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 You can get a L<Data::Page> object for the resultset (suitable for use
23 in e.g. a template) using the C<pager> method:
27 =head2 Complex WHERE clauses
29 Sometimes you need to formulate a query using specific operators:
31 my @albums = $schema->resultset('Album')->search({
32 artist => { 'like', '%Lamb%' },
33 title => { 'like', '%Fear of Fours%' },
36 This results in something like the following C<WHERE> clause:
38 WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
40 Other queries might require slightly more complex logic:
42 my @albums = $schema->resultset('Album')->search({
45 artist => { 'like', '%Smashing Pumpkins%' },
46 title => 'Siamese Dream',
48 artist => 'Starchildren',
52 This results in the following C<WHERE> clause:
54 WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
55 OR artist = 'Starchildren'
57 For more information on generating complex queries, see
58 L<SQL::Abstract/WHERE CLAUSES>.
60 =head2 Retrieve one and only one row from a resultset
62 Sometimes you need only the first "top" row of a resultset. While this can be
63 easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal,
64 as a full blown cursor for the resultset will be created and then immediately
65 destroyed after fetching the first row object.
66 L<< $rs->single|DBIx::Class::ResultSet/single >> is
67 designed specifically for this case - it will grab the first returned result
68 without even instantiating a cursor.
70 Before replacing all your calls to C<first()> with C<single()> please observe the
76 While single() takes a search condition just like search() does, it does
77 _not_ accept search attributes. However one can always chain a single() to
80 my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single;
84 Since single() is the engine behind find(), it is designed to fetch a
85 single row per database query. Thus a warning will be issued when the
86 underlying SELECT returns more than one row. Sometimes however this usage
87 is valid: i.e. we have an arbitrary number of cd's but only one of them is
88 at the top of the charts at any given time. If you know what you are doing,
89 you can silence the warning by explicitly limiting the resultset size:
91 my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single;
95 =head2 Arbitrary SQL through a custom ResultSource
97 Sometimes you have to run arbitrary SQL because your query is too complex
98 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
99 be optimized for your database in a special way, but you still want to
100 get the results as a L<DBIx::Class::ResultSet>.
101 The recommended way to accomplish this is by defining a separate ResultSource
102 for your query. You can then inject complete SQL statements using a scalar
103 reference (this is a feature of L<SQL::Abstract>).
105 Say you want to run a complex custom query on your user data, here's what
106 you have to add to your User class:
108 package My::Schema::Result::User;
110 use base qw/DBIx::Class/;
112 # ->load_components, ->table, ->add_columns, etc.
114 # Make a new ResultSource based on the User class
115 my $source = __PACKAGE__->result_source_instance();
116 my $new_source = $source->new( $source );
117 $new_source->source_name( 'UserFriendsComplex' );
119 # Hand in your query as a scalar reference
120 # It will be added as a sub-select after FROM,
121 # so pay attention to the surrounding brackets!
122 $new_source->name( \<<SQL );
123 ( SELECT u.* FROM user u
124 INNER JOIN user_friends f ON u.id = f.user_id
125 WHERE f.friend_user_id = ?
127 SELECT u.* FROM user u
128 INNER JOIN user_friends f ON u.id = f.friend_user_id
129 WHERE f.user_id = ? )
132 # Finally, register your new ResultSource with your Schema
133 My::Schema->register_extra_source( 'UserFriendsComplex' => $new_source );
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, ie. cannot call L</update>,
145 L</delete>, ... on it).
147 If you prefer to have the definitions of these custom ResultSources in separate
148 files (instead of stuffing all of them into the same ResultSource class), you
149 can achieve the same with subclassing the ResultSource class and defining the
150 new ResultSource there:
152 package My::Schema::Result::UserFriendsComplex;
154 use base qw/My::Schema::Result::User/;
156 __PACKAGE__->table('dummy'); # currently must be called before anything else
158 # Hand in your query as a scalar reference
159 # It will be added as a sub-select after FROM,
160 # so pay attention to the surrounding brackets!
161 __PACKAGE__->result_source_instance->name( \<<SQL );
162 ( SELECT u.* FROM user u
163 INNER JOIN user_friends f ON u.id = f.user_id
164 WHERE f.friend_user_id = ?
166 SELECT u.* FROM user u
167 INNER JOIN user_friends f ON u.id = f.friend_user_id
168 WHERE f.user_id = ? )
175 =head2 Using specific columns
177 When you only want specific columns from a table, you can use
178 C<columns> to specify which ones you need. This is useful to avoid
179 loading columns with large amounts of data that you aren't about to
182 my $rs = $schema->resultset('Artist')->search(
185 columns => [qw/ name /]
190 # SELECT artist.name FROM artist
192 This is a shortcut for C<select> and C<as>, see below. C<columns>
193 cannot be used together with C<select> and C<as>.
195 =head2 Using database functions or stored procedures
197 The combination of C<select> and C<as> can be used to return the result of a
198 database function or stored procedure as a column value. You use C<select> to
199 specify the source for your column value (e.g. a column name, function, or
200 stored procedure name). You then use C<as> to set the column name you will use
201 to access the returned value:
203 my $rs = $schema->resultset('Artist')->search(
206 select => [ 'name', { LENGTH => 'name' } ],
207 as => [qw/ name name_length /],
212 # SELECT name name, LENGTH( name )
215 Note that the C< as > attribute has absolutely nothing to with the sql
216 syntax C< SELECT foo AS bar > (see the documentation in
217 L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
218 column in your base class (i.e. it was added with C<add_columns>), you
219 just access it as normal. Our C<Artist> class has a C<name> column, so
220 we just use the C<name> accessor:
222 my $artist = $rs->first();
223 my $name = $artist->name();
225 If on the other hand the alias does not correspond to an existing column, you
226 have to fetch the value using the C<get_column> accessor:
228 my $name_length = $artist->get_column('name_length');
230 If you don't like using C<get_column>, you can always create an accessor for
231 any of your aliases using either of these:
233 # Define accessor manually:
234 sub name_length { shift->get_column('name_length'); }
236 # Or use DBIx::Class::AccessorGroup:
237 __PACKAGE__->mk_group_accessors('column' => 'name_length');
239 =head2 SELECT DISTINCT with multiple columns
241 my $rs = $schema->resultset('Artist')->search(
244 columns => [ qw/artist_id name rank/ ],
249 my $rs = $schema->resultset('Artist')->search(
252 columns => [ qw/artist_id name rank/ ],
253 group_by => [ qw/artist_id name rank/ ],
258 # SELECT me.artist_id, me.name, me.rank
260 # GROUP BY artist_id, name, rank
262 =head2 SELECT COUNT(DISTINCT colname)
264 my $rs = $schema->resultset('Artist')->search(
267 columns => [ qw/name/ ],
272 my $rs = $schema->resultset('Artist')->search(
275 columns => [ qw/name/ ],
276 group_by => [ qw/name/ ],
280 my $count = $rs->count;
283 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
285 =head2 Grouping results
287 L<DBIx::Class> supports C<GROUP BY> as follows:
289 my $rs = $schema->resultset('Artist')->search(
293 select => [ 'name', { count => 'cds.id' } ],
294 as => [qw/ name cd_count /],
295 group_by => [qw/ name /]
300 # SELECT name, COUNT( cd.id ) FROM artist
301 # LEFT JOIN cd ON artist.id = cd.artist
304 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
305 are in any way unsure about the use of the attributes above (C< join
306 >, C< select >, C< as > and C< group_by >).
308 =head2 Subqueries (EXPERIMENTAL)
310 You can write subqueries relatively easily in DBIC.
312 my $inside_rs = $schema->resultset('Artist')->search({
313 name => [ 'Billy Joel', 'Brittany Spears' ],
316 my $rs = $schema->resultset('CD')->search({
317 artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
320 The usual operators ( =, !=, IN, NOT IN, etc) are supported.
322 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
323 The following will B<not> work:
325 my $rs = $schema->resultset('CD')->search({
326 artist_id => $inside_rs->get_column('id')->as_query,
331 Subqueries are supported in the where clause (first hashref), and in the
332 from, select, and +select attributes.
334 =head3 Correlated subqueries
336 my $cdrs = $schema->resultset('CD');
337 my $rs = $cdrs->search({
339 '=' => $cdrs->search(
340 { artist_id => { '=' => \'me.artist_id' } },
342 )->get_column('year')->max_rs->as_query,
346 That creates the following SQL:
348 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
351 SELECT MAX(inner.year)
353 WHERE artist_id = me.artist_id
358 Please note that subqueries are considered an experimental feature.
360 =head2 Predefined searches
362 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
363 and defining often used searches as methods:
365 package My::DBIC::ResultSet::CD;
368 use base 'DBIx::Class::ResultSet';
370 sub search_cds_ordered {
373 return $self->search(
375 { order_by => 'name DESC' },
381 To use your resultset, first tell DBIx::Class to create an instance of it
382 for you, in your My::DBIC::Schema::CD class:
384 # class definition as normal
385 __PACKAGE__->load_components(qw/ Core /);
386 __PACKAGE__->table('cd');
388 # tell DBIC to use the custom ResultSet class
389 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
391 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
393 Then call your new method in your code:
395 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
397 =head2 Using SQL functions on the left hand side of a comparison
399 Using SQL functions on the left hand side of a comparison is generally
400 not a good idea since it requires a scan of the entire table. However,
401 it can be accomplished with C<DBIx::Class> when necessary.
403 If you do not have quoting on, simply include the function in your search
404 specification as you would any column:
406 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
408 With quoting on, or for a more portable solution, use the C<where>
411 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
415 (When the bind args ordering bug is fixed, this technique will be better
416 and can replace the one above.)
418 With quoting on, or for a more portable solution, use the C<where> and
422 where => \'YEAR(date_of_birth) = ?',
428 =head1 JOINS AND PREFETCHING
430 =head2 Using joins and prefetch
432 You can use the C<join> attribute to allow searching on, or sorting your
433 results by, one or more columns in a related table.
435 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
437 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
439 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
441 my $rs = $schema->resultset('CD')->search(
443 'artists.name' => 'Bob Marley'
446 join => 'artists', # join the artist table
451 # SELECT cd.* FROM cd
452 # JOIN artist ON cd.artist = artist.id
453 # WHERE artist.name = 'Bob Marley'
455 In that example both the join, and the condition use the relationship name rather than the table name
456 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
458 If required, you can now sort on any column in the related tables by including
459 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
461 my $rs = $schema->resultset('CD')->search(
463 'artists.name' => 'Bob Marley'
467 order_by => [qw/ artists.name /]
472 # SELECT cd.* FROM cd
473 # JOIN artist ON cd.artist = artist.id
474 # WHERE artist.name = 'Bob Marley'
475 # ORDER BY artist.name
477 Note that the C<join> attribute should only be used when you need to search or
478 sort using columns in a related table. Joining related tables when you only
479 need columns from the main table will make performance worse!
481 Now let's say you want to display a list of CDs, each with the name of the
482 artist. The following will work fine:
484 while (my $cd = $rs->next) {
485 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
488 There is a problem however. We have searched both the C<cd> and C<artist> tables
489 in our main query, but we have only returned data from the C<cd> table. To get
490 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
493 SELECT artist.* FROM artist WHERE artist.id = ?
495 A statement like the one above will run for each and every CD returned by our
496 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
499 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
500 This allows you to fetch results from related tables in advance:
502 my $rs = $schema->resultset('CD')->search(
504 'artists.name' => 'Bob Marley'
508 order_by => [qw/ artists.name /],
509 prefetch => 'artists' # return artist data too!
513 # Equivalent SQL (note SELECT from both "cd" and "artist"):
514 # SELECT cd.*, artist.* FROM cd
515 # JOIN artist ON cd.artist = artist.id
516 # WHERE artist.name = 'Bob Marley'
517 # ORDER BY artist.name
519 The code to print the CD list remains the same:
521 while (my $cd = $rs->next) {
522 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
525 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
526 so no additional SQL statements are executed. You now have a much more
529 Also note that C<prefetch> should only be used when you know you will
530 definitely use data from a related table. Pre-fetching related tables when you
531 only need columns from the main table will make performance worse!
533 =head2 Multiple joins
535 In the examples above, the C<join> attribute was a scalar. If you
536 pass an array reference instead, you can join to multiple tables. In
537 this example, we want to limit the search further, using
540 # Relationships defined elsewhere:
541 # CD->belongs_to('artist' => 'Artist');
542 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
543 my $rs = $schema->resultset('CD')->search(
545 'artist.name' => 'Bob Marley'
546 'liner_notes.notes' => { 'like', '%some text%' },
549 join => [qw/ artist liner_notes /],
550 order_by => [qw/ artist.name /],
555 # SELECT cd.*, artist.*, liner_notes.* FROM cd
556 # JOIN artist ON cd.artist = artist.id
557 # JOIN liner_notes ON cd.id = liner_notes.cd
558 # WHERE artist.name = 'Bob Marley'
559 # ORDER BY artist.name
561 =head2 Multi-step joins
563 Sometimes you want to join more than one relationship deep. In this example,
564 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
565 contain a specific string:
567 # Relationships defined elsewhere:
568 # Artist->has_many('cds' => 'CD', 'artist');
569 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
571 my $rs = $schema->resultset('Artist')->search(
573 'liner_notes.notes' => { 'like', '%some text%' },
577 'cds' => 'liner_notes'
583 # SELECT artist.* FROM artist
584 # LEFT JOIN cd ON artist.id = cd.artist
585 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
586 # WHERE liner_notes.notes LIKE '%some text%'
588 Joins can be nested to an arbitrary level. So if we decide later that we
589 want to reduce the number of Artists returned based on who wrote the liner
592 # Relationship defined elsewhere:
593 # LinerNotes->belongs_to('author' => 'Person');
595 my $rs = $schema->resultset('Artist')->search(
597 'liner_notes.notes' => { 'like', '%some text%' },
598 'author.name' => 'A. Writer'
603 'liner_notes' => 'author'
610 # SELECT artist.* FROM artist
611 # LEFT JOIN cd ON artist.id = cd.artist
612 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
613 # LEFT JOIN author ON author.id = liner_notes.author
614 # WHERE liner_notes.notes LIKE '%some text%'
615 # AND author.name = 'A. Writer'
617 =head2 Multi-step and multiple joins
619 With various combinations of array and hash references, you can join
620 tables in any combination you desire. For example, to join Artist to
621 CD and Concert, and join CD to LinerNotes:
623 # Relationships defined elsewhere:
624 # Artist->has_many('concerts' => 'Concert', 'artist');
626 my $rs = $schema->resultset('Artist')->search(
639 # SELECT artist.* FROM artist
640 # LEFT JOIN cd ON artist.id = cd.artist
641 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
642 # LEFT JOIN concert ON artist.id = concert.artist
644 =head2 Multi-step prefetch
646 C<prefetch> can be nested more than one relationship
647 deep using the same syntax as a multi-step join:
649 my $rs = $schema->resultset('Tag')->search(
659 # SELECT tag.*, cd.*, artist.* FROM tag
660 # JOIN cd ON tag.cd = cd.id
661 # JOIN artist ON cd.artist = artist.id
663 Now accessing our C<cd> and C<artist> relationships does not need additional
666 my $tag = $rs->first;
667 print $tag->cd->artist->name;
669 =head1 ROW-LEVEL OPERATIONS
671 =head2 Retrieving a row object's Schema
673 It is possible to get a Schema object from a row object like so:
675 my $schema = $cd->result_source->schema;
676 # use the schema as normal:
677 my $artist_rs = $schema->resultset('Artist');
679 This can be useful when you don't want to pass around a Schema object to every
682 =head2 Getting the value of the primary key for the last database insert
684 AKA getting last_insert_id
686 Thanks to the core component PK::Auto, this is straightforward:
688 my $foo = $rs->create(\%blah);
690 my $id = $foo->id; # foo->my_primary_key_field will also work.
692 If you are not using autoincrementing primary keys, this will probably
693 not work, but then you already know the value of the last primary key anyway.
695 =head2 Stringification
697 Employ the standard stringification technique by using the L<overload>
700 To make an object stringify itself as a single column, use something
701 like this (replace C<name> with the column/method of your choice):
703 use overload '""' => sub { shift->name}, fallback => 1;
705 For more complex stringification, you can use an anonymous subroutine:
707 use overload '""' => sub { $_[0]->name . ", " .
708 $_[0]->address }, fallback => 1;
710 =head3 Stringification Example
712 Suppose we have two tables: C<Product> and C<Category>. The table
715 Product(id, Description, category)
716 Category(id, Description)
718 C<category> is a foreign key into the Category table.
720 If you have a Product object C<$obj> and write something like
724 things will not work as expected.
726 To obtain, for example, the category description, you should add this
727 method to the class defining the Category table:
729 use overload "" => sub {
732 return $self->Description;
735 =head2 Want to know if find_or_create found or created a row?
737 Just use C<find_or_new> instead, then check C<in_storage>:
739 my $obj = $rs->find_or_new({ blah => 'blarg' });
740 unless ($obj->in_storage) {
742 # do whatever else you wanted if it was a new row
745 =head2 Static sub-classing DBIx::Class result classes
747 AKA adding additional relationships/methods/etc. to a model for a
748 specific usage of the (shared) model.
752 package My::App::Schema;
754 use base DBIx::Class::Schema;
756 # load subclassed classes from My::App::Schema::Result/ResultSet
757 __PACKAGE__->load_namespaces;
759 # load classes from shared model
761 'My::Shared::Model::Result' => [qw/
768 B<Result-Subclass definition>
770 package My::App::Schema::Result::Baz;
774 use base My::Shared::Model::Result::Baz;
776 # WARNING: Make sure you call table() again in your subclass,
777 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
778 # and the class name is not correctly registered as a source
779 __PACKAGE__->table('baz');
781 sub additional_method {
782 return "I'm an additional method only needed by this app";
787 =head2 Dynamic Sub-classing DBIx::Class proxy classes
789 AKA multi-class object inflation from one table
791 L<DBIx::Class> classes are proxy classes, therefore some different
792 techniques need to be employed for more than basic subclassing. In
793 this example we have a single user table that carries a boolean bit
794 for admin. We would like like to give the admin users
795 objects (L<DBIx::Class::Row>) the same methods as a regular user but
796 also special admin only methods. It doesn't make sense to create two
797 seperate proxy-class files for this. We would be copying all the user
798 methods into the Admin class. There is a cleaner way to accomplish
801 Overriding the C<inflate_result> method within the User proxy-class
802 gives us the effect we want. This method is called by
803 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
804 grab the object being returned, inspect the values we are looking for,
805 bless it if it's an admin object, and then return it. See the example
812 use base qw/DBIx::Class::Schema/;
814 __PACKAGE__->load_namespaces;
819 B<Proxy-Class definitions>
821 package My::Schema::Result::User;
825 use base qw/DBIx::Class/;
827 ### Define what our admin class is, for ensure_class_loaded()
828 my $admin_class = __PACKAGE__ . '::Admin';
830 __PACKAGE__->load_components(qw/Core/);
832 __PACKAGE__->table('users');
834 __PACKAGE__->add_columns(qw/user_id email password
835 firstname lastname active
838 __PACKAGE__->set_primary_key('user_id');
842 my $ret = $self->next::method(@_);
843 if( $ret->admin ) {### If this is an admin, rebless for extra functions
844 $self->ensure_class_loaded( $admin_class );
845 bless $ret, $admin_class;
851 print "I am a regular user.\n";
858 package My::Schema::Result::User::Admin;
862 use base qw/My::Schema::Result::User/;
864 # This line is important
865 __PACKAGE__->table('users');
869 print "I am an admin.\n";
875 print "I am doing admin stuff\n";
887 my $user_data = { email => 'someguy@place.com',
891 my $admin_data = { email => 'someadmin@adminplace.com',
895 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
897 $schema->resultset('User')->create( $user_data );
898 $schema->resultset('User')->create( $admin_data );
900 ### Now we search for them
901 my $user = $schema->resultset('User')->single( $user_data );
902 my $admin = $schema->resultset('User')->single( $admin_data );
904 print ref $user, "\n";
905 print ref $admin, "\n";
907 print $user->password , "\n"; # pass1
908 print $admin->password , "\n";# pass2; inherited from User
909 print $user->hello , "\n";# I am a regular user.
910 print $admin->hello, "\n";# I am an admin.
912 ### The statement below will NOT print
913 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
914 ### The statement below will print
915 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
917 =head2 Skip row object creation for faster results
919 DBIx::Class is not built for speed, it's built for convenience and
920 ease of use, but sometimes you just need to get the data, and skip the
923 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
925 my $rs = $schema->resultset('CD');
927 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
929 my $hash_ref = $rs->find(1);
933 Beware, changing the Result class using
934 L<DBIx::Class::ResultSet/result_class> will replace any existing class
935 completely including any special components loaded using
936 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
938 =head2 Get raw data for blindingly fast results
940 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
941 above is not fast enough for you, you can use a DBIx::Class to return values
942 exactly as they come out of the database with none of the convenience methods
945 This is used like so:
947 my $cursor = $rs->cursor
948 while (my @vals = $cursor->next) {
949 # use $val[0..n] here
952 You will need to map the array offsets to particular columns (you can
953 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
955 =head1 RESULTSET OPERATIONS
957 =head2 Getting Schema from a ResultSet
959 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
961 $rs->result_source->schema
963 =head2 Getting Columns Of Data
967 If you want to find the sum of a particular column there are several
968 ways, the obvious one is to use search:
970 my $rs = $schema->resultset('Items')->search(
973 select => [ { sum => 'Cost' } ],
974 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
977 my $tc = $rs->first->get_column('total_cost');
979 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
980 returned when you ask the C<ResultSet> for a column using
983 my $cost = $schema->resultset('Items')->get_column('Cost');
986 With this you can also do:
988 my $minvalue = $cost->min;
989 my $maxvalue = $cost->max;
991 Or just iterate through the values of this column only:
993 while ( my $c = $cost->next ) {
997 foreach my $c ($cost->all) {
1001 C<ResultSetColumn> only has a limited number of built-in functions. If
1002 you need one that it doesn't have, then you can use the C<func> method
1005 my $avg = $cost->func('AVERAGE');
1007 This will cause the following SQL statement to be run:
1009 SELECT AVERAGE(Cost) FROM Items me
1011 Which will of course only work if your database supports this function.
1012 See L<DBIx::Class::ResultSetColumn> for more documentation.
1014 =head2 Creating a result set from a set of rows
1016 Sometimes you have a (set of) row objects that you want to put into a
1017 resultset without the need to hit the DB again. You can do that by using the
1018 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1020 my @uploadable_groups;
1021 while (my $group = $groups->next) {
1022 if ($group->can_upload($self)) {
1023 push @uploadable_groups, $group;
1026 my $new_rs = $self->result_source->resultset;
1027 $new_rs->set_cache(\@uploadable_groups);
1031 =head1 USING RELATIONSHIPS
1033 =head2 Create a new row in a related table
1035 my $author = $book->create_related('author', { name => 'Fred'});
1037 =head2 Search in a related table
1039 Only searches for books named 'Titanic' by the author in $author.
1041 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1043 =head2 Delete data in a related table
1045 Deletes only the book named Titanic by the author in $author.
1047 $author->delete_related('books', { name => 'Titanic' });
1049 =head2 Ordering a relationship result set
1051 If you always want a relation to be ordered, you can specify this when you
1052 create the relationship.
1054 To order C<< $book->pages >> by descending page_number, create the relation
1057 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
1059 =head2 Filtering a relationship result set
1061 If you want to get a filtered result set, you can just add add to $attr as follows:
1063 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1065 =head2 Many-to-many relationships
1067 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1070 use base 'DBIx::Class';
1071 __PACKAGE__->load_components('Core');
1072 __PACKAGE__->table('user');
1073 __PACKAGE__->add_columns(qw/id name/);
1074 __PACKAGE__->set_primary_key('id');
1075 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1076 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1078 package My::UserAddress;
1079 use base 'DBIx::Class';
1080 __PACKAGE__->load_components('Core');
1081 __PACKAGE__->table('user_address');
1082 __PACKAGE__->add_columns(qw/user address/);
1083 __PACKAGE__->set_primary_key(qw/user address/);
1084 __PACKAGE__->belongs_to('user' => 'My::User');
1085 __PACKAGE__->belongs_to('address' => 'My::Address');
1087 package My::Address;
1088 use base 'DBIx::Class';
1089 __PACKAGE__->load_components('Core');
1090 __PACKAGE__->table('address');
1091 __PACKAGE__->add_columns(qw/id street town area_code country/);
1092 __PACKAGE__->set_primary_key('id');
1093 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1094 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1096 $rs = $user->addresses(); # get all addresses for a user
1097 $rs = $address->users(); # get all users for an address
1099 =head2 Relationships across DB schemas
1101 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1102 is easy as long as the schemas themselves are all accessible via the same DBI
1103 connection. In most cases, this means that they are on the same database host
1104 as each other and your connecting database user has the proper permissions to them.
1106 To accomplish this one only needs to specify the DB schema name in the table
1107 declaration, like so...
1109 package MyDatabase::Main::Artist;
1110 use base qw/DBIx::Class/;
1111 __PACKAGE__->load_components(qw/PK::Auto Core/);
1113 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1115 __PACKAGE__->add_columns(qw/ artist_id name /);
1116 __PACKAGE__->set_primary_key('artist_id');
1117 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1121 Whatever string you specify there will be used to build the "FROM" clause in SQL
1124 The big drawback to this is you now have DB schema names hardcoded in your
1125 class files. This becomes especially troublesome if you have multiple instances
1126 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1127 the DB schemas are named based on the environment (e.g. database1_dev).
1129 However, one can dynamically "map" to the proper DB schema by overriding the
1130 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1131 building a renaming facility, like so:
1133 package MyDatabase::Schema;
1136 extends 'DBIx::Class::Schema';
1138 around connection => sub {
1139 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1141 my $postfix = delete $attr->{schema_name_postfix};
1146 $self->append_db_name($postfix);
1150 sub append_db_name {
1151 my ( $self, $postfix ) = @_;
1155 { $_->name =~ /^\w+\./mx }
1157 { $self->source($_) }
1160 foreach my $source (@sources_with_db) {
1161 my $name = $source->name;
1162 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1164 $source->name($name);
1170 By overridding the L<connection|DBIx::Class::Schama/connection>
1171 method and extracting a custom option from the provided \%attr hashref one can
1172 then simply iterate over all the Schema's ResultSources, renaming them as
1175 To use this facility, simply add or modify the \%attr hashref that is passed to
1176 L<connection|DBIx::Class::Schama/connect>, as follows:
1179 = MyDatabase::Schema->connect(
1184 schema_name_postfix => '_dev'
1185 # ... Other options as desired ...
1188 Obviously, one could accomplish even more advanced mapping via a hash map or a
1193 As of version 0.04001, there is improved transaction support in
1194 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1195 example of the recommended way to use it:
1197 my $genus = $schema->resultset('Genus')->find(12);
1199 my $coderef2 = sub {
1204 my $coderef1 = sub {
1205 $genus->add_to_species({ name => 'troglodyte' });
1208 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1209 return $genus->species;
1214 $rs = $schema->txn_do($coderef1);
1217 if ($@) { # Transaction failed
1218 die "the sky is falling!" #
1219 if ($@ =~ /Rollback failed/); # Rollback failed
1221 deal_with_failed_transaction();
1224 Nested transactions will work as expected. That is, only the outermost
1225 transaction will actually issue a commit to the $dbh, and a rollback
1226 at any level of any transaction will cause the entire nested
1227 transaction to fail. Support for savepoints and for true nested
1228 transactions (for databases that support them) will hopefully be added
1233 =head2 Creating Schemas From An Existing Database
1235 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1236 L<DBIx::Class::Schema> and associated sources by examining the database.
1238 The recommend way of achieving this is to use the
1239 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1241 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1242 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1244 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1245 source definitions for all the tables found in the C<foo> database.
1247 =head2 Creating DDL SQL
1249 The following functionality requires you to have L<SQL::Translator>
1250 (also known as "SQL Fairy") installed.
1252 To create a set of database-specific .sql files for the above schema:
1254 my $schema = My::Schema->connect($dsn);
1255 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1260 By default this will create schema files in the current directory, for
1261 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1263 To create a new database using the schema:
1265 my $schema = My::Schema->connect($dsn);
1266 $schema->deploy({ add_drop_tables => 1});
1268 To import created .sql files using the mysql client:
1270 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1272 To create C<ALTER TABLE> conversion scripts to update a database to a
1273 newer version of your schema at a later point, first set a new
1274 C<$VERSION> in your Schema file, then:
1276 my $schema = My::Schema->connect($dsn);
1277 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1283 This will produce new database-specific .sql files for the new version
1284 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1285 requires that the files for 0.1 as created above are available in the
1286 given directory to diff against.
1288 =head2 Select from dual
1290 Dummy tables are needed by some databases to allow calling functions
1291 or expressions that aren't based on table content, for examples of how
1292 this applies to various database types, see:
1293 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1295 Note: If you're using Oracles dual table don't B<ever> do anything
1296 other than a select, if you CRUD on your dual table you *will* break
1299 Make a table class as you would for any other table
1301 package MyAppDB::Dual;
1304 use base 'DBIx::Class';
1305 __PACKAGE__->load_components("Core");
1306 __PACKAGE__->table("Dual");
1307 __PACKAGE__->add_columns(
1309 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1312 Once you've loaded your table class select from it using C<select>
1313 and C<as> instead of C<columns>
1315 my $rs = $schema->resultset('Dual')->search(undef,
1316 { select => [ 'sydate' ],
1321 All you have to do now is be careful how you access your resultset, the below
1322 will not work because there is no column called 'now' in the Dual table class
1324 while (my $dual = $rs->next) {
1325 print $dual->now."\n";
1327 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1329 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1330 your Dual class for whatever you wanted to select from dual, but that's just
1331 silly, instead use C<get_column>
1333 while (my $dual = $rs->next) {
1334 print $dual->get_column('now')."\n";
1339 my $cursor = $rs->cursor;
1340 while (my @vals = $cursor->next) {
1341 print $vals[0]."\n";
1344 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1345 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1346 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1347 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1348 L<SQL::Translator> to not create table dual:
1351 add_drop_table => 1,
1352 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1354 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1356 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1358 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1359 while ( my $dual = $rs->next ) {
1360 print $dual->{now}."\n";
1363 Here are some example C<select> conditions to illustrate the different syntax
1364 you could use for doing stuff like
1365 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1367 # get a sequence value
1368 select => [ 'A_SEQ.nextval' ],
1370 # get create table sql
1371 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1373 # get a random num between 0 and 100
1374 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1377 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1380 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1382 # which day of the week were you born on?
1383 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1385 # select 16 rows from dual
1386 select => [ "'hello'" ],
1388 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1392 =head2 Adding Indexes And Functions To Your SQL
1394 Often you will want indexes on columns on your table to speed up searching. To
1395 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1396 class (refer to the advanced
1397 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1398 to share a hook between multiple sources):
1400 package My::Schema::Result::Artist;
1402 __PACKAGE__->table('artist');
1403 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1405 sub sqlt_deploy_hook {
1406 my ($self, $sqlt_table) = @_;
1408 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1413 Sometimes you might want to change the index depending on the type of the
1414 database for which SQL is being generated:
1416 my ($db_type = $sqlt_table->schema->translator->producer_type)
1417 =~ s/^SQL::Translator::Producer:://;
1419 You can also add hooks to the schema level to stop certain tables being
1426 sub sqlt_deploy_hook {
1427 my ($self, $sqlt_schema) = @_;
1429 $sqlt_schema->drop_table('table_name');
1432 You could also add views, procedures or triggers to the output using
1433 L<SQL::Translator::Schema/add_view>,
1434 L<SQL::Translator::Schema/add_procedure> or
1435 L<SQL::Translator::Schema/add_trigger>.
1438 =head2 Schema versioning
1440 The following example shows simplistically how you might use DBIx::Class to
1441 deploy versioned schemas to your customers. The basic process is as follows:
1447 Create a DBIx::Class schema
1459 Modify schema to change functionality
1463 Deploy update to customers
1467 B<Create a DBIx::Class schema>
1469 This can either be done manually, or generated from an existing database as
1470 described under L</Creating Schemas From An Existing Database>
1474 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1476 B<Deploy to customers>
1478 There are several ways you could deploy your schema. These are probably
1479 beyond the scope of this recipe, but might include:
1485 Require customer to apply manually using their RDBMS.
1489 Package along with your app, making database dump/schema update/tests
1490 all part of your install.
1494 B<Modify the schema to change functionality>
1496 As your application evolves, it may be necessary to modify your schema
1497 to change functionality. Once the changes are made to your schema in
1498 DBIx::Class, export the modified schema and the conversion scripts as
1499 in L</Creating DDL SQL>.
1501 B<Deploy update to customers>
1503 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1504 Schema class. This will add a new table to your database called
1505 C<dbix_class_schema_vesion> which will keep track of which version is installed
1506 and warn if the user trys to run a newer schema version than the
1507 database thinks it has.
1509 Alternatively, you can send the conversion sql scripts to your
1512 =head2 Setting quoting for the generated SQL.
1514 If the database contains column names with spaces and/or reserved words, they
1515 need to be quoted in the SQL queries. This is done using:
1517 __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
1518 __PACKAGE__->storage->sql_maker->name_sep('.');
1520 The first sets the quote characters. Either a pair of matching
1521 brackets, or a C<"> or C<'>:
1523 __PACKAGE__->storage->sql_maker->quote_char('"');
1525 Check the documentation of your database for the correct quote
1526 characters to use. C<name_sep> needs to be set to allow the SQL
1527 generator to put the quotes the correct place.
1529 In most cases you should set these as part of the arguments passed to
1530 L<DBIx::Class::Schema/connect>:
1532 my $schema = My::Schema->connect(
1542 =head2 Setting limit dialect for SQL::Abstract::Limit
1544 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1545 the remote SQL server by looking at the database handle. This is a
1546 common problem when using the DBD::JDBC, since the DBD-driver only
1547 know that in has a Java-driver available, not which JDBC driver the
1548 Java component has loaded. This specifically sets the limit_dialect
1549 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1552 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1554 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1555 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1557 The limit dialect can also be set at connect time by specifying a
1558 C<limit_dialect> key in the final hash as shown above.
1560 =head2 Working with PostgreSQL array types
1562 You can also assign values to PostgreSQL array columns by passing array
1563 references in the C<\%columns> (C<\%vals>) hashref of the
1564 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1567 $resultset->create({
1568 numbers => [1, 2, 3]
1573 numbers => [1, 2, 3]
1580 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1581 methods) you cannot directly use array references (since this is interpreted as
1582 a list of values to be C<OR>ed), but you can use the following syntax to force
1583 passing them as bind values:
1587 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1591 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1592 placeholders and bind values (subqueries)> for more explanation. Note that
1593 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1594 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1595 arrayrefs together with the column name, like this: C<< [column_name => value]
1598 =head1 BOOTSTRAPPING/MIGRATING
1600 =head2 Easy migration from class-based to schema-based setup
1602 You want to start using the schema-based approach to L<DBIx::Class>
1603 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1604 of existing classes that you don't want to move by hand. Try this nifty script
1608 use SQL::Translator;
1610 my $schema = MyDB->schema_instance;
1612 my $translator = SQL::Translator->new(
1613 debug => $debug || 0,
1614 trace => $trace || 0,
1615 no_comments => $no_comments || 0,
1616 show_warnings => $show_warnings || 0,
1617 add_drop_table => $add_drop_table || 0,
1618 validate => $validate || 0,
1620 'DBIx::Schema' => $schema,
1623 'prefix' => 'My::Schema',
1627 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1628 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1630 my $output = $translator->translate(@args) or die
1631 "Error: " . $translator->error;
1635 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1636 namespace, which is currently left as an exercise for the reader.
1638 =head1 OVERLOADING METHODS
1640 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1641 method calls, useful for things like default values and triggers. You have to
1642 use calls to C<next::method> to overload methods. More information on using
1643 L<Class::C3> with L<DBIx::Class> can be found in
1644 L<DBIx::Class::Manual::Component>.
1646 =head2 Setting default values for a row
1648 It's as simple as overriding the C<new> method. Note the use of
1652 my ( $class, $attrs ) = @_;
1654 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1656 my $new = $class->next::method($attrs);
1661 For more information about C<next::method>, look in the L<Class::C3>
1662 documentation. See also L<DBIx::Class::Manual::Component> for more
1663 ways to write your own base classes to do this.
1665 People looking for ways to do "triggers" with DBIx::Class are probably
1666 just looking for this.
1668 =head2 Changing one field whenever another changes
1670 For example, say that you have three columns, C<id>, C<number>, and
1671 C<squared>. You would like to make changes to C<number> and have
1672 C<squared> be automagically set to the value of C<number> squared.
1673 You can accomplish this by overriding C<store_column>:
1676 my ( $self, $name, $value ) = @_;
1677 if ($name eq 'number') {
1678 $self->squared($value * $value);
1680 $self->next::method($name, $value);
1683 Note that the hard work is done by the call to C<next::method>, which
1684 redispatches your call to store_column in the superclass(es).
1686 =head2 Automatically creating related objects
1688 You might have a class C<Artist> which has many C<CD>s. Further, you
1689 want to create a C<CD> object every time you insert an C<Artist> object.
1690 You can accomplish this by overriding C<insert> on your objects:
1693 my ( $self, @args ) = @_;
1694 $self->next::method(@args);
1695 $self->cds->new({})->fill_from_artist($self)->insert;
1699 where C<fill_from_artist> is a method you specify in C<CD> which sets
1700 values in C<CD> based on the data in the C<Artist> object you pass in.
1702 =head2 Wrapping/overloading a column accessor
1706 Say you have a table "Camera" and want to associate a description
1707 with each camera. For most cameras, you'll be able to generate the description from
1708 the other columns. However, in a few special cases you may want to associate a
1709 custom description with a camera.
1713 In your database schema, define a description field in the "Camera" table that
1714 can contain text and null values.
1716 In DBIC, we'll overload the column accessor to provide a sane default if no
1717 custom description is defined. The accessor will either return or generate the
1718 description, depending on whether the field is null or not.
1720 First, in your "Camera" schema class, define the description field as follows:
1722 __PACKAGE__->add_columns(description => { accessor => '_description' });
1724 Next, we'll define the accessor-wrapper subroutine:
1729 # If there is an update to the column, we'll let the original accessor
1731 return $self->_description(@_) if @_;
1733 # Fetch the column value.
1734 my $description = $self->_description;
1736 # If there's something in the description field, then just return that.
1737 return $description if defined $description && length $descripton;
1739 # Otherwise, generate a description.
1740 return $self->generate_description;
1743 =head1 DEBUGGING AND PROFILING
1745 =head2 DBIx::Class objects with Data::Dumper
1747 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1748 be hard to find the pertinent data in all the data it can generate.
1749 Specifically, if one naively tries to use it like so,
1753 my $cd = $schema->resultset('CD')->find(1);
1756 several pages worth of data from the CD object's schema and result source will
1757 be dumped to the screen. Since usually one is only interested in a few column
1758 values of the object, this is not very helpful.
1760 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1761 it. Simply define a hook that L<Data::Dumper> will call on the object before
1762 dumping it. For example,
1769 result_source => undef,
1777 local $Data::Dumper::Freezer = '_dumper_hook';
1779 my $cd = $schema->resultset('CD')->find(1);
1781 # dumps $cd without its ResultSource
1783 If the structure of your schema is such that there is a common base class for
1784 all your table classes, simply put a method similar to C<_dumper_hook> in the
1785 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1786 will automagically clean up your data before printing it. See
1787 L<Data::Dumper/EXAMPLES> for more information.
1791 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1792 executed as well as notifications of query completion and transaction
1793 begin/commit. If you'd like to profile the SQL you can subclass the
1794 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1797 package My::Profiler;
1800 use base 'DBIx::Class::Storage::Statistics';
1802 use Time::HiRes qw(time);
1811 $self->print("Executing $sql: ".join(', ', @params)."\n");
1820 my $elapsed = sprintf("%0.4f", time() - $start);
1821 $self->print("Execution took $elapsed seconds.\n");
1827 You can then install that class as the debugging object:
1829 __PACKAGE__->storage->debugobj(new My::Profiler());
1830 __PACKAGE__->storage->debug(1);
1832 A more complicated example might involve storing each execution of SQL in an
1840 my $elapsed = time() - $start;
1841 push(@{ $calls{$sql} }, {
1847 You could then create average, high and low execution times for an SQL
1848 statement and dig down to see if certain parameters cause aberrant behavior.
1849 You might want to check out L<DBIx::Class::QueryLog> as well.
1851 =head1 STARTUP SPEED
1853 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1854 as the ORM loads all the relevant classes. This section examines
1855 techniques for reducing the startup delay.
1857 These tips are are listed in order of decreasing effectiveness - so the
1858 first tip, if applicable, should have the greatest effect on your
1861 =head2 Statically Define Your Schema
1864 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1865 classes dynamically based on the database schema then there will be a
1866 significant startup delay.
1868 For production use a statically defined schema (which can be generated
1869 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1870 the database schema once - see
1871 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1872 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1873 details on creating static schemas from a database).
1875 =head2 Move Common Startup into a Base Class
1877 Typically L<DBIx::Class> result classes start off with
1879 use base qw/DBIx::Class/;
1880 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1882 If this preamble is moved into a common base class:-
1886 use base qw/DBIx::Class/;
1887 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1890 and each result class then uses this as a base:-
1892 use base qw/MyDBICbase/;
1894 then the load_components is only performed once, which can result in a
1895 considerable startup speedup for schemas with many classes.
1897 =head2 Explicitly List Schema Result Classes
1899 The schema class will normally contain
1901 __PACKAGE__->load_classes();
1903 to load the result classes. This will use L<Module::Find|Module::Find>
1904 to find and load the appropriate modules. Explicitly defining the
1905 classes you wish to load will remove the overhead of
1906 L<Module::Find|Module::Find> and the related directory operations:
1908 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1910 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1911 syntax to load the appropriate classes there is not a direct alternative
1912 avoiding L<Module::Find|Module::Find>.
1916 =head2 Cached statements
1918 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
1919 This is normally a good idea, but if too many statements are cached, the database may use too much
1920 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
1921 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
1923 # print all currently cached prepared statements
1924 print for keys %{$schema->storage->dbh->{CachedKids}};
1925 # get a count of currently cached prepared statements
1926 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
1928 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
1931 my $kids = $schema->storage->dbh->{CachedKids};
1932 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
1934 But what you probably want is to expire unused statements and not those that are used frequently.
1935 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
1939 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
1940 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },