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
150 L<update|DBIx::Class::ResultSet/update> or
151 L<delete|DBIx::Class::ResultSet/delete> on it).
153 Note that you cannot have bind parameters unless is_virtual is set to true.
159 If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
160 method for custom SQL execution, you are highly encouraged to update your code
161 to use a virtual view as above. If you do not want to change your code, and just
162 want to suppress the deprecation warning when you call
163 L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
164 C<deploy> will exclude this "table":
166 sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
170 =head2 Using specific columns
172 When you only want specific columns from a table, you can use
173 C<columns> to specify which ones you need. This is useful to avoid
174 loading columns with large amounts of data that you aren't about to
177 my $rs = $schema->resultset('Artist')->search(
180 columns => [qw/ name /]
185 # SELECT artist.name FROM artist
187 This is a shortcut for C<select> and C<as>, see below. C<columns>
188 cannot be used together with C<select> and C<as>.
190 =head2 Using database functions or stored procedures
192 The combination of C<select> and C<as> can be used to return the result of a
193 database function or stored procedure as a column value. You use C<select> to
194 specify the source for your column value (e.g. a column name, function, or
195 stored procedure name). You then use C<as> to set the column name you will use
196 to access the returned value:
198 my $rs = $schema->resultset('Artist')->search(
201 select => [ 'name', { LENGTH => 'name' } ],
202 as => [qw/ name name_length /],
207 # SELECT name name, LENGTH( name )
210 Note that the C<as> attribute B<has absolutely nothing to do> with the SQL
211 syntax C< SELECT foo AS bar > (see the documentation in
212 L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
213 generated SQL via the C<-as> field attribute as follows:
215 my $rs = $schema->resultset('Artist')->search(
220 '+select' => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ],
221 '+as' => [qw/num_cds/],
222 order_by => { -desc => 'amount_of_cds' },
227 # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds
228 # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
229 # GROUP BY me.artistid, me.name, me.rank, me.charfield
230 # ORDER BY amount_of_cds DESC
233 If your alias exists as a column in your base class (i.e. it was added with
234 L<add_columns|DBIx::Class::ResultSource/add_columns>), you just access it as
235 normal. Our C<Artist> class has a C<name> column, so we just use the C<name>
238 my $artist = $rs->first();
239 my $name = $artist->name();
241 If on the other hand the alias does not correspond to an existing column, you
242 have to fetch the value using the C<get_column> accessor:
244 my $name_length = $artist->get_column('name_length');
246 If you don't like using C<get_column>, you can always create an accessor for
247 any of your aliases using either of these:
249 # Define accessor manually:
250 sub name_length { shift->get_column('name_length'); }
252 # Or use DBIx::Class::AccessorGroup:
253 __PACKAGE__->mk_group_accessors('column' => 'name_length');
255 See also L</Using SQL functions on the left hand side of a comparison>.
257 =head2 SELECT DISTINCT with multiple columns
259 my $rs = $schema->resultset('Artist')->search(
262 columns => [ qw/artist_id name rank/ ],
267 my $rs = $schema->resultset('Artist')->search(
270 columns => [ qw/artist_id name rank/ ],
271 group_by => [ qw/artist_id name rank/ ],
276 # SELECT me.artist_id, me.name, me.rank
278 # GROUP BY artist_id, name, rank
280 =head2 SELECT COUNT(DISTINCT colname)
282 my $rs = $schema->resultset('Artist')->search(
285 columns => [ qw/name/ ],
290 my $rs = $schema->resultset('Artist')->search(
293 columns => [ qw/name/ ],
294 group_by => [ qw/name/ ],
298 my $count = $rs->count;
301 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) me:
303 =head2 Grouping results
305 L<DBIx::Class> supports C<GROUP BY> as follows:
307 my $rs = $schema->resultset('Artist')->search(
311 select => [ 'name', { count => 'cds.id' } ],
312 as => [qw/ name cd_count /],
313 group_by => [qw/ name /]
318 # SELECT name, COUNT( cd.id ) FROM artist
319 # LEFT JOIN cd ON artist.id = cd.artist
322 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
323 are in any way unsure about the use of the attributes above (C< join
324 >, C< select >, C< as > and C< group_by >).
328 You can write subqueries relatively easily in DBIC.
330 my $inside_rs = $schema->resultset('Artist')->search({
331 name => [ 'Billy Joel', 'Brittany Spears' ],
334 my $rs = $schema->resultset('CD')->search({
335 artist_id => { -in => $inside_rs->get_column('id')->as_query },
338 The usual operators ( '=', '!=', -in, -not_in, etc.) are supported.
340 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
341 The following will B<not> work:
343 my $rs = $schema->resultset('CD')->search({
344 artist_id => $inside_rs->get_column('id')->as_query, # does NOT work
349 Subqueries are supported in the where clause (first hashref), and in the
350 from, select, and +select attributes.
352 =head3 Correlated subqueries
354 my $cdrs = $schema->resultset('CD');
355 my $rs = $cdrs->search({
357 '=' => $cdrs->search(
358 { artist_id => { -ident => 'me.artist_id' } },
359 { alias => 'sub_query' }
360 )->get_column('year')->max_rs->as_query,
364 That creates the following SQL:
366 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
369 SELECT MAX(sub_query.year)
371 WHERE artist_id = me.artist_id
374 =head2 Predefined searches
376 You can define frequently used searches as methods by subclassing
377 L<DBIx::Class::ResultSet>:
379 package My::DBIC::ResultSet::CD;
382 use base 'DBIx::Class::ResultSet';
384 sub search_cds_ordered {
387 return $self->search(
389 { order_by => 'name DESC' },
395 If you're using L<DBIx::Class::Schema/load_namespaces>, simply place the file
396 into the C<ResultSet> directory next to your C<Result> directory, and it will
397 be automatically loaded.
399 If however you are still using L<DBIx::Class::Schema/load_classes>, first tell
400 DBIx::Class to create an instance of the ResultSet class for you, in your
401 My::DBIC::Schema::CD class:
403 # class definition as normal
404 use base 'DBIx::Class::Core';
405 __PACKAGE__->table('cd');
407 # tell DBIC to use the custom ResultSet class
408 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
410 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
412 Then call your new method in your code:
414 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
416 =head2 Using SQL functions on the left hand side of a comparison
418 Using SQL functions on the left hand side of a comparison is generally not a
419 good idea since it requires a scan of the entire table. (Unless your RDBMS
420 supports indexes on expressions - including return values of functions - and
421 you create an index on the return value of the function in question.) However,
422 it can be accomplished with C<DBIx::Class> when necessary by resorting to
426 \[ 'YEAR(date_of_birth) = ?', 1979 ]
430 # SELECT * FROM employee WHERE YEAR(date_of_birth) = ?
432 To include the function as part of a larger search, use the '-and' keyword
433 to collect the search conditions:
435 $rs->search({ -and => [
437 \[ 'YEAR(date_of_birth) = ?', 1979 ]
441 # SELECT * FROM employee WHERE name = ? AND YEAR(date_of_birth) = ?
443 Note: the syntax for specifying the bind value's datatype and value is
444 explained in L<DBIx::Class::ResultSet/DBIC BIND VALUES>.
446 See also L<SQL::Abstract/Literal SQL with placeholders and bind values
449 =head2 Software Limits
451 When your RDBMS does not have a working SQL limit mechanism (e.g. Sybase ASE)
452 and L<GenericSubQ|DBIx::Class::SQLMaker::LimitDialects/GenericSubQ> is either
453 too slow or does not work at all, you can try the
454 L<software_limit|DBIx::Class::ResultSet/software_limit>
455 L<DBIx::Class::ResultSet> attribute, which skips over records to simulate limits
460 my $paged_rs = $rs->search({}, {
463 order_by => [ 'me.last_name' ],
467 You can set it as a default for your schema by placing the following in your
470 __PACKAGE__->default_resultset_attributes({ software_limit => 1 });
472 B<WARNING:> If you are dealing with large resultsets and your L<DBI> or
473 ODBC/ADO driver does not have proper cursor support (i.e. it loads the whole
474 resultset into memory) then this feature will be extremely slow and use huge
475 amounts of memory at best, and may cause your process to run out of memory and
476 cause instability on your server at worst, beware!
478 =head1 JOINS AND PREFETCHING
480 =head2 Using joins and prefetch
482 You can use the C<join> attribute to allow searching on, or sorting your
483 results by, one or more columns in a related table.
485 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
487 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
489 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
491 my $rs = $schema->resultset('CD')->search(
493 'artists.name' => 'Bob Marley'
496 join => 'artists', # join the artist table
501 # SELECT cd.* FROM cd
502 # JOIN artist ON cd.artist = artist.id
503 # WHERE artist.name = 'Bob Marley'
505 In that example both the join, and the condition use the relationship name rather than the table name
506 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
508 If required, you can now sort on any column in the related tables by including
509 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
511 my $rs = $schema->resultset('CD')->search(
513 'artists.name' => 'Bob Marley'
517 order_by => [qw/ artists.name /]
522 # SELECT cd.* FROM cd
523 # JOIN artist ON cd.artist = artist.id
524 # WHERE artist.name = 'Bob Marley'
525 # ORDER BY artist.name
527 Note that the C<join> attribute should only be used when you need to search or
528 sort using columns in a related table. Joining related tables when you only
529 need columns from the main table will make performance worse!
531 Now let's say you want to display a list of CDs, each with the name of the
532 artist. The following will work fine:
534 while (my $cd = $rs->next) {
535 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
538 There is a problem however. We have searched both the C<cd> and C<artist> tables
539 in our main query, but we have only returned data from the C<cd> table. To get
540 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
543 SELECT artist.* FROM artist WHERE artist.id = ?
545 A statement like the one above will run for each and every CD returned by our
546 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
549 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
550 This allows you to fetch results from related tables in advance:
552 my $rs = $schema->resultset('CD')->search(
554 'artists.name' => 'Bob Marley'
558 order_by => [qw/ artists.name /],
559 prefetch => 'artists' # return artist data too!
563 # Equivalent SQL (note SELECT from both "cd" and "artist"):
564 # SELECT cd.*, artist.* FROM cd
565 # JOIN artist ON cd.artist = artist.id
566 # WHERE artist.name = 'Bob Marley'
567 # ORDER BY artist.name
569 The code to print the CD list remains the same:
571 while (my $cd = $rs->next) {
572 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
575 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
576 so no additional SQL statements are executed. You now have a much more
579 Also note that C<prefetch> should only be used when you know you will
580 definitely use data from a related table. Pre-fetching related tables when you
581 only need columns from the main table will make performance worse!
583 =head2 Multiple joins
585 In the examples above, the C<join> attribute was a scalar. If you
586 pass an array reference instead, you can join to multiple tables. In
587 this example, we want to limit the search further, using
590 # Relationships defined elsewhere:
591 # CD->belongs_to('artist' => 'Artist');
592 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
593 my $rs = $schema->resultset('CD')->search(
595 'artist.name' => 'Bob Marley'
596 'liner_notes.notes' => { 'like', '%some text%' },
599 join => [qw/ artist liner_notes /],
600 order_by => [qw/ artist.name /],
605 # SELECT cd.*, artist.*, liner_notes.* FROM cd
606 # JOIN artist ON cd.artist = artist.id
607 # JOIN liner_notes ON cd.id = liner_notes.cd
608 # WHERE artist.name = 'Bob Marley' AND liner_notes.notes LIKE '%some text%'
609 # ORDER BY artist.name
611 =head2 Multi-step joins
613 Sometimes you want to join more than one relationship deep. In this example,
614 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
615 contain a specific string:
617 # Relationships defined elsewhere:
618 # Artist->has_many('cds' => 'CD', 'artist');
619 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
621 my $rs = $schema->resultset('Artist')->search(
623 'liner_notes.notes' => { 'like', '%some text%' },
627 'cds' => 'liner_notes'
633 # SELECT artist.* FROM artist
634 # LEFT JOIN cd ON artist.id = cd.artist
635 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
636 # WHERE liner_notes.notes LIKE '%some text%'
638 Joins can be nested to an arbitrary level. So if we decide later that we
639 want to reduce the number of Artists returned based on who wrote the liner
642 # Relationship defined elsewhere:
643 # LinerNotes->belongs_to('author' => 'Person');
645 my $rs = $schema->resultset('Artist')->search(
647 'liner_notes.notes' => { 'like', '%some text%' },
648 'author.name' => 'A. Writer'
653 'liner_notes' => 'author'
660 # SELECT artist.* FROM artist
661 # LEFT JOIN cd ON artist.id = cd.artist
662 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
663 # LEFT JOIN author ON author.id = liner_notes.author
664 # WHERE liner_notes.notes LIKE '%some text%'
665 # AND author.name = 'A. Writer'
667 =head2 Multi-step and multiple joins
669 With various combinations of array and hash references, you can join
670 tables in any combination you desire. For example, to join Artist to
671 CD and Concert, and join CD to LinerNotes:
673 # Relationships defined elsewhere:
674 # Artist->has_many('concerts' => 'Concert', 'artist');
676 my $rs = $schema->resultset('Artist')->search(
689 # SELECT artist.* FROM artist
690 # LEFT JOIN cd ON artist.id = cd.artist
691 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
692 # LEFT JOIN concert ON artist.id = concert.artist
694 =head2 Multi-step prefetch
696 C<prefetch> can be nested more than one relationship
697 deep using the same syntax as a multi-step join:
699 my $rs = $schema->resultset('Tag')->search(
709 # SELECT tag.*, cd.*, artist.* FROM tag
710 # JOIN cd ON tag.cd = cd.id
711 # JOIN artist ON cd.artist = artist.id
713 Now accessing our C<cd> and C<artist> relationships does not need additional
716 my $tag = $rs->first;
717 print $tag->cd->artist->name;
719 =head1 ROW-LEVEL OPERATIONS
721 =head2 Retrieving a result object's Schema
723 It is possible to get a Schema object from a result object like so:
725 my $schema = $cd->result_source->schema;
726 # use the schema as normal:
727 my $artist_rs = $schema->resultset('Artist');
729 This can be useful when you don't want to pass around a Schema object to every
732 =head2 Getting the value of the primary key for the last database insert
734 AKA getting last_insert_id
736 Thanks to the core component PK::Auto, this is straightforward:
738 my $foo = $rs->create(\%blah);
740 my $id = $foo->id; # foo->my_primary_key_field will also work.
742 If you are not using autoincrementing primary keys, this will probably
743 not work, but then you already know the value of the last primary key anyway.
745 =head2 Stringification
747 Employ the standard stringification technique by using the L<overload>
750 To make an object stringify itself as a single column, use something
751 like this (replace C<name> with the column/method of your choice):
753 use overload '""' => sub { shift->name}, fallback => 1;
755 For more complex stringification, you can use an anonymous subroutine:
757 use overload '""' => sub { $_[0]->name . ", " .
758 $_[0]->address }, fallback => 1;
760 =head3 Stringification Example
762 Suppose we have two tables: C<Product> and C<Category>. The table
765 Product(id, Description, category)
766 Category(id, Description)
768 C<category> is a foreign key into the Category table.
770 If you have a Product object C<$obj> and write something like
774 things will not work as expected.
776 To obtain, for example, the category description, you should add this
777 method to the class defining the Category table:
779 use overload "" => sub {
782 return $self->Description;
785 =head2 Want to know if find_or_create found or created a row?
787 Just use C<find_or_new> instead, then check C<in_storage>:
789 my $obj = $rs->find_or_new({ blah => 'blarg' });
790 unless ($obj->in_storage) {
792 # do whatever else you wanted if it was a new row
795 =head2 Static sub-classing DBIx::Class result classes
797 AKA adding additional relationships/methods/etc. to a model for a
798 specific usage of the (shared) model.
802 package My::App::Schema;
804 use base 'DBIx::Class::Schema';
806 # load subclassed classes from My::App::Schema::Result/ResultSet
807 __PACKAGE__->load_namespaces;
809 # load classes from shared model
811 'My::Shared::Model::Result' => [qw/
818 B<Result-Subclass definition>
820 package My::App::Schema::Result::Baz;
824 use base 'My::Shared::Model::Result::Baz';
826 # WARNING: Make sure you call table() again in your subclass,
827 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
828 # and the class name is not correctly registered as a source
829 __PACKAGE__->table('baz');
831 sub additional_method {
832 return "I'm an additional method only needed by this app";
837 =head2 Dynamic Sub-classing DBIx::Class proxy classes
839 AKA multi-class object inflation from one table
841 L<DBIx::Class> classes are proxy classes, therefore some different
842 techniques need to be employed for more than basic subclassing. In
843 this example we have a single user table that carries a boolean bit
844 for admin. We would like to give the admin users
845 objects (L<DBIx::Class::Row>) the same methods as a regular user but
846 also special admin only methods. It doesn't make sense to create two
847 separate proxy-class files for this. We would be copying all the user
848 methods into the Admin class. There is a cleaner way to accomplish
851 Overriding the C<inflate_result> method within the User proxy-class
852 gives us the effect we want. This method is called by
853 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
854 grab the object being returned, inspect the values we are looking for,
855 bless it if it's an admin object, and then return it. See the example
862 use base qw/DBIx::Class::Schema/;
864 __PACKAGE__->load_namespaces;
869 B<Proxy-Class definitions>
871 package My::Schema::Result::User;
875 use base qw/DBIx::Class::Core/;
877 ### Define what our admin class is, for ensure_class_loaded()
878 my $admin_class = __PACKAGE__ . '::Admin';
880 __PACKAGE__->table('users');
882 __PACKAGE__->add_columns(qw/user_id email password
883 firstname lastname active
886 __PACKAGE__->set_primary_key('user_id');
890 my $ret = $self->next::method(@_);
891 if( $ret->admin ) {### If this is an admin, rebless for extra functions
892 $self->ensure_class_loaded( $admin_class );
893 bless $ret, $admin_class;
899 print "I am a regular user.\n";
906 package My::Schema::Result::User::Admin;
910 use base qw/My::Schema::Result::User/;
912 # This line is important
913 __PACKAGE__->table('users');
917 print "I am an admin.\n";
923 print "I am doing admin stuff\n";
935 my $user_data = { email => 'someguy@place.com',
939 my $admin_data = { email => 'someadmin@adminplace.com',
943 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
945 $schema->resultset('User')->create( $user_data );
946 $schema->resultset('User')->create( $admin_data );
948 ### Now we search for them
949 my $user = $schema->resultset('User')->single( $user_data );
950 my $admin = $schema->resultset('User')->single( $admin_data );
952 print ref $user, "\n";
953 print ref $admin, "\n";
955 print $user->password , "\n"; # pass1
956 print $admin->password , "\n";# pass2; inherited from User
957 print $user->hello , "\n";# I am a regular user.
958 print $admin->hello, "\n";# I am an admin.
960 ### The statement below will NOT print
961 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
962 ### The statement below will print
963 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
965 Alternatively you can use L<DBIx::Class::DynamicSubclass> that implements
966 exactly the above functionality.
968 =head2 Skip result object creation for faster results
970 DBIx::Class is not built for speed, it's built for convenience and
971 ease of use, but sometimes you just need to get the data, and skip the
974 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
976 my $rs = $schema->resultset('CD');
978 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
980 my $hash_ref = $rs->find(1);
984 Beware, changing the Result class using
985 L<DBIx::Class::ResultSet/result_class> will replace any existing class
986 completely including any special components loaded using
987 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
989 =head2 Get raw data for blindingly fast results
991 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
992 above is not fast enough for you, you can use a DBIx::Class to return values
993 exactly as they come out of the database with none of the convenience methods
996 This is used like so:
998 my $cursor = $rs->cursor
999 while (my @vals = $cursor->next) {
1000 # use $val[0..n] here
1003 You will need to map the array offsets to particular columns (you can
1004 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
1006 =head1 RESULTSET OPERATIONS
1008 =head2 Getting Schema from a ResultSet
1010 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
1012 $rs->result_source->schema
1014 =head2 Getting Columns Of Data
1016 AKA Aggregating Data
1018 If you want to find the sum of a particular column there are several
1019 ways, the obvious one is to use search:
1021 my $rs = $schema->resultset('Items')->search(
1024 select => [ { sum => 'Cost' } ],
1025 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
1028 my $tc = $rs->first->get_column('total_cost');
1030 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
1031 returned when you ask the C<ResultSet> for a column using
1034 my $cost = $schema->resultset('Items')->get_column('Cost');
1035 my $tc = $cost->sum;
1037 With this you can also do:
1039 my $minvalue = $cost->min;
1040 my $maxvalue = $cost->max;
1042 Or just iterate through the values of this column only:
1044 while ( my $c = $cost->next ) {
1048 foreach my $c ($cost->all) {
1052 C<ResultSetColumn> only has a limited number of built-in functions. If
1053 you need one that it doesn't have, then you can use the C<func> method
1056 my $avg = $cost->func('AVERAGE');
1058 This will cause the following SQL statement to be run:
1060 SELECT AVERAGE(Cost) FROM Items me
1062 Which will of course only work if your database supports this function.
1063 See L<DBIx::Class::ResultSetColumn> for more documentation.
1065 =head2 Creating a result set from a set of rows
1067 Sometimes you have a (set of) result objects that you want to put into a
1068 resultset without the need to hit the DB again. You can do that by using the
1069 L<set_cache|DBIx::Class::ResultSet/set_cache> method:
1071 my @uploadable_groups;
1072 while (my $group = $groups->next) {
1073 if ($group->can_upload($self)) {
1074 push @uploadable_groups, $group;
1077 my $new_rs = $self->result_source->resultset;
1078 $new_rs->set_cache(\@uploadable_groups);
1082 =head1 USING RELATIONSHIPS
1084 =head2 Create a new row in a related table
1086 my $author = $book->create_related('author', { name => 'Fred'});
1088 =head2 Search in a related table
1090 Only searches for books named 'Titanic' by the author in $author.
1092 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1094 =head2 Delete data in a related table
1096 Deletes only the book named Titanic by the author in $author.
1098 $author->delete_related('books', { name => 'Titanic' });
1100 =head2 Ordering a relationship result set
1102 If you always want a relation to be ordered, you can specify this when you
1103 create the relationship.
1105 To order C<< $book->pages >> by descending page_number, create the relation
1108 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => { -desc => 'page_number'} } );
1110 =head2 Filtering a relationship result set
1112 If you want to get a filtered result set, you can just add to $attr as follows:
1114 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1116 =head2 Many-to-many relationship bridges
1118 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1121 use base 'DBIx::Class::Core';
1122 __PACKAGE__->table('user');
1123 __PACKAGE__->add_columns(qw/id name/);
1124 __PACKAGE__->set_primary_key('id');
1125 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1126 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1128 package My::UserAddress;
1129 use base 'DBIx::Class::Core';
1130 __PACKAGE__->table('user_address');
1131 __PACKAGE__->add_columns(qw/user address/);
1132 __PACKAGE__->set_primary_key(qw/user address/);
1133 __PACKAGE__->belongs_to('user' => 'My::User');
1134 __PACKAGE__->belongs_to('address' => 'My::Address');
1136 package My::Address;
1137 use base 'DBIx::Class::Core';
1138 __PACKAGE__->table('address');
1139 __PACKAGE__->add_columns(qw/id street town area_code country/);
1140 __PACKAGE__->set_primary_key('id');
1141 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1142 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1144 $rs = $user->addresses(); # get all addresses for a user
1145 $rs = $address->users(); # get all users for an address
1147 my $address = $user->add_to_addresses( # returns a My::Address instance,
1148 # NOT a My::UserAddress instance!
1150 country => 'United Kingdom',
1157 =head2 Relationships across DB schemas
1159 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1160 is easy as long as the schemas themselves are all accessible via the same DBI
1161 connection. In most cases, this means that they are on the same database host
1162 as each other and your connecting database user has the proper permissions to them.
1164 To accomplish this one only needs to specify the DB schema name in the table
1165 declaration, like so...
1167 package MyApp::Schema::Result::Artist;
1168 use base qw/DBIx::Class::Core/;
1170 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1172 __PACKAGE__->add_columns(qw/ artist_id name /);
1173 __PACKAGE__->set_primary_key('artist_id');
1174 __PACKAGE__->has_many('cds' => 'MyApp::Schema::Result::Cd');
1178 Whatever string you specify there will be used to build the "FROM" clause in SQL
1181 The big drawback to this is you now have DB schema names hardcoded in your
1182 class files. This becomes especially troublesome if you have multiple instances
1183 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1184 the DB schemas are named based on the environment (e.g. database1_dev).
1186 However, one can dynamically "map" to the proper DB schema by overriding the
1187 L<connection|DBIx::Class::Schema/connection> method in your Schema class and
1188 building a renaming facility, like so:
1190 package MyApp::Schema;
1193 extends 'DBIx::Class::Schema';
1195 around connection => sub {
1196 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1198 my $postfix = delete $attr->{schema_name_postfix};
1203 $self->append_db_name($postfix);
1207 sub append_db_name {
1208 my ( $self, $postfix ) = @_;
1212 { $_->name =~ /^\w+\./mx }
1214 { $self->source($_) }
1217 foreach my $source (@sources_with_db) {
1218 my $name = $source->name;
1219 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1221 $source->name($name);
1227 By overriding the L<connection|DBIx::Class::Schema/connection>
1228 method and extracting a custom option from the provided \%attr hashref one can
1229 then simply iterate over all the Schema's ResultSources, renaming them as
1232 To use this facility, simply add or modify the \%attr hashref that is passed to
1233 L<connection|DBIx::Class::Schema/connect>, as follows:
1236 = MyApp::Schema->connect(
1241 schema_name_postfix => '_dev'
1242 # ... Other options as desired ...
1245 Obviously, one could accomplish even more advanced mapping via a hash map or a
1250 =head2 Transactions with txn_do
1252 As of version 0.04001, there is improved transaction support in
1253 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1254 example of the recommended way to use it:
1256 my $genus = $schema->resultset('Genus')->find(12);
1258 my $coderef2 = sub {
1263 my $coderef1 = sub {
1264 $genus->add_to_species({ name => 'troglodyte' });
1267 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1268 return $genus->species;
1274 $rs = $schema->txn_do($coderef1);
1276 # Transaction failed
1277 die "the sky is falling!" #
1278 if ($_ =~ /Rollback failed/); # Rollback failed
1280 deal_with_failed_transaction();
1283 Note: by default C<txn_do> will re-run the coderef one more time if an
1284 error occurs due to client disconnection (e.g. the server is bounced).
1285 You need to make sure that your coderef can be invoked multiple times
1286 without terrible side effects.
1288 Nested transactions will work as expected. That is, only the outermost
1289 transaction will actually issue a commit to the $dbh, and a rollback
1290 at any level of any transaction will cause the entire nested
1291 transaction to fail.
1293 =head2 Nested transactions and auto-savepoints
1295 If savepoints are supported by your RDBMS, it is possible to achieve true
1296 nested transactions with minimal effort. To enable auto-savepoints via nested
1297 transactions, supply the C<< auto_savepoint = 1 >> connection attribute.
1299 Here is an example of true nested transactions. In the example, we start a big
1300 task which will create several rows. Generation of data for each row is a
1301 fragile operation and might fail. If we fail creating something, depending on
1302 the type of failure, we want to abort the whole task, or only skip the failed
1305 my $schema = MySchema->connect("dbi:Pg:dbname=my_db");
1307 # Start a transaction. Every database change from here on will only be
1308 # committed into the database if the try block succeeds.
1312 $schema->txn_do(sub {
1315 my $job = $schema->resultset('Job')->create({ name=> 'big job' });
1316 # SQL: INSERT INTO job ( name) VALUES ( 'big job' );
1320 # Start a nested transaction, which in fact sets a savepoint.
1322 $schema->txn_do(sub {
1323 # SQL: SAVEPOINT savepoint_0;
1325 my $thing = $schema->resultset('Thing')->create({ job=>$job->id });
1326 # SQL: INSERT INTO thing ( job) VALUES ( 1 );
1329 # This will generate an error, thus setting $@
1331 $thing->update({force_fail=>'foo'});
1332 # SQL: UPDATE thing SET force_fail = 'foo'
1333 # WHERE ( id = 42 );
1337 # SQL: ROLLBACK TO SAVEPOINT savepoint_0;
1339 # There was an error while creating a $thing. Depending on the error
1340 # we want to abort the whole transaction, or only rollback the
1341 # changes related to the creation of this $thing
1343 # Abort the whole job
1344 if ($_ =~ /horrible_problem/) {
1345 print "something horrible happend, aborting job!";
1346 die $_; # rethrow error
1349 # Ignore this $thing, report the error, and continue with the
1351 print "Cannot create thing: $_";
1353 # There was no error, so save all changes since the last
1356 # SQL: RELEASE SAVEPOINT savepoint_0;
1364 # There was an error while handling the $job. Rollback all changes
1365 # since the transaction started, including the already committed
1366 # ('released') savepoints. There will be neither a new $job nor any
1367 # $thing entry in the database.
1371 print "ERROR: $exception\n";
1374 # There was no error while handling the $job. Commit all changes.
1375 # Only now other connections can see the newly created $job and
1383 In this example it might be hard to see where the rollbacks, releases and
1384 commits are happening, but it works just the same as for plain
1385 L<txn_do|DBIx::Class::Storage/txn_do>: If the L<try|Try::Tiny/try>-block
1386 around L<txn_do|DBIx::Class::Storage/txn_do> fails, a rollback is issued.
1387 If the L<try|Try::Tiny/try> succeeds, the transaction is committed
1388 (or the savepoint released).
1390 While you can get more fine-grained control using C<svp_begin>, C<svp_release>
1391 and C<svp_rollback>, it is strongly recommended to use C<txn_do> with coderefs.
1393 =head2 Simple Transactions with DBIx::Class::Storage::TxnScopeGuard
1395 An easy way to use transactions is with
1396 L<DBIx::Class::Storage::TxnScopeGuard>. See L</Automatically creating
1397 related objects> for an example.
1399 Note that unlike txn_do, TxnScopeGuard will only make sure the connection is
1400 alive when issuing the C<BEGIN> statement. It will not (and really can not)
1401 retry if the server goes away mid-operations, unlike C<txn_do>.
1405 =head2 Creating Schemas From An Existing Database
1407 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1408 L<DBIx::Class::Schema> and associated sources by examining the database.
1410 The recommend way of achieving this is to use the L<dbicdump> utility or the
1411 L<Catalyst> helper, as described in
1412 L<Manual::Intro|DBIx::Class::Manual::Intro/Using DBIx::Class::Schema::Loader>.
1414 Alternatively, use the
1415 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1417 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1418 -e 'make_schema_at("My::Schema", \
1419 { db_schema => 'myschema', components => ["InflateColumn::DateTime"] }, \
1420 [ "dbi:Pg:dbname=foo", "username", "password" ])'
1422 This will create a tree of files rooted at C<./lib/My/Schema/> containing source
1423 definitions for all the tables found in the C<myschema> schema in the C<foo>
1426 =head2 Creating DDL SQL
1428 The following functionality requires you to have L<SQL::Translator>
1429 (also known as "SQL Fairy") installed.
1431 To create a set of database-specific .sql files for the above schema:
1433 my $schema = My::Schema->connect($dsn);
1434 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1439 By default this will create schema files in the current directory, for
1440 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1442 To create a new database using the schema:
1444 my $schema = My::Schema->connect($dsn);
1445 $schema->deploy({ add_drop_table => 1});
1447 To import created .sql files using the mysql client:
1449 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1451 To create C<ALTER TABLE> conversion scripts to update a database to a
1452 newer version of your schema at a later point, first set a new
1453 C<$VERSION> in your Schema file, then:
1455 my $schema = My::Schema->connect($dsn);
1456 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1462 This will produce new database-specific .sql files for the new version
1463 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1464 requires that the files for 0.1 as created above are available in the
1465 given directory to diff against.
1467 =head2 Select from dual
1469 Dummy tables are needed by some databases to allow calling functions
1470 or expressions that aren't based on table content, for examples of how
1471 this applies to various database types, see:
1472 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1474 Note: If you're using Oracles dual table don't B<ever> do anything
1475 other than a select, if you CRUD on your dual table you *will* break
1478 Make a table class as you would for any other table
1480 package MyAppDB::Dual;
1483 use base 'DBIx::Class::Core';
1484 __PACKAGE__->table("Dual");
1485 __PACKAGE__->add_columns(
1487 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1490 Once you've loaded your table class select from it using C<select>
1491 and C<as> instead of C<columns>
1493 my $rs = $schema->resultset('Dual')->search(undef,
1494 { select => [ 'sydate' ],
1499 All you have to do now is be careful how you access your resultset, the below
1500 will not work because there is no column called 'now' in the Dual table class
1502 while (my $dual = $rs->next) {
1503 print $dual->now."\n";
1505 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1507 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1508 your Dual class for whatever you wanted to select from dual, but that's just
1509 silly, instead use C<get_column>
1511 while (my $dual = $rs->next) {
1512 print $dual->get_column('now')."\n";
1517 my $cursor = $rs->cursor;
1518 while (my @vals = $cursor->next) {
1519 print $vals[0]."\n";
1522 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1523 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1524 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1525 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1526 L<SQL::Translator> to not create table dual:
1529 add_drop_table => 1,
1530 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1532 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1534 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1536 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1537 while ( my $dual = $rs->next ) {
1538 print $dual->{now}."\n";
1541 Here are some example C<select> conditions to illustrate the different syntax
1542 you could use for doing stuff like
1543 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1545 # get a sequence value
1546 select => [ 'A_SEQ.nextval' ],
1548 # get create table sql
1549 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1551 # get a random num between 0 and 100
1552 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1555 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1558 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1560 # which day of the week were you born on?
1561 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1563 # select 16 rows from dual
1564 select => [ "'hello'" ],
1566 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1570 =head2 Adding Indexes And Functions To Your SQL
1572 Often you will want indexes on columns on your table to speed up searching. To
1573 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1574 class (refer to the advanced
1575 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1576 to share a hook between multiple sources):
1578 package My::Schema::Result::Artist;
1580 __PACKAGE__->table('artist');
1581 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1583 sub sqlt_deploy_hook {
1584 my ($self, $sqlt_table) = @_;
1586 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1591 Sometimes you might want to change the index depending on the type of the
1592 database for which SQL is being generated:
1594 my ($db_type = $sqlt_table->schema->translator->producer_type)
1595 =~ s/^SQL::Translator::Producer:://;
1597 You can also add hooks to the schema level to stop certain tables being
1604 sub sqlt_deploy_hook {
1605 my ($self, $sqlt_schema) = @_;
1607 $sqlt_schema->drop_table('table_name');
1610 You could also add views, procedures or triggers to the output using
1611 L<SQL::Translator::Schema/add_view>,
1612 L<SQL::Translator::Schema/add_procedure> or
1613 L<SQL::Translator::Schema/add_trigger>.
1616 =head2 Schema versioning
1618 The following example shows simplistically how you might use DBIx::Class to
1619 deploy versioned schemas to your customers. The basic process is as follows:
1625 Create a DBIx::Class schema
1637 Modify schema to change functionality
1641 Deploy update to customers
1645 B<Create a DBIx::Class schema>
1647 This can either be done manually, or generated from an existing database as
1648 described under L</Creating Schemas From An Existing Database>
1652 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1654 B<Deploy to customers>
1656 There are several ways you could deploy your schema. These are probably
1657 beyond the scope of this recipe, but might include:
1663 Require customer to apply manually using their RDBMS.
1667 Package along with your app, making database dump/schema update/tests
1668 all part of your install.
1672 B<Modify the schema to change functionality>
1674 As your application evolves, it may be necessary to modify your schema
1675 to change functionality. Once the changes are made to your schema in
1676 DBIx::Class, export the modified schema and the conversion scripts as
1677 in L</Creating DDL SQL>.
1679 B<Deploy update to customers>
1681 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1682 Schema class. This will add a new table to your database called
1683 C<dbix_class_schema_vesion> which will keep track of which version is installed
1684 and warn if the user tries to run a newer schema version than the
1685 database thinks it has.
1687 Alternatively, you can send the conversion SQL scripts to your
1690 =head2 Setting quoting for the generated SQL
1692 If the database contains column names with spaces and/or reserved words, they
1693 need to be quoted in the SQL queries. This is done using:
1695 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1696 $schema->storage->sql_maker->name_sep('.');
1698 The first sets the quote characters. Either a pair of matching
1699 brackets, or a C<"> or C<'>:
1701 $schema->storage->sql_maker->quote_char('"');
1703 Check the documentation of your database for the correct quote
1704 characters to use. C<name_sep> needs to be set to allow the SQL
1705 generator to put the quotes the correct place, and defaults to
1706 C<.> if not supplied.
1708 In most cases you should set these as part of the arguments passed to
1709 L<DBIx::Class::Schema/connect>:
1711 my $schema = My::Schema->connect(
1721 In some cases, quoting will be required for all users of a schema. To enforce
1722 this, you can also overload the C<connection> method for your schema class:
1726 my $rv = $self->next::method( @_ );
1727 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1728 $rv->storage->sql_maker->name_sep('.');
1732 =head2 Working with PostgreSQL array types
1734 You can also assign values to PostgreSQL array columns by passing array
1735 references in the C<\%columns> (C<\%vals>) hashref of the
1736 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1739 $resultset->create({
1740 numbers => [1, 2, 3]
1745 numbers => [1, 2, 3]
1752 In conditions (e.g. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1753 methods) you cannot directly use array references (since this is interpreted as
1754 a list of values to be C<OR>ed), but you can use the following syntax to force
1755 passing them as bind values:
1759 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1763 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1764 placeholders and bind values (subqueries)> for more explanation. Note that
1765 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1766 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1767 arrayrefs together with the column name, like this:
1768 C<< [column_name => value] >>.
1770 =head2 Formatting DateTime objects in queries
1772 To ensure C<WHERE> conditions containing L<DateTime> arguments are properly
1773 formatted to be understood by your RDBMS, you must use the C<DateTime>
1774 formatter returned by L<DBIx::Class::Storage::DBI/datetime_parser> to format
1775 any L<DateTime> objects you pass to L<search|DBIx::Class::ResultSet/search>
1776 conditions. Any L<Storage|DBIx::Class::Storage> object attached to your
1777 L<Schema|DBIx::Class::Schema> provides a correct C<DateTime> formatter, so
1778 all you have to do is:
1780 my $dtf = $schema->storage->datetime_parser;
1781 my $rs = $schema->resultset('users')->search(
1785 $dtf->format_datetime($dt_start),
1786 $dtf->format_datetime($dt_end),
1792 Without doing this the query will contain the simple stringification of the
1793 C<DateTime> object, which almost never matches the RDBMS expectations.
1795 This kludge is necessary only for conditions passed to
1796 L<DBIx::Class::ResultSet/search>, whereas
1797 L<create|DBIx::Class::ResultSet/create>,
1798 L<find|DBIx::Class::ResultSet/find>,
1799 L<DBIx::Class::Row/update> (but not L<DBIx::Class::ResultSet/update>) are all
1800 L<DBIx::Class::InflateColumn>-aware and will do the right thing when supplied
1801 an inflated C<DateTime> object.
1803 =head2 Using Unicode
1805 When using unicode character data there are two alternatives -
1806 either your database supports unicode characters (including setting
1807 the utf8 flag on the returned string), or you need to encode/decode
1808 data appropriately each time a string field is inserted into or
1809 retrieved from the database. It is better to avoid
1810 encoding/decoding data and to use your database's own unicode
1811 capabilities if at all possible.
1813 The L<DBIx::Class::UTF8Columns> component handles storing selected
1814 unicode columns in a database that does not directly support
1815 unicode. If used with a database that does correctly handle unicode
1816 then strange and unexpected data corrupt B<will> occur.
1818 The Catalyst Wiki Unicode page at
1819 L<http://wiki.catalystframework.org/wiki/tutorialsandhowtos/using_unicode>
1820 has additional information on the use of Unicode with Catalyst and
1823 The following databases do correctly handle unicode data:-
1827 MySQL supports unicode, and will correctly flag utf8 data from the
1828 database if the C<mysql_enable_utf8> is set in the connect options.
1830 my $schema = My::Schema->connection('dbi:mysql:dbname=test',
1832 { mysql_enable_utf8 => 1} );
1835 When set, a data retrieved from a textual column type (char,
1836 varchar, etc) will have the UTF-8 flag turned on if necessary. This
1837 enables character semantics on that string. You will also need to
1838 ensure that your database / table / column is configured to use
1839 UTF8. See Chapter 10 of the mysql manual for details.
1841 See L<DBD::mysql> for further details.
1845 Information about Oracle support for unicode can be found in
1846 L<DBD::Oracle/UNICODE>.
1850 PostgreSQL supports unicode if the character set is correctly set
1851 at database creation time. Additionally the C<pg_enable_utf8>
1852 should be set to ensure unicode data is correctly marked.
1854 my $schema = My::Schema->connection('dbi:Pg:dbname=test',
1856 { pg_enable_utf8 => 1} );
1858 Further information can be found in L<DBD::Pg>.
1862 SQLite version 3 and above natively use unicode internally. To
1863 correctly mark unicode strings taken from the database, the
1864 C<sqlite_unicode> flag should be set at connect time (in versions
1865 of L<DBD::SQLite> prior to 1.27 this attribute was named
1868 my $schema = My::Schema->connection('dbi:SQLite:/tmp/test.db',
1870 { sqlite_unicode => 1} );
1872 =head1 BOOTSTRAPPING/MIGRATING
1874 =head2 Easy migration from class-based to schema-based setup
1876 You want to start using the schema-based approach to L<DBIx::Class>
1877 (see L<DBIx::Class::Manual::Intro/Setting it up manually>), but have an
1878 established class-based setup with lots of existing classes that you don't
1879 want to move by hand. Try this nifty script instead:
1882 use SQL::Translator;
1884 my $schema = MyDB->schema_instance;
1886 my $translator = SQL::Translator->new(
1887 debug => $debug || 0,
1888 trace => $trace || 0,
1889 no_comments => $no_comments || 0,
1890 show_warnings => $show_warnings || 0,
1891 add_drop_table => $add_drop_table || 0,
1892 validate => $validate || 0,
1894 'DBIx::Schema' => $schema,
1897 'prefix' => 'My::Schema',
1901 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1902 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1904 my $output = $translator->translate(@args) or die
1905 "Error: " . $translator->error;
1909 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1910 namespace, which is currently left as an exercise for the reader.
1912 =head1 OVERLOADING METHODS
1914 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1915 method calls, useful for things like default values and triggers. You have to
1916 use calls to C<next::method> to overload methods. More information on using
1917 L<Class::C3> with L<DBIx::Class> can be found in
1918 L<DBIx::Class::Manual::Component>.
1920 =head2 Setting default values for a row
1922 It's as simple as overriding the C<new> method. Note the use of
1926 my ( $class, $attrs ) = @_;
1928 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1930 my $new = $class->next::method($attrs);
1935 For more information about C<next::method>, look in the L<Class::C3>
1936 documentation. See also L<DBIx::Class::Manual::Component> for more
1937 ways to write your own base classes to do this.
1939 People looking for ways to do "triggers" with DBIx::Class are probably
1940 just looking for this.
1942 =head2 Changing one field whenever another changes
1944 For example, say that you have three columns, C<id>, C<number>, and
1945 C<squared>. You would like to make changes to C<number> and have
1946 C<squared> be automagically set to the value of C<number> squared.
1947 You can accomplish this by wrapping the C<number> accessor with the C<around>
1948 method modifier, available through either L<Class::Method::Modifiers>,
1949 L<Moose|Moose::Manual::MethodModifiers> or L<Moose-like|Moo> modules):
1951 around number => sub {
1952 my ($orig, $self) = (shift, shift);
1956 $self->squared( $value * $value );
1962 Note that the hard work is done by the call to C<< $self->$orig >>, which
1963 redispatches your call to store_column in the superclass(es).
1965 Generally, if this is a calculation your database can easily do, try
1966 and avoid storing the calculated value, it is safer to calculate when
1967 needed, than rely on the data being in sync.
1969 =head2 Automatically creating related objects
1971 You might have a class C<Artist> which has many C<CD>s. Further, you
1972 want to create a C<CD> object every time you insert an C<Artist> object.
1973 You can accomplish this by overriding C<insert> on your objects:
1976 my ( $self, @args ) = @_;
1977 $self->next::method(@args);
1978 $self->create_related ('cds', \%initial_cd_data );
1982 If you want to wrap the two inserts in a transaction (for consistency,
1983 an excellent idea), you can use the awesome
1984 L<DBIx::Class::Storage::TxnScopeGuard>:
1987 my ( $self, @args ) = @_;
1989 my $guard = $self->result_source->schema->txn_scope_guard;
1991 $self->next::method(@args);
1992 $self->create_related ('cds', \%initial_cd_data );
2000 =head2 Wrapping/overloading a column accessor
2004 Say you have a table "Camera" and want to associate a description
2005 with each camera. For most cameras, you'll be able to generate the description from
2006 the other columns. However, in a few special cases you may want to associate a
2007 custom description with a camera.
2011 In your database schema, define a description field in the "Camera" table that
2012 can contain text and null values.
2014 In DBIC, we'll overload the column accessor to provide a sane default if no
2015 custom description is defined. The accessor will either return or generate the
2016 description, depending on whether the field is null or not.
2018 First, in your "Camera" schema class, define the description field as follows:
2020 __PACKAGE__->add_columns(description => { accessor => '_description' });
2022 Next, we'll define the accessor-wrapper subroutine:
2027 # If there is an update to the column, we'll let the original accessor
2029 return $self->_description(@_) if @_;
2031 # Fetch the column value.
2032 my $description = $self->_description;
2034 # If there's something in the description field, then just return that.
2035 return $description if defined $description && length $descripton;
2037 # Otherwise, generate a description.
2038 return $self->generate_description;
2041 =head1 DEBUGGING AND PROFILING
2043 =head2 DBIx::Class objects with Data::Dumper
2045 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
2046 be hard to find the pertinent data in all the data it can generate.
2047 Specifically, if one naively tries to use it like so,
2051 my $cd = $schema->resultset('CD')->find(1);
2054 several pages worth of data from the CD object's schema and result source will
2055 be dumped to the screen. Since usually one is only interested in a few column
2056 values of the object, this is not very helpful.
2058 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
2059 it. Simply define a hook that L<Data::Dumper> will call on the object before
2060 dumping it. For example,
2067 result_source => undef,
2075 local $Data::Dumper::Freezer = '_dumper_hook';
2077 my $cd = $schema->resultset('CD')->find(1);
2079 # dumps $cd without its ResultSource
2081 If the structure of your schema is such that there is a common base class for
2082 all your table classes, simply put a method similar to C<_dumper_hook> in the
2083 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
2084 will automagically clean up your data before printing it. See
2085 L<Data::Dumper/EXAMPLES> for more information.
2089 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
2090 executed as well as notifications of query completion and transaction
2091 begin/commit. If you'd like to profile the SQL you can subclass the
2092 L<DBIx::Class::Storage::Statistics> class and write your own profiling
2095 package My::Profiler;
2098 use base 'DBIx::Class::Storage::Statistics';
2100 use Time::HiRes qw(time);
2109 $self->print("Executing $sql: ".join(', ', @params)."\n");
2118 my $elapsed = sprintf("%0.4f", time() - $start);
2119 $self->print("Execution took $elapsed seconds.\n");
2125 You can then install that class as the debugging object:
2127 __PACKAGE__->storage->debugobj(new My::Profiler());
2128 __PACKAGE__->storage->debug(1);
2130 A more complicated example might involve storing each execution of SQL in an
2138 my $elapsed = time() - $start;
2139 push(@{ $calls{$sql} }, {
2145 You could then create average, high and low execution times for an SQL
2146 statement and dig down to see if certain parameters cause aberrant behavior.
2147 You might want to check out L<DBIx::Class::QueryLog> as well.
2149 =head1 IMPROVING PERFORMANCE
2155 Install L<Class::XSAccessor> to speed up L<Class::Accessor::Grouped>.
2159 On Perl 5.8 install L<Class::C3::XS>.
2163 L<prefetch|DBIx::Class::ResultSet/prefetch> relationships, where possible. See
2164 L</Using joins and prefetch>.
2168 Use L<populate|DBIx::Class::ResultSet/populate> in void context to insert data
2169 when you don't need the resulting L<result|DBIx::Class::Manual::ResultClass> objects,
2170 if possible, but see the caveats.
2172 When inserting many rows, for best results, populate a large number of rows at a
2173 time, but not so large that the table is locked for an unacceptably long time.
2175 If using L<create|DBIx::Class::ResultSet/create> instead, use a transaction and
2176 commit every C<X> rows; where C<X> gives you the best performance without
2177 locking the table for too long.
2181 When selecting many rows, if you don't need full-blown L<DBIx::Class::Row>
2182 objects, consider using L<DBIx::Class::ResultClass::HashRefInflator>.
2186 See also L</STARTUP SPEED> and L</MEMORY USAGE> in this document.
2190 =head1 STARTUP SPEED
2192 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
2193 as the ORM loads all the relevant classes. This section examines
2194 techniques for reducing the startup delay.
2196 These tips are listed in order of decreasing effectiveness - so the
2197 first tip, if applicable, should have the greatest effect on your
2200 =head2 Statically Define Your Schema
2203 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
2204 classes dynamically based on the database schema then there will be a
2205 significant startup delay.
2207 For production use a statically defined schema (which can be generated
2208 using L<DBIx::Class::Schema::Loader> to dump the database schema once - see
2209 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
2210 L<dump_directory|DBIx::Class::Schema::Loader::Base/dump_directory> for more
2211 details on creating static schemas from a database).
2213 =head2 Move Common Startup into a Base Class
2215 Typically L<DBIx::Class> result classes start off with
2217 use base qw/DBIx::Class::Core/;
2218 __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
2220 If this preamble is moved into a common base class:-
2224 use base qw/DBIx::Class::Core/;
2225 __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
2228 and each result class then uses this as a base:-
2230 use base qw/MyDBICbase/;
2232 then the load_components is only performed once, which can result in a
2233 considerable startup speedup for schemas with many classes.
2235 =head2 Explicitly List Schema Result Classes
2237 The schema class will normally contain
2239 __PACKAGE__->load_classes();
2241 to load the result classes. This will use L<Module::Find|Module::Find>
2242 to find and load the appropriate modules. Explicitly defining the
2243 classes you wish to load will remove the overhead of
2244 L<Module::Find|Module::Find> and the related directory operations:
2246 __PACKAGE__->load_classes(qw/ CD Artist Track /);
2248 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
2249 syntax to load the appropriate classes there is not a direct alternative
2250 avoiding L<Module::Find|Module::Find>.
2254 =head2 Cached statements
2256 L<DBIx::Class> normally caches all statements with
2257 L<prepare_cached()|DBI/prepare_cached>. This is normally a good idea, but if
2258 too many statements are cached, the database may use too much memory and may
2259 eventually run out and fail entirely. If you suspect this may be the case,
2260 you may want to examine DBI's L<CachedKids|DBI/CachedKids> hash:
2262 # print all currently cached prepared statements
2263 print for keys %{$schema->storage->dbh->{CachedKids}};
2264 # get a count of currently cached prepared statements
2265 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
2267 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
2270 my $kids = $schema->storage->dbh->{CachedKids};
2271 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
2273 But what you probably want is to expire unused statements and not those that are used frequently.
2274 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
2278 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
2279 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },
2284 =head1 FURTHER QUESTIONS?
2286 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
2288 =head1 COPYRIGHT AND LICENSE
2290 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
2291 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
2292 redistribute it and/or modify it under the same terms as the
2293 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.