of rows at a
2164 time, but not so large that the table is locked for an unacceptably long time.
2166 If using L<create|DBIx::Class::ResultSet/create> instead, use a transaction and
2167 commit every C<X> rows; where C<X> gives you the best performance without
2168 locking the table for too long.
2172 When selecting many rows, if you don't need full-blown L<DBIx::Class::Row>
2173 objects, consider using L<DBIx::Class::ResultClass::HashRefInflator>.
2177 See also L</STARTUP SPEED> and L</MEMORY USAGE> in this document.
2181 =head1 STARTUP SPEED
2183 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
2184 as the ORM loads all the relevant classes. This section examines
2185 techniques for reducing the startup delay.
2187 These tips are are listed in order of decreasing effectiveness - so the
2188 first tip, if applicable, should have the greatest effect on your
2191 =head2 Statically Define Your Schema
2194 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
2195 classes dynamically based on the database schema then there will be a
2196 significant startup delay.
2198 For production use a statically defined schema (which can be generated
2199 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
2200 the database schema once - see
2201 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
2202 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
2203 details on creating static schemas from a database).
2205 =head2 Move Common Startup into a Base Class
2207 Typically L<DBIx::Class> result classes start off with
2209 use base qw/DBIx::Class::Core/;
2210 __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
2212 If this preamble is moved into a common base class:-
2216 use base qw/DBIx::Class::Core/;
2217 __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
2220 and each result class then uses this as a base:-
2222 use base qw/MyDBICbase/;
2224 then the load_components is only performed once, which can result in a
2225 considerable startup speedup for schemas with many classes.
2227 =head2 Explicitly List Schema Result Classes
2229 The schema class will normally contain
2231 __PACKAGE__->load_classes();
2233 to load the result classes. This will use L<Module::Find|Module::Find>
2234 to find and load the appropriate modules. Explicitly defining the
2235 classes you wish to load will remove the overhead of
2236 L<Module::Find|Module::Find> and the related directory operations:
2238 __PACKAGE__->load_classes(qw/ CD Artist Track /);
2240 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
2241 syntax to load the appropriate classes there is not a direct alternative
2242 avoiding L<Module::Find|Module::Find>.
2246 =head2 Cached statements
2248 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
2249 This is normally a good idea, but if too many statements are cached, the database may use too much
2250 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
2251 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
2253 # print all currently cached prepared statements
2254 print for keys %{$schema->storage->dbh->{CachedKids}};
2255 # get a count of currently cached prepared statements
2256 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
2258 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
2261 my $kids = $schema->storage->dbh->{CachedKids};
2262 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
2264 But what you probably want is to expire unused statements and not those that are used frequently.
2265 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
2269 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
2270 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },