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/;
118 __PACKAGE__->load_components('Core');
119 __PACKAGE__->table_class('DBIx::Class::ResultSource::View');
121 # ->table, ->add_columns, etc.
123 # do not attempt to deploy() this view
124 __PACKAGE__->result_source_instance->is_virtual(1);
126 __PACKAGE__->result_source_instance->view_definition(q[
127 SELECT u.* FROM user u
128 INNER JOIN user_friends f ON u.id = f.user_id
129 WHERE f.friend_user_id = ?
131 SELECT u.* FROM user u
132 INNER JOIN user_friends f ON u.id = f.friend_user_id
136 Next, you can execute your complex query using bind parameters like this:
138 my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {},
140 bind => [ 12345, 12345 ]
144 ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
145 that you cannot modify the rows it contains, ie. cannot call L</update>,
146 L</delete>, ... on it).
148 Note that you cannot have bind parameters unless is_virtual is set to true.
154 If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
155 method for custom SQL execution, you are highly encouraged to update your code
156 to use a virtual view as above. If you do not want to change your code, and just
157 want to suppress the deprecation warning when you call
158 L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
159 C<deploy> will exclude this "table":
161 sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
165 =head2 Using specific columns
167 When you only want specific columns from a table, you can use
168 C<columns> to specify which ones you need. This is useful to avoid
169 loading columns with large amounts of data that you aren't about to
172 my $rs = $schema->resultset('Artist')->search(
175 columns => [qw/ name /]
180 # SELECT artist.name FROM artist
182 This is a shortcut for C<select> and C<as>, see below. C<columns>
183 cannot be used together with C<select> and C<as>.
185 =head2 Using database functions or stored procedures
187 The combination of C<select> and C<as> can be used to return the result of a
188 database function or stored procedure as a column value. You use C<select> to
189 specify the source for your column value (e.g. a column name, function, or
190 stored procedure name). You then use C<as> to set the column name you will use
191 to access the returned value:
193 my $rs = $schema->resultset('Artist')->search(
196 select => [ 'name', { LENGTH => 'name' } ],
197 as => [qw/ name name_length /],
202 # SELECT name name, LENGTH( name )
205 Note that the C<as> attribute B<has absolutely nothing to do> with the sql
206 syntax C< SELECT foo AS bar > (see the documentation in
207 L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
208 generated SQL via the C<-as> field attribute as follows:
210 my $rs = $schema->resultset('Artist')->search(
215 '+select' => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ],
216 '+as' => [qw/num_cds/],
217 order_by => { -desc => 'amount_of_cds' },
222 # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds
223 # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
224 # GROUP BY me.artistid, me.name, me.rank, me.charfield
225 # ORDER BY amount_of_cds DESC
228 If your alias exists as a column in your base class (i.e. it was added with
229 L<add_columns|DBIx::Class::ResultSource/add_columns>), you just access it as
230 normal. Our C<Artist> class has a C<name> column, so we just use the C<name>
233 my $artist = $rs->first();
234 my $name = $artist->name();
236 If on the other hand the alias does not correspond to an existing column, you
237 have to fetch the value using the C<get_column> accessor:
239 my $name_length = $artist->get_column('name_length');
241 If you don't like using C<get_column>, you can always create an accessor for
242 any of your aliases using either of these:
244 # Define accessor manually:
245 sub name_length { shift->get_column('name_length'); }
247 # Or use DBIx::Class::AccessorGroup:
248 __PACKAGE__->mk_group_accessors('column' => 'name_length');
250 =head2 SELECT DISTINCT with multiple columns
252 my $rs = $schema->resultset('Artist')->search(
255 columns => [ qw/artist_id name rank/ ],
260 my $rs = $schema->resultset('Artist')->search(
263 columns => [ qw/artist_id name rank/ ],
264 group_by => [ qw/artist_id name rank/ ],
269 # SELECT me.artist_id, me.name, me.rank
271 # GROUP BY artist_id, name, rank
273 =head2 SELECT COUNT(DISTINCT colname)
275 my $rs = $schema->resultset('Artist')->search(
278 columns => [ qw/name/ ],
283 my $rs = $schema->resultset('Artist')->search(
286 columns => [ qw/name/ ],
287 group_by => [ qw/name/ ],
291 my $count = $rs->count;
294 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
296 =head2 Grouping results
298 L<DBIx::Class> supports C<GROUP BY> as follows:
300 my $rs = $schema->resultset('Artist')->search(
304 select => [ 'name', { count => 'cds.id' } ],
305 as => [qw/ name cd_count /],
306 group_by => [qw/ name /]
311 # SELECT name, COUNT( cd.id ) FROM artist
312 # LEFT JOIN cd ON artist.id = cd.artist
315 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
316 are in any way unsure about the use of the attributes above (C< join
317 >, C< select >, C< as > and C< group_by >).
319 =head2 Subqueries (EXPERIMENTAL)
321 You can write subqueries relatively easily in DBIC.
323 my $inside_rs = $schema->resultset('Artist')->search({
324 name => [ 'Billy Joel', 'Brittany Spears' ],
327 my $rs = $schema->resultset('CD')->search({
328 artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
331 The usual operators ( =, !=, IN, NOT IN, etc) are supported.
333 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
334 The following will B<not> work:
336 my $rs = $schema->resultset('CD')->search({
337 artist_id => $inside_rs->get_column('id')->as_query,
342 Subqueries are supported in the where clause (first hashref), and in the
343 from, select, and +select attributes.
345 =head3 Correlated subqueries
347 my $cdrs = $schema->resultset('CD');
348 my $rs = $cdrs->search({
350 '=' => $cdrs->search(
351 { artist_id => { '=' => \'me.artist_id' } },
353 )->get_column('year')->max_rs->as_query,
357 That creates the following SQL:
359 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
362 SELECT MAX(inner.year)
364 WHERE artist_id = me.artist_id
369 Please note that subqueries are considered an experimental feature.
371 =head2 Predefined searches
373 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
374 and defining often used searches as methods:
376 package My::DBIC::ResultSet::CD;
379 use base 'DBIx::Class::ResultSet';
381 sub search_cds_ordered {
384 return $self->search(
386 { order_by => 'name DESC' },
392 To use your resultset, first tell DBIx::Class to create an instance of it
393 for you, in your My::DBIC::Schema::CD class:
395 # class definition as normal
396 __PACKAGE__->load_components(qw/ Core /);
397 __PACKAGE__->table('cd');
399 # tell DBIC to use the custom ResultSet class
400 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
402 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
404 Then call your new method in your code:
406 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
408 =head2 Using SQL functions on the left hand side of a comparison
410 Using SQL functions on the left hand side of a comparison is generally
411 not a good idea since it requires a scan of the entire table. However,
412 it can be accomplished with C<DBIx::Class> when necessary.
414 If you do not have quoting on, simply include the function in your search
415 specification as you would any column:
417 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
419 With quoting on, or for a more portable solution, use the C<where>
422 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
426 (When the bind args ordering bug is fixed, this technique will be better
427 and can replace the one above.)
429 With quoting on, or for a more portable solution, use the C<where> and
433 where => \'YEAR(date_of_birth) = ?',
439 =head1 JOINS AND PREFETCHING
441 =head2 Using joins and prefetch
443 You can use the C<join> attribute to allow searching on, or sorting your
444 results by, one or more columns in a related table.
446 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
448 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
450 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
452 my $rs = $schema->resultset('CD')->search(
454 'artists.name' => 'Bob Marley'
457 join => 'artists', # join the artist table
462 # SELECT cd.* FROM cd
463 # JOIN artist ON cd.artist = artist.id
464 # WHERE artist.name = 'Bob Marley'
466 In that example both the join, and the condition use the relationship name rather than the table name
467 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
469 If required, you can now sort on any column in the related tables by including
470 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
472 my $rs = $schema->resultset('CD')->search(
474 'artists.name' => 'Bob Marley'
478 order_by => [qw/ artists.name /]
483 # SELECT cd.* FROM cd
484 # JOIN artist ON cd.artist = artist.id
485 # WHERE artist.name = 'Bob Marley'
486 # ORDER BY artist.name
488 Note that the C<join> attribute should only be used when you need to search or
489 sort using columns in a related table. Joining related tables when you only
490 need columns from the main table will make performance worse!
492 Now let's say you want to display a list of CDs, each with the name of the
493 artist. The following will work fine:
495 while (my $cd = $rs->next) {
496 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
499 There is a problem however. We have searched both the C<cd> and C<artist> tables
500 in our main query, but we have only returned data from the C<cd> table. To get
501 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
504 SELECT artist.* FROM artist WHERE artist.id = ?
506 A statement like the one above will run for each and every CD returned by our
507 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
510 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
511 This allows you to fetch results from related tables in advance:
513 my $rs = $schema->resultset('CD')->search(
515 'artists.name' => 'Bob Marley'
519 order_by => [qw/ artists.name /],
520 prefetch => 'artists' # return artist data too!
524 # Equivalent SQL (note SELECT from both "cd" and "artist"):
525 # SELECT cd.*, artist.* FROM cd
526 # JOIN artist ON cd.artist = artist.id
527 # WHERE artist.name = 'Bob Marley'
528 # ORDER BY artist.name
530 The code to print the CD list remains the same:
532 while (my $cd = $rs->next) {
533 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
536 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
537 so no additional SQL statements are executed. You now have a much more
540 Also note that C<prefetch> should only be used when you know you will
541 definitely use data from a related table. Pre-fetching related tables when you
542 only need columns from the main table will make performance worse!
544 =head2 Multiple joins
546 In the examples above, the C<join> attribute was a scalar. If you
547 pass an array reference instead, you can join to multiple tables. In
548 this example, we want to limit the search further, using
551 # Relationships defined elsewhere:
552 # CD->belongs_to('artist' => 'Artist');
553 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
554 my $rs = $schema->resultset('CD')->search(
556 'artist.name' => 'Bob Marley'
557 'liner_notes.notes' => { 'like', '%some text%' },
560 join => [qw/ artist liner_notes /],
561 order_by => [qw/ artist.name /],
566 # SELECT cd.*, artist.*, liner_notes.* FROM cd
567 # JOIN artist ON cd.artist = artist.id
568 # JOIN liner_notes ON cd.id = liner_notes.cd
569 # WHERE artist.name = 'Bob Marley'
570 # ORDER BY artist.name
572 =head2 Multi-step joins
574 Sometimes you want to join more than one relationship deep. In this example,
575 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
576 contain a specific string:
578 # Relationships defined elsewhere:
579 # Artist->has_many('cds' => 'CD', 'artist');
580 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
582 my $rs = $schema->resultset('Artist')->search(
584 'liner_notes.notes' => { 'like', '%some text%' },
588 'cds' => 'liner_notes'
594 # SELECT artist.* FROM artist
595 # LEFT JOIN cd ON artist.id = cd.artist
596 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
597 # WHERE liner_notes.notes LIKE '%some text%'
599 Joins can be nested to an arbitrary level. So if we decide later that we
600 want to reduce the number of Artists returned based on who wrote the liner
603 # Relationship defined elsewhere:
604 # LinerNotes->belongs_to('author' => 'Person');
606 my $rs = $schema->resultset('Artist')->search(
608 'liner_notes.notes' => { 'like', '%some text%' },
609 'author.name' => 'A. Writer'
614 'liner_notes' => 'author'
621 # SELECT artist.* FROM artist
622 # LEFT JOIN cd ON artist.id = cd.artist
623 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
624 # LEFT JOIN author ON author.id = liner_notes.author
625 # WHERE liner_notes.notes LIKE '%some text%'
626 # AND author.name = 'A. Writer'
628 =head2 Multi-step and multiple joins
630 With various combinations of array and hash references, you can join
631 tables in any combination you desire. For example, to join Artist to
632 CD and Concert, and join CD to LinerNotes:
634 # Relationships defined elsewhere:
635 # Artist->has_many('concerts' => 'Concert', 'artist');
637 my $rs = $schema->resultset('Artist')->search(
650 # SELECT artist.* FROM artist
651 # LEFT JOIN cd ON artist.id = cd.artist
652 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
653 # LEFT JOIN concert ON artist.id = concert.artist
655 =head2 Multi-step prefetch
657 C<prefetch> can be nested more than one relationship
658 deep using the same syntax as a multi-step join:
660 my $rs = $schema->resultset('Tag')->search(
670 # SELECT tag.*, cd.*, artist.* FROM tag
671 # JOIN cd ON tag.cd = cd.id
672 # JOIN artist ON cd.artist = artist.id
674 Now accessing our C<cd> and C<artist> relationships does not need additional
677 my $tag = $rs->first;
678 print $tag->cd->artist->name;
680 =head1 ROW-LEVEL OPERATIONS
682 =head2 Retrieving a row object's Schema
684 It is possible to get a Schema object from a row object like so:
686 my $schema = $cd->result_source->schema;
687 # use the schema as normal:
688 my $artist_rs = $schema->resultset('Artist');
690 This can be useful when you don't want to pass around a Schema object to every
693 =head2 Getting the value of the primary key for the last database insert
695 AKA getting last_insert_id
697 Thanks to the core component PK::Auto, this is straightforward:
699 my $foo = $rs->create(\%blah);
701 my $id = $foo->id; # foo->my_primary_key_field will also work.
703 If you are not using autoincrementing primary keys, this will probably
704 not work, but then you already know the value of the last primary key anyway.
706 =head2 Stringification
708 Employ the standard stringification technique by using the L<overload>
711 To make an object stringify itself as a single column, use something
712 like this (replace C<name> with the column/method of your choice):
714 use overload '""' => sub { shift->name}, fallback => 1;
716 For more complex stringification, you can use an anonymous subroutine:
718 use overload '""' => sub { $_[0]->name . ", " .
719 $_[0]->address }, fallback => 1;
721 =head3 Stringification Example
723 Suppose we have two tables: C<Product> and C<Category>. The table
726 Product(id, Description, category)
727 Category(id, Description)
729 C<category> is a foreign key into the Category table.
731 If you have a Product object C<$obj> and write something like
735 things will not work as expected.
737 To obtain, for example, the category description, you should add this
738 method to the class defining the Category table:
740 use overload "" => sub {
743 return $self->Description;
746 =head2 Want to know if find_or_create found or created a row?
748 Just use C<find_or_new> instead, then check C<in_storage>:
750 my $obj = $rs->find_or_new({ blah => 'blarg' });
751 unless ($obj->in_storage) {
753 # do whatever else you wanted if it was a new row
756 =head2 Static sub-classing DBIx::Class result classes
758 AKA adding additional relationships/methods/etc. to a model for a
759 specific usage of the (shared) model.
763 package My::App::Schema;
765 use base DBIx::Class::Schema;
767 # load subclassed classes from My::App::Schema::Result/ResultSet
768 __PACKAGE__->load_namespaces;
770 # load classes from shared model
772 'My::Shared::Model::Result' => [qw/
779 B<Result-Subclass definition>
781 package My::App::Schema::Result::Baz;
785 use base My::Shared::Model::Result::Baz;
787 # WARNING: Make sure you call table() again in your subclass,
788 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
789 # and the class name is not correctly registered as a source
790 __PACKAGE__->table('baz');
792 sub additional_method {
793 return "I'm an additional method only needed by this app";
798 =head2 Dynamic Sub-classing DBIx::Class proxy classes
800 AKA multi-class object inflation from one table
802 L<DBIx::Class> classes are proxy classes, therefore some different
803 techniques need to be employed for more than basic subclassing. In
804 this example we have a single user table that carries a boolean bit
805 for admin. We would like like to give the admin users
806 objects (L<DBIx::Class::Row>) the same methods as a regular user but
807 also special admin only methods. It doesn't make sense to create two
808 seperate proxy-class files for this. We would be copying all the user
809 methods into the Admin class. There is a cleaner way to accomplish
812 Overriding the C<inflate_result> method within the User proxy-class
813 gives us the effect we want. This method is called by
814 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
815 grab the object being returned, inspect the values we are looking for,
816 bless it if it's an admin object, and then return it. See the example
823 use base qw/DBIx::Class::Schema/;
825 __PACKAGE__->load_namespaces;
830 B<Proxy-Class definitions>
832 package My::Schema::Result::User;
836 use base qw/DBIx::Class/;
838 ### Define what our admin class is, for ensure_class_loaded()
839 my $admin_class = __PACKAGE__ . '::Admin';
841 __PACKAGE__->load_components(qw/Core/);
843 __PACKAGE__->table('users');
845 __PACKAGE__->add_columns(qw/user_id email password
846 firstname lastname active
849 __PACKAGE__->set_primary_key('user_id');
853 my $ret = $self->next::method(@_);
854 if( $ret->admin ) {### If this is an admin, rebless for extra functions
855 $self->ensure_class_loaded( $admin_class );
856 bless $ret, $admin_class;
862 print "I am a regular user.\n";
869 package My::Schema::Result::User::Admin;
873 use base qw/My::Schema::Result::User/;
875 # This line is important
876 __PACKAGE__->table('users');
880 print "I am an admin.\n";
886 print "I am doing admin stuff\n";
898 my $user_data = { email => 'someguy@place.com',
902 my $admin_data = { email => 'someadmin@adminplace.com',
906 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
908 $schema->resultset('User')->create( $user_data );
909 $schema->resultset('User')->create( $admin_data );
911 ### Now we search for them
912 my $user = $schema->resultset('User')->single( $user_data );
913 my $admin = $schema->resultset('User')->single( $admin_data );
915 print ref $user, "\n";
916 print ref $admin, "\n";
918 print $user->password , "\n"; # pass1
919 print $admin->password , "\n";# pass2; inherited from User
920 print $user->hello , "\n";# I am a regular user.
921 print $admin->hello, "\n";# I am an admin.
923 ### The statement below will NOT print
924 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
925 ### The statement below will print
926 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
928 =head2 Skip row object creation for faster results
930 DBIx::Class is not built for speed, it's built for convenience and
931 ease of use, but sometimes you just need to get the data, and skip the
934 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
936 my $rs = $schema->resultset('CD');
938 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
940 my $hash_ref = $rs->find(1);
944 Beware, changing the Result class using
945 L<DBIx::Class::ResultSet/result_class> will replace any existing class
946 completely including any special components loaded using
947 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
949 =head2 Get raw data for blindingly fast results
951 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
952 above is not fast enough for you, you can use a DBIx::Class to return values
953 exactly as they come out of the database with none of the convenience methods
956 This is used like so:
958 my $cursor = $rs->cursor
959 while (my @vals = $cursor->next) {
960 # use $val[0..n] here
963 You will need to map the array offsets to particular columns (you can
964 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
966 =head1 RESULTSET OPERATIONS
968 =head2 Getting Schema from a ResultSet
970 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
972 $rs->result_source->schema
974 =head2 Getting Columns Of Data
978 If you want to find the sum of a particular column there are several
979 ways, the obvious one is to use search:
981 my $rs = $schema->resultset('Items')->search(
984 select => [ { sum => 'Cost' } ],
985 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
988 my $tc = $rs->first->get_column('total_cost');
990 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
991 returned when you ask the C<ResultSet> for a column using
994 my $cost = $schema->resultset('Items')->get_column('Cost');
997 With this you can also do:
999 my $minvalue = $cost->min;
1000 my $maxvalue = $cost->max;
1002 Or just iterate through the values of this column only:
1004 while ( my $c = $cost->next ) {
1008 foreach my $c ($cost->all) {
1012 C<ResultSetColumn> only has a limited number of built-in functions. If
1013 you need one that it doesn't have, then you can use the C<func> method
1016 my $avg = $cost->func('AVERAGE');
1018 This will cause the following SQL statement to be run:
1020 SELECT AVERAGE(Cost) FROM Items me
1022 Which will of course only work if your database supports this function.
1023 See L<DBIx::Class::ResultSetColumn> for more documentation.
1025 =head2 Creating a result set from a set of rows
1027 Sometimes you have a (set of) row objects that you want to put into a
1028 resultset without the need to hit the DB again. You can do that by using the
1029 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1031 my @uploadable_groups;
1032 while (my $group = $groups->next) {
1033 if ($group->can_upload($self)) {
1034 push @uploadable_groups, $group;
1037 my $new_rs = $self->result_source->resultset;
1038 $new_rs->set_cache(\@uploadable_groups);
1042 =head1 USING RELATIONSHIPS
1044 =head2 Create a new row in a related table
1046 my $author = $book->create_related('author', { name => 'Fred'});
1048 =head2 Search in a related table
1050 Only searches for books named 'Titanic' by the author in $author.
1052 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1054 =head2 Delete data in a related table
1056 Deletes only the book named Titanic by the author in $author.
1058 $author->delete_related('books', { name => 'Titanic' });
1060 =head2 Ordering a relationship result set
1062 If you always want a relation to be ordered, you can specify this when you
1063 create the relationship.
1065 To order C<< $book->pages >> by descending page_number, create the relation
1068 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
1070 =head2 Filtering a relationship result set
1072 If you want to get a filtered result set, you can just add add to $attr as follows:
1074 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1076 =head2 Many-to-many relationships
1078 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1081 use base 'DBIx::Class';
1082 __PACKAGE__->load_components('Core');
1083 __PACKAGE__->table('user');
1084 __PACKAGE__->add_columns(qw/id name/);
1085 __PACKAGE__->set_primary_key('id');
1086 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1087 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1089 package My::UserAddress;
1090 use base 'DBIx::Class';
1091 __PACKAGE__->load_components('Core');
1092 __PACKAGE__->table('user_address');
1093 __PACKAGE__->add_columns(qw/user address/);
1094 __PACKAGE__->set_primary_key(qw/user address/);
1095 __PACKAGE__->belongs_to('user' => 'My::User');
1096 __PACKAGE__->belongs_to('address' => 'My::Address');
1098 package My::Address;
1099 use base 'DBIx::Class';
1100 __PACKAGE__->load_components('Core');
1101 __PACKAGE__->table('address');
1102 __PACKAGE__->add_columns(qw/id street town area_code country/);
1103 __PACKAGE__->set_primary_key('id');
1104 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1105 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1107 $rs = $user->addresses(); # get all addresses for a user
1108 $rs = $address->users(); # get all users for an address
1110 =head2 Relationships across DB schemas
1112 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1113 is easy as long as the schemas themselves are all accessible via the same DBI
1114 connection. In most cases, this means that they are on the same database host
1115 as each other and your connecting database user has the proper permissions to them.
1117 To accomplish this one only needs to specify the DB schema name in the table
1118 declaration, like so...
1120 package MyDatabase::Main::Artist;
1121 use base qw/DBIx::Class/;
1122 __PACKAGE__->load_components(qw/PK::Auto Core/);
1124 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1126 __PACKAGE__->add_columns(qw/ artist_id name /);
1127 __PACKAGE__->set_primary_key('artist_id');
1128 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1132 Whatever string you specify there will be used to build the "FROM" clause in SQL
1135 The big drawback to this is you now have DB schema names hardcoded in your
1136 class files. This becomes especially troublesome if you have multiple instances
1137 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1138 the DB schemas are named based on the environment (e.g. database1_dev).
1140 However, one can dynamically "map" to the proper DB schema by overriding the
1141 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1142 building a renaming facility, like so:
1144 package MyDatabase::Schema;
1147 extends 'DBIx::Class::Schema';
1149 around connection => sub {
1150 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1152 my $postfix = delete $attr->{schema_name_postfix};
1157 $self->append_db_name($postfix);
1161 sub append_db_name {
1162 my ( $self, $postfix ) = @_;
1166 { $_->name =~ /^\w+\./mx }
1168 { $self->source($_) }
1171 foreach my $source (@sources_with_db) {
1172 my $name = $source->name;
1173 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1175 $source->name($name);
1181 By overridding the L<connection|DBIx::Class::Schama/connection>
1182 method and extracting a custom option from the provided \%attr hashref one can
1183 then simply iterate over all the Schema's ResultSources, renaming them as
1186 To use this facility, simply add or modify the \%attr hashref that is passed to
1187 L<connection|DBIx::Class::Schama/connect>, as follows:
1190 = MyDatabase::Schema->connect(
1195 schema_name_postfix => '_dev'
1196 # ... Other options as desired ...
1199 Obviously, one could accomplish even more advanced mapping via a hash map or a
1204 As of version 0.04001, there is improved transaction support in
1205 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1206 example of the recommended way to use it:
1208 my $genus = $schema->resultset('Genus')->find(12);
1210 my $coderef2 = sub {
1215 my $coderef1 = sub {
1216 $genus->add_to_species({ name => 'troglodyte' });
1219 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1220 return $genus->species;
1225 $rs = $schema->txn_do($coderef1);
1228 if ($@) { # Transaction failed
1229 die "the sky is falling!" #
1230 if ($@ =~ /Rollback failed/); # Rollback failed
1232 deal_with_failed_transaction();
1235 Nested transactions will work as expected. That is, only the outermost
1236 transaction will actually issue a commit to the $dbh, and a rollback
1237 at any level of any transaction will cause the entire nested
1238 transaction to fail. Support for savepoints and for true nested
1239 transactions (for databases that support them) will hopefully be added
1244 =head2 Creating Schemas From An Existing Database
1246 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1247 L<DBIx::Class::Schema> and associated sources by examining the database.
1249 The recommend way of achieving this is to use the
1250 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1252 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1253 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1255 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1256 source definitions for all the tables found in the C<foo> database.
1258 =head2 Creating DDL SQL
1260 The following functionality requires you to have L<SQL::Translator>
1261 (also known as "SQL Fairy") installed.
1263 To create a set of database-specific .sql files for the above schema:
1265 my $schema = My::Schema->connect($dsn);
1266 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1271 By default this will create schema files in the current directory, for
1272 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1274 To create a new database using the schema:
1276 my $schema = My::Schema->connect($dsn);
1277 $schema->deploy({ add_drop_tables => 1});
1279 To import created .sql files using the mysql client:
1281 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1283 To create C<ALTER TABLE> conversion scripts to update a database to a
1284 newer version of your schema at a later point, first set a new
1285 C<$VERSION> in your Schema file, then:
1287 my $schema = My::Schema->connect($dsn);
1288 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1294 This will produce new database-specific .sql files for the new version
1295 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1296 requires that the files for 0.1 as created above are available in the
1297 given directory to diff against.
1299 =head2 Select from dual
1301 Dummy tables are needed by some databases to allow calling functions
1302 or expressions that aren't based on table content, for examples of how
1303 this applies to various database types, see:
1304 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1306 Note: If you're using Oracles dual table don't B<ever> do anything
1307 other than a select, if you CRUD on your dual table you *will* break
1310 Make a table class as you would for any other table
1312 package MyAppDB::Dual;
1315 use base 'DBIx::Class';
1316 __PACKAGE__->load_components("Core");
1317 __PACKAGE__->table("Dual");
1318 __PACKAGE__->add_columns(
1320 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1323 Once you've loaded your table class select from it using C<select>
1324 and C<as> instead of C<columns>
1326 my $rs = $schema->resultset('Dual')->search(undef,
1327 { select => [ 'sydate' ],
1332 All you have to do now is be careful how you access your resultset, the below
1333 will not work because there is no column called 'now' in the Dual table class
1335 while (my $dual = $rs->next) {
1336 print $dual->now."\n";
1338 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1340 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1341 your Dual class for whatever you wanted to select from dual, but that's just
1342 silly, instead use C<get_column>
1344 while (my $dual = $rs->next) {
1345 print $dual->get_column('now')."\n";
1350 my $cursor = $rs->cursor;
1351 while (my @vals = $cursor->next) {
1352 print $vals[0]."\n";
1355 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1356 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1357 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1358 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1359 L<SQL::Translator> to not create table dual:
1362 add_drop_table => 1,
1363 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1365 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1367 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1369 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1370 while ( my $dual = $rs->next ) {
1371 print $dual->{now}."\n";
1374 Here are some example C<select> conditions to illustrate the different syntax
1375 you could use for doing stuff like
1376 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1378 # get a sequence value
1379 select => [ 'A_SEQ.nextval' ],
1381 # get create table sql
1382 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1384 # get a random num between 0 and 100
1385 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1388 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1391 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1393 # which day of the week were you born on?
1394 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1396 # select 16 rows from dual
1397 select => [ "'hello'" ],
1399 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1403 =head2 Adding Indexes And Functions To Your SQL
1405 Often you will want indexes on columns on your table to speed up searching. To
1406 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1407 class (refer to the advanced
1408 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1409 to share a hook between multiple sources):
1411 package My::Schema::Result::Artist;
1413 __PACKAGE__->table('artist');
1414 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1416 sub sqlt_deploy_hook {
1417 my ($self, $sqlt_table) = @_;
1419 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1424 Sometimes you might want to change the index depending on the type of the
1425 database for which SQL is being generated:
1427 my ($db_type = $sqlt_table->schema->translator->producer_type)
1428 =~ s/^SQL::Translator::Producer:://;
1430 You can also add hooks to the schema level to stop certain tables being
1437 sub sqlt_deploy_hook {
1438 my ($self, $sqlt_schema) = @_;
1440 $sqlt_schema->drop_table('table_name');
1443 You could also add views, procedures or triggers to the output using
1444 L<SQL::Translator::Schema/add_view>,
1445 L<SQL::Translator::Schema/add_procedure> or
1446 L<SQL::Translator::Schema/add_trigger>.
1449 =head2 Schema versioning
1451 The following example shows simplistically how you might use DBIx::Class to
1452 deploy versioned schemas to your customers. The basic process is as follows:
1458 Create a DBIx::Class schema
1470 Modify schema to change functionality
1474 Deploy update to customers
1478 B<Create a DBIx::Class schema>
1480 This can either be done manually, or generated from an existing database as
1481 described under L</Creating Schemas From An Existing Database>
1485 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1487 B<Deploy to customers>
1489 There are several ways you could deploy your schema. These are probably
1490 beyond the scope of this recipe, but might include:
1496 Require customer to apply manually using their RDBMS.
1500 Package along with your app, making database dump/schema update/tests
1501 all part of your install.
1505 B<Modify the schema to change functionality>
1507 As your application evolves, it may be necessary to modify your schema
1508 to change functionality. Once the changes are made to your schema in
1509 DBIx::Class, export the modified schema and the conversion scripts as
1510 in L</Creating DDL SQL>.
1512 B<Deploy update to customers>
1514 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1515 Schema class. This will add a new table to your database called
1516 C<dbix_class_schema_vesion> which will keep track of which version is installed
1517 and warn if the user trys to run a newer schema version than the
1518 database thinks it has.
1520 Alternatively, you can send the conversion sql scripts to your
1523 =head2 Setting quoting for the generated SQL
1525 If the database contains column names with spaces and/or reserved words, they
1526 need to be quoted in the SQL queries. This is done using:
1528 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1529 $schema->storage->sql_maker->name_sep('.');
1531 The first sets the quote characters. Either a pair of matching
1532 brackets, or a C<"> or C<'>:
1534 $schema->storage->sql_maker->quote_char('"');
1536 Check the documentation of your database for the correct quote
1537 characters to use. C<name_sep> needs to be set to allow the SQL
1538 generator to put the quotes the correct place.
1540 In most cases you should set these as part of the arguments passed to
1541 L<DBIx::Class::Schema/connect>:
1543 my $schema = My::Schema->connect(
1553 In some cases, quoting will be required for all users of a schema. To enforce
1554 this, you can also overload the C<connection> method for your schema class:
1558 my $rv = $self->next::method( @_ );
1559 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1560 $rv->storage->sql_maker->name_sep('.');
1564 =head2 Setting limit dialect for SQL::Abstract::Limit
1566 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1567 the remote SQL server by looking at the database handle. This is a
1568 common problem when using the DBD::JDBC, since the DBD-driver only
1569 know that in has a Java-driver available, not which JDBC driver the
1570 Java component has loaded. This specifically sets the limit_dialect
1571 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1574 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1576 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1577 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1579 The limit dialect can also be set at connect time by specifying a
1580 C<limit_dialect> key in the final hash as shown above.
1582 =head2 Working with PostgreSQL array types
1584 You can also assign values to PostgreSQL array columns by passing array
1585 references in the C<\%columns> (C<\%vals>) hashref of the
1586 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1589 $resultset->create({
1590 numbers => [1, 2, 3]
1595 numbers => [1, 2, 3]
1602 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1603 methods) you cannot directly use array references (since this is interpreted as
1604 a list of values to be C<OR>ed), but you can use the following syntax to force
1605 passing them as bind values:
1609 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1613 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1614 placeholders and bind values (subqueries)> for more explanation. Note that
1615 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1616 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1617 arrayrefs together with the column name, like this: C<< [column_name => value]
1620 =head1 BOOTSTRAPPING/MIGRATING
1622 =head2 Easy migration from class-based to schema-based setup
1624 You want to start using the schema-based approach to L<DBIx::Class>
1625 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1626 of existing classes that you don't want to move by hand. Try this nifty script
1630 use SQL::Translator;
1632 my $schema = MyDB->schema_instance;
1634 my $translator = SQL::Translator->new(
1635 debug => $debug || 0,
1636 trace => $trace || 0,
1637 no_comments => $no_comments || 0,
1638 show_warnings => $show_warnings || 0,
1639 add_drop_table => $add_drop_table || 0,
1640 validate => $validate || 0,
1642 'DBIx::Schema' => $schema,
1645 'prefix' => 'My::Schema',
1649 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1650 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1652 my $output = $translator->translate(@args) or die
1653 "Error: " . $translator->error;
1657 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1658 namespace, which is currently left as an exercise for the reader.
1660 =head1 OVERLOADING METHODS
1662 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1663 method calls, useful for things like default values and triggers. You have to
1664 use calls to C<next::method> to overload methods. More information on using
1665 L<Class::C3> with L<DBIx::Class> can be found in
1666 L<DBIx::Class::Manual::Component>.
1668 =head2 Setting default values for a row
1670 It's as simple as overriding the C<new> method. Note the use of
1674 my ( $class, $attrs ) = @_;
1676 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1678 my $new = $class->next::method($attrs);
1683 For more information about C<next::method>, look in the L<Class::C3>
1684 documentation. See also L<DBIx::Class::Manual::Component> for more
1685 ways to write your own base classes to do this.
1687 People looking for ways to do "triggers" with DBIx::Class are probably
1688 just looking for this.
1690 =head2 Changing one field whenever another changes
1692 For example, say that you have three columns, C<id>, C<number>, and
1693 C<squared>. You would like to make changes to C<number> and have
1694 C<squared> be automagically set to the value of C<number> squared.
1695 You can accomplish this by overriding C<store_column>:
1698 my ( $self, $name, $value ) = @_;
1699 if ($name eq 'number') {
1700 $self->squared($value * $value);
1702 $self->next::method($name, $value);
1705 Note that the hard work is done by the call to C<next::method>, which
1706 redispatches your call to store_column in the superclass(es).
1708 =head2 Automatically creating related objects
1710 You might have a class C<Artist> which has many C<CD>s. Further, you
1711 want to create a C<CD> object every time you insert an C<Artist> object.
1712 You can accomplish this by overriding C<insert> on your objects:
1715 my ( $self, @args ) = @_;
1716 $self->next::method(@args);
1717 $self->cds->new({})->fill_from_artist($self)->insert;
1721 where C<fill_from_artist> is a method you specify in C<CD> which sets
1722 values in C<CD> based on the data in the C<Artist> object you pass in.
1724 =head2 Wrapping/overloading a column accessor
1728 Say you have a table "Camera" and want to associate a description
1729 with each camera. For most cameras, you'll be able to generate the description from
1730 the other columns. However, in a few special cases you may want to associate a
1731 custom description with a camera.
1735 In your database schema, define a description field in the "Camera" table that
1736 can contain text and null values.
1738 In DBIC, we'll overload the column accessor to provide a sane default if no
1739 custom description is defined. The accessor will either return or generate the
1740 description, depending on whether the field is null or not.
1742 First, in your "Camera" schema class, define the description field as follows:
1744 __PACKAGE__->add_columns(description => { accessor => '_description' });
1746 Next, we'll define the accessor-wrapper subroutine:
1751 # If there is an update to the column, we'll let the original accessor
1753 return $self->_description(@_) if @_;
1755 # Fetch the column value.
1756 my $description = $self->_description;
1758 # If there's something in the description field, then just return that.
1759 return $description if defined $description && length $descripton;
1761 # Otherwise, generate a description.
1762 return $self->generate_description;
1765 =head1 DEBUGGING AND PROFILING
1767 =head2 DBIx::Class objects with Data::Dumper
1769 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1770 be hard to find the pertinent data in all the data it can generate.
1771 Specifically, if one naively tries to use it like so,
1775 my $cd = $schema->resultset('CD')->find(1);
1778 several pages worth of data from the CD object's schema and result source will
1779 be dumped to the screen. Since usually one is only interested in a few column
1780 values of the object, this is not very helpful.
1782 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1783 it. Simply define a hook that L<Data::Dumper> will call on the object before
1784 dumping it. For example,
1791 result_source => undef,
1799 local $Data::Dumper::Freezer = '_dumper_hook';
1801 my $cd = $schema->resultset('CD')->find(1);
1803 # dumps $cd without its ResultSource
1805 If the structure of your schema is such that there is a common base class for
1806 all your table classes, simply put a method similar to C<_dumper_hook> in the
1807 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1808 will automagically clean up your data before printing it. See
1809 L<Data::Dumper/EXAMPLES> for more information.
1813 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1814 executed as well as notifications of query completion and transaction
1815 begin/commit. If you'd like to profile the SQL you can subclass the
1816 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1819 package My::Profiler;
1822 use base 'DBIx::Class::Storage::Statistics';
1824 use Time::HiRes qw(time);
1833 $self->print("Executing $sql: ".join(', ', @params)."\n");
1842 my $elapsed = sprintf("%0.4f", time() - $start);
1843 $self->print("Execution took $elapsed seconds.\n");
1849 You can then install that class as the debugging object:
1851 __PACKAGE__->storage->debugobj(new My::Profiler());
1852 __PACKAGE__->storage->debug(1);
1854 A more complicated example might involve storing each execution of SQL in an
1862 my $elapsed = time() - $start;
1863 push(@{ $calls{$sql} }, {
1869 You could then create average, high and low execution times for an SQL
1870 statement and dig down to see if certain parameters cause aberrant behavior.
1871 You might want to check out L<DBIx::Class::QueryLog> as well.
1873 =head1 STARTUP SPEED
1875 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1876 as the ORM loads all the relevant classes. This section examines
1877 techniques for reducing the startup delay.
1879 These tips are are listed in order of decreasing effectiveness - so the
1880 first tip, if applicable, should have the greatest effect on your
1883 =head2 Statically Define Your Schema
1886 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1887 classes dynamically based on the database schema then there will be a
1888 significant startup delay.
1890 For production use a statically defined schema (which can be generated
1891 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1892 the database schema once - see
1893 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1894 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1895 details on creating static schemas from a database).
1897 =head2 Move Common Startup into a Base Class
1899 Typically L<DBIx::Class> result classes start off with
1901 use base qw/DBIx::Class/;
1902 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1904 If this preamble is moved into a common base class:-
1908 use base qw/DBIx::Class/;
1909 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1912 and each result class then uses this as a base:-
1914 use base qw/MyDBICbase/;
1916 then the load_components is only performed once, which can result in a
1917 considerable startup speedup for schemas with many classes.
1919 =head2 Explicitly List Schema Result Classes
1921 The schema class will normally contain
1923 __PACKAGE__->load_classes();
1925 to load the result classes. This will use L<Module::Find|Module::Find>
1926 to find and load the appropriate modules. Explicitly defining the
1927 classes you wish to load will remove the overhead of
1928 L<Module::Find|Module::Find> and the related directory operations:
1930 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1932 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1933 syntax to load the appropriate classes there is not a direct alternative
1934 avoiding L<Module::Find|Module::Find>.
1938 =head2 Cached statements
1940 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
1941 This is normally a good idea, but if too many statements are cached, the database may use too much
1942 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
1943 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
1945 # print all currently cached prepared statements
1946 print for keys %{$schema->storage->dbh->{CachedKids}};
1947 # get a count of currently cached prepared statements
1948 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
1950 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
1953 my $kids = $schema->storage->dbh->{CachedKids};
1954 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
1956 But what you probably want is to expire unused statements and not those that are used frequently.
1957 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
1961 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
1962 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },