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 '%Lamb%' AND title LIKE '%Fear of Fours%'
42 Other queries might require slightly more complex logic:
44 my @albums = $schema->resultset('Album')->search({
47 artist => { 'like', '%Smashing Pumpkins%' },
48 title => 'Siamese Dream',
50 artist => 'Starchildren',
54 This results in the following C<WHERE> clause:
56 WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
57 OR artist = 'Starchildren'
59 For more information on generating complex queries, see
60 L<SQL::Abstract/WHERE CLAUSES>.
62 =head2 Retrieve one and only one row from a resultset
64 Sometimes you need only the first "top" row of a resultset. While this
65 can be easily done with L<< $rs->first|DBIx::Class::ResultSet/first
66 >>, it is suboptimal, as a full blown cursor for the resultset will be
67 created and then immediately destroyed after fetching the first row
68 object. L<< $rs->single|DBIx::Class::ResultSet/single >> is designed
69 specifically for this case - it will grab the first returned result
70 without even instantiating a cursor.
72 Before replacing all your calls to C<first()> with C<single()> please observe the
79 While single() takes a search condition just like search() does, it does
80 _not_ accept search attributes. However one can always chain a single() to
83 my $top_cd = $cd_rs->search({}, { order_by => 'rating' })->single;
88 Since single() is the engine behind find(), it is designed to fetch a
89 single row per database query. Thus a warning will be issued when the
90 underlying SELECT returns more than one row. Sometimes however this usage
91 is valid: i.e. we have an arbitrary number of cd's but only one of them is
92 at the top of the charts at any given time. If you know what you are doing,
93 you can silence the warning by explicitly limiting the resultset size:
95 my $top_cd = $cd_rs->search ({}, { order_by => 'rating', rows => 1 })->single;
99 =head2 Arbitrary SQL through a custom ResultSource
101 Sometimes you have to run arbitrary SQL because your query is too complex
102 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
103 be optimized for your database in a special way, but you still want to
104 get the results as a L<DBIx::Class::ResultSet>.
106 This is accomplished by defining a
107 L<ResultSource::View|DBIx::Class::ResultSource::View> for your query,
108 almost like you would define a regular ResultSource.
110 package My::Schema::Result::UserFriendsComplex;
113 use base qw/DBIx::Class/;
115 __PACKAGE__->load_components('Core');
116 __PACKAGE__->table_class('DBIx::Class::ResultSource::View');
118 # ->table, ->add_columns, etc.
120 # do not attempt to deploy() this view
121 __PACKAGE__->result_source_instance->is_virtual(1);
123 __PACKAGE__->result_source_instance->view_definition(q[
124 SELECT u.* FROM user u
125 INNER JOIN user_friends f ON u.id = f.user_id
126 WHERE f.friend_user_id = ?
128 SELECT u.* FROM user u
129 INNER JOIN user_friends f ON u.id = f.friend_user_id
133 Next, you can execute your complex query using bind parameters like this:
135 my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {},
137 bind => [ 12345, 12345 ]
141 ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
142 that you cannot modify the rows it contains, ie. cannot call L</update>,
143 L</delete>, ... on it).
145 Note that you cannot have bind parameters unless is_virtual is set to true.
151 If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
152 method for custom SQL execution, you are highly encouraged to update your code
153 to use a virtual view as above. If you do not want to change your code, and just
154 want to suppress the deprecation warning when you call
155 L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
156 C<deploy> will exclude this "table":
158 sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
162 =head2 Using specific columns
164 When you only want specific columns from a table, you can use
165 C<columns> to specify which ones you need. This is useful to avoid
166 loading columns with large amounts of data that you aren't about to
169 my $rs = $schema->resultset('Artist')->search(
172 columns => [qw/ name /]
177 # SELECT artist.name FROM artist
179 This is a shortcut for C<select> and C<as>, see below. C<columns>
180 cannot be used together with C<select> and C<as>.
182 =head2 Using database functions or stored procedures
184 The combination of C<select> and C<as> can be used to return the result of a
185 database function or stored procedure as a column value. You use C<select> to
186 specify the source for your column value (e.g. a column name, function, or
187 stored procedure name). You then use C<as> to set the column name you will use
188 to access the returned value:
190 my $rs = $schema->resultset('Artist')->search(
193 select => [ 'name', { LENGTH => 'name' } ],
194 as => [qw/ name name_length /],
199 # SELECT name name, LENGTH( name )
202 Note that the C<as> attribute B<has absolutely nothing to do> with the sql
203 syntax C< SELECT foo AS bar > (see the documentation in
204 L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
205 generated SQL via the C<-as> field attribute as follows:
207 my $rs = $schema->resultset('Artist')->search(
212 '+select' => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ],
213 '+as' => [qw/num_cds/],
214 order_by => { -desc => 'amount_of_cds' },
219 # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds
220 # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
221 # GROUP BY me.artistid, me.name, me.rank, me.charfield
222 # ORDER BY amount_of_cds DESC
225 If your alias exists as a column in your base class (i.e. it was added with
226 L<add_columns|DBIx::Class::ResultSource/add_columns>), you just access it as
227 normal. Our C<Artist> class has a C<name> column, so we just use the C<name>
230 my $artist = $rs->first();
231 my $name = $artist->name();
233 If on the other hand the alias does not correspond to an existing column, you
234 have to fetch the value using the C<get_column> accessor:
236 my $name_length = $artist->get_column('name_length');
238 If you don't like using C<get_column>, you can always create an accessor for
239 any of your aliases using either of these:
241 # Define accessor manually:
242 sub name_length { shift->get_column('name_length'); }
244 # Or use DBIx::Class::AccessorGroup:
245 __PACKAGE__->mk_group_accessors('column' => 'name_length');
247 =head2 SELECT DISTINCT with multiple columns
249 my $rs = $schema->resultset('Artist')->search(
252 columns => [ qw/artist_id name rank/ ],
257 my $rs = $schema->resultset('Artist')->search(
260 columns => [ qw/artist_id name rank/ ],
261 group_by => [ qw/artist_id name rank/ ],
266 # SELECT me.artist_id, me.name, me.rank
268 # GROUP BY artist_id, name, rank
270 =head2 SELECT COUNT(DISTINCT colname)
272 my $rs = $schema->resultset('Artist')->search(
275 columns => [ qw/name/ ],
280 my $rs = $schema->resultset('Artist')->search(
283 columns => [ qw/name/ ],
284 group_by => [ qw/name/ ],
288 my $count = $rs->count;
291 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
293 =head2 Grouping results
295 L<DBIx::Class> supports C<GROUP BY> as follows:
297 my $rs = $schema->resultset('Artist')->search(
301 select => [ 'name', { count => 'cds.id' } ],
302 as => [qw/ name cd_count /],
303 group_by => [qw/ name /]
308 # SELECT name, COUNT( cd.id ) FROM artist
309 # LEFT JOIN cd ON artist.id = cd.artist
312 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
313 are in any way unsure about the use of the attributes above (C< join
314 >, C< select >, C< as > and C< group_by >).
316 =head2 Subqueries (EXPERIMENTAL)
318 You can write subqueries relatively easily in DBIC.
320 my $inside_rs = $schema->resultset('Artist')->search({
321 name => [ 'Billy Joel', 'Brittany Spears' ],
324 my $rs = $schema->resultset('CD')->search({
325 artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
328 The usual operators ( =, !=, IN, NOT IN, etc) are supported.
330 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
331 The following will B<not> work:
333 my $rs = $schema->resultset('CD')->search({
334 artist_id => $inside_rs->get_column('id')->as_query,
339 Subqueries are supported in the where clause (first hashref), and in the
340 from, select, and +select attributes.
342 =head3 Correlated subqueries
344 my $cdrs = $schema->resultset('CD');
345 my $rs = $cdrs->search({
347 '=' => $cdrs->search(
348 { artist_id => { '=' => \'me.artist_id' } },
350 )->get_column('year')->max_rs->as_query,
354 That creates the following SQL:
356 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
359 SELECT MAX(inner.year)
361 WHERE artist_id = me.artist_id
366 Please note that subqueries are considered an experimental feature.
368 =head2 Predefined searches
370 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
371 and defining often used searches as methods:
373 package My::DBIC::ResultSet::CD;
376 use base 'DBIx::Class::ResultSet';
378 sub search_cds_ordered {
381 return $self->search(
383 { order_by => 'name DESC' },
389 To use your resultset, first tell DBIx::Class to create an instance of it
390 for you, in your My::DBIC::Schema::CD class:
392 # class definition as normal
393 __PACKAGE__->load_components(qw/ Core /);
394 __PACKAGE__->table('cd');
396 # tell DBIC to use the custom ResultSet class
397 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
399 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
401 Then call your new method in your code:
403 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
405 =head2 Using SQL functions on the left hand side of a comparison
407 Using SQL functions on the left hand side of a comparison is generally
408 not a good idea since it requires a scan of the entire table. However,
409 it can be accomplished with C<DBIx::Class> when necessary.
411 If you do not have quoting on, simply include the function in your search
412 specification as you would any column:
414 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
416 With quoting on, or for a more portable solution, use the C<where>
419 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
423 (When the bind args ordering bug is fixed, this technique will be better
424 and can replace the one above.)
426 With quoting on, or for a more portable solution, use the C<where> and
430 where => \'YEAR(date_of_birth) = ?',
436 =head1 JOINS AND PREFETCHING
438 =head2 Using joins and prefetch
440 You can use the C<join> attribute to allow searching on, or sorting your
441 results by, one or more columns in a related table.
443 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
445 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
447 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
449 my $rs = $schema->resultset('CD')->search(
451 'artists.name' => 'Bob Marley'
454 join => 'artists', # join the artist table
459 # SELECT cd.* FROM cd
460 # JOIN artist ON cd.artist = artist.id
461 # WHERE artist.name = 'Bob Marley'
463 In that example both the join, and the condition use the relationship name rather than the table name
464 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
466 If required, you can now sort on any column in the related tables by including
467 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
469 my $rs = $schema->resultset('CD')->search(
471 'artists.name' => 'Bob Marley'
475 order_by => [qw/ artists.name /]
480 # SELECT cd.* FROM cd
481 # JOIN artist ON cd.artist = artist.id
482 # WHERE artist.name = 'Bob Marley'
483 # ORDER BY artist.name
485 Note that the C<join> attribute should only be used when you need to search or
486 sort using columns in a related table. Joining related tables when you only
487 need columns from the main table will make performance worse!
489 Now let's say you want to display a list of CDs, each with the name of the
490 artist. The following will work fine:
492 while (my $cd = $rs->next) {
493 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
496 There is a problem however. We have searched both the C<cd> and C<artist> tables
497 in our main query, but we have only returned data from the C<cd> table. To get
498 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
501 SELECT artist.* FROM artist WHERE artist.id = ?
503 A statement like the one above will run for each and every CD returned by our
504 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
507 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
508 This allows you to fetch results from related tables in advance:
510 my $rs = $schema->resultset('CD')->search(
512 'artists.name' => 'Bob Marley'
516 order_by => [qw/ artists.name /],
517 prefetch => 'artists' # return artist data too!
521 # Equivalent SQL (note SELECT from both "cd" and "artist"):
522 # SELECT cd.*, artist.* FROM cd
523 # JOIN artist ON cd.artist = artist.id
524 # WHERE artist.name = 'Bob Marley'
525 # ORDER BY artist.name
527 The code to print the CD list remains the same:
529 while (my $cd = $rs->next) {
530 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
533 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
534 so no additional SQL statements are executed. You now have a much more
537 Also note that C<prefetch> should only be used when you know you will
538 definitely use data from a related table. Pre-fetching related tables when you
539 only need columns from the main table will make performance worse!
541 =head2 Multiple joins
543 In the examples above, the C<join> attribute was a scalar. If you
544 pass an array reference instead, you can join to multiple tables. In
545 this example, we want to limit the search further, using
548 # Relationships defined elsewhere:
549 # CD->belongs_to('artist' => 'Artist');
550 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
551 my $rs = $schema->resultset('CD')->search(
553 'artist.name' => 'Bob Marley'
554 'liner_notes.notes' => { 'like', '%some text%' },
557 join => [qw/ artist liner_notes /],
558 order_by => [qw/ artist.name /],
563 # SELECT cd.*, artist.*, liner_notes.* FROM cd
564 # JOIN artist ON cd.artist = artist.id
565 # JOIN liner_notes ON cd.id = liner_notes.cd
566 # WHERE artist.name = 'Bob Marley'
567 # ORDER BY artist.name
569 =head2 Multi-step joins
571 Sometimes you want to join more than one relationship deep. In this example,
572 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
573 contain a specific string:
575 # Relationships defined elsewhere:
576 # Artist->has_many('cds' => 'CD', 'artist');
577 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
579 my $rs = $schema->resultset('Artist')->search(
581 'liner_notes.notes' => { 'like', '%some text%' },
585 'cds' => 'liner_notes'
591 # SELECT artist.* FROM artist
592 # LEFT JOIN cd ON artist.id = cd.artist
593 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
594 # WHERE liner_notes.notes LIKE '%some text%'
596 Joins can be nested to an arbitrary level. So if we decide later that we
597 want to reduce the number of Artists returned based on who wrote the liner
600 # Relationship defined elsewhere:
601 # LinerNotes->belongs_to('author' => 'Person');
603 my $rs = $schema->resultset('Artist')->search(
605 'liner_notes.notes' => { 'like', '%some text%' },
606 'author.name' => 'A. Writer'
611 'liner_notes' => 'author'
618 # SELECT artist.* FROM artist
619 # LEFT JOIN cd ON artist.id = cd.artist
620 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
621 # LEFT JOIN author ON author.id = liner_notes.author
622 # WHERE liner_notes.notes LIKE '%some text%'
623 # AND author.name = 'A. Writer'
625 =head2 Multi-step and multiple joins
627 With various combinations of array and hash references, you can join
628 tables in any combination you desire. For example, to join Artist to
629 CD and Concert, and join CD to LinerNotes:
631 # Relationships defined elsewhere:
632 # Artist->has_many('concerts' => 'Concert', 'artist');
634 my $rs = $schema->resultset('Artist')->search(
647 # SELECT artist.* FROM artist
648 # LEFT JOIN cd ON artist.id = cd.artist
649 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
650 # LEFT JOIN concert ON artist.id = concert.artist
652 =head2 Multi-step prefetch
654 C<prefetch> can be nested more than one relationship
655 deep using the same syntax as a multi-step join:
657 my $rs = $schema->resultset('Tag')->search(
667 # SELECT tag.*, cd.*, artist.* FROM tag
668 # JOIN cd ON tag.cd = cd.id
669 # JOIN artist ON cd.artist = artist.id
671 Now accessing our C<cd> and C<artist> relationships does not need additional
674 my $tag = $rs->first;
675 print $tag->cd->artist->name;
677 =head1 ROW-LEVEL OPERATIONS
679 =head2 Retrieving a row object's Schema
681 It is possible to get a Schema object from a row object like so:
683 my $schema = $cd->result_source->schema;
684 # use the schema as normal:
685 my $artist_rs = $schema->resultset('Artist');
687 This can be useful when you don't want to pass around a Schema object to every
690 =head2 Getting the value of the primary key for the last database insert
692 AKA getting last_insert_id
694 Thanks to the core component PK::Auto, this is straightforward:
696 my $foo = $rs->create(\%blah);
698 my $id = $foo->id; # foo->my_primary_key_field will also work.
700 If you are not using autoincrementing primary keys, this will probably
701 not work, but then you already know the value of the last primary key anyway.
703 =head2 Stringification
705 Employ the standard stringification technique by using the L<overload>
708 To make an object stringify itself as a single column, use something
709 like this (replace C<name> with the column/method of your choice):
711 use overload '""' => sub { shift->name}, fallback => 1;
713 For more complex stringification, you can use an anonymous subroutine:
715 use overload '""' => sub { $_[0]->name . ", " .
716 $_[0]->address }, fallback => 1;
718 =head3 Stringification Example
720 Suppose we have two tables: C<Product> and C<Category>. The table
723 Product(id, Description, category)
724 Category(id, Description)
726 C<category> is a foreign key into the Category table.
728 If you have a Product object C<$obj> and write something like
732 things will not work as expected.
734 To obtain, for example, the category description, you should add this
735 method to the class defining the Category table:
737 use overload "" => sub {
740 return $self->Description;
743 =head2 Want to know if find_or_create found or created a row?
745 Just use C<find_or_new> instead, then check C<in_storage>:
747 my $obj = $rs->find_or_new({ blah => 'blarg' });
748 unless ($obj->in_storage) {
750 # do whatever else you wanted if it was a new row
753 =head2 Static sub-classing DBIx::Class result classes
755 AKA adding additional relationships/methods/etc. to a model for a
756 specific usage of the (shared) model.
760 package My::App::Schema;
762 use base DBIx::Class::Schema;
764 # load subclassed classes from My::App::Schema::Result/ResultSet
765 __PACKAGE__->load_namespaces;
767 # load classes from shared model
769 'My::Shared::Model::Result' => [qw/
776 B<Result-Subclass definition>
778 package My::App::Schema::Result::Baz;
782 use base My::Shared::Model::Result::Baz;
784 # WARNING: Make sure you call table() again in your subclass,
785 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
786 # and the class name is not correctly registered as a source
787 __PACKAGE__->table('baz');
789 sub additional_method {
790 return "I'm an additional method only needed by this app";
795 =head2 Dynamic Sub-classing DBIx::Class proxy classes
797 AKA multi-class object inflation from one table
799 L<DBIx::Class> classes are proxy classes, therefore some different
800 techniques need to be employed for more than basic subclassing. In
801 this example we have a single user table that carries a boolean bit
802 for admin. We would like like to give the admin users
803 objects (L<DBIx::Class::Row>) the same methods as a regular user but
804 also special admin only methods. It doesn't make sense to create two
805 seperate proxy-class files for this. We would be copying all the user
806 methods into the Admin class. There is a cleaner way to accomplish
809 Overriding the C<inflate_result> method within the User proxy-class
810 gives us the effect we want. This method is called by
811 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
812 grab the object being returned, inspect the values we are looking for,
813 bless it if it's an admin object, and then return it. See the example
820 use base qw/DBIx::Class::Schema/;
822 __PACKAGE__->load_namespaces;
827 B<Proxy-Class definitions>
829 package My::Schema::Result::User;
833 use base qw/DBIx::Class/;
835 ### Define what our admin class is, for ensure_class_loaded()
836 my $admin_class = __PACKAGE__ . '::Admin';
838 __PACKAGE__->load_components(qw/Core/);
840 __PACKAGE__->table('users');
842 __PACKAGE__->add_columns(qw/user_id email password
843 firstname lastname active
846 __PACKAGE__->set_primary_key('user_id');
850 my $ret = $self->next::method(@_);
851 if( $ret->admin ) {### If this is an admin, rebless for extra functions
852 $self->ensure_class_loaded( $admin_class );
853 bless $ret, $admin_class;
859 print "I am a regular user.\n";
866 package My::Schema::Result::User::Admin;
870 use base qw/My::Schema::Result::User/;
872 # This line is important
873 __PACKAGE__->table('users');
877 print "I am an admin.\n";
883 print "I am doing admin stuff\n";
895 my $user_data = { email => 'someguy@place.com',
899 my $admin_data = { email => 'someadmin@adminplace.com',
903 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
905 $schema->resultset('User')->create( $user_data );
906 $schema->resultset('User')->create( $admin_data );
908 ### Now we search for them
909 my $user = $schema->resultset('User')->single( $user_data );
910 my $admin = $schema->resultset('User')->single( $admin_data );
912 print ref $user, "\n";
913 print ref $admin, "\n";
915 print $user->password , "\n"; # pass1
916 print $admin->password , "\n";# pass2; inherited from User
917 print $user->hello , "\n";# I am a regular user.
918 print $admin->hello, "\n";# I am an admin.
920 ### The statement below will NOT print
921 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
922 ### The statement below will print
923 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
925 =head2 Skip row object creation for faster results
927 DBIx::Class is not built for speed, it's built for convenience and
928 ease of use, but sometimes you just need to get the data, and skip the
931 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
933 my $rs = $schema->resultset('CD');
935 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
937 my $hash_ref = $rs->find(1);
941 Beware, changing the Result class using
942 L<DBIx::Class::ResultSet/result_class> will replace any existing class
943 completely including any special components loaded using
944 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
946 =head2 Get raw data for blindingly fast results
948 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
949 above is not fast enough for you, you can use a DBIx::Class to return values
950 exactly as they come out of the database with none of the convenience methods
953 This is used like so:
955 my $cursor = $rs->cursor
956 while (my @vals = $cursor->next) {
957 # use $val[0..n] here
960 You will need to map the array offsets to particular columns (you can
961 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
963 =head1 RESULTSET OPERATIONS
965 =head2 Getting Schema from a ResultSet
967 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
969 $rs->result_source->schema
971 =head2 Getting Columns Of Data
975 If you want to find the sum of a particular column there are several
976 ways, the obvious one is to use search:
978 my $rs = $schema->resultset('Items')->search(
981 select => [ { sum => 'Cost' } ],
982 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
985 my $tc = $rs->first->get_column('total_cost');
987 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
988 returned when you ask the C<ResultSet> for a column using
991 my $cost = $schema->resultset('Items')->get_column('Cost');
994 With this you can also do:
996 my $minvalue = $cost->min;
997 my $maxvalue = $cost->max;
999 Or just iterate through the values of this column only:
1001 while ( my $c = $cost->next ) {
1005 foreach my $c ($cost->all) {
1009 C<ResultSetColumn> only has a limited number of built-in functions. If
1010 you need one that it doesn't have, then you can use the C<func> method
1013 my $avg = $cost->func('AVERAGE');
1015 This will cause the following SQL statement to be run:
1017 SELECT AVERAGE(Cost) FROM Items me
1019 Which will of course only work if your database supports this function.
1020 See L<DBIx::Class::ResultSetColumn> for more documentation.
1022 =head2 Creating a result set from a set of rows
1024 Sometimes you have a (set of) row objects that you want to put into a
1025 resultset without the need to hit the DB again. You can do that by using the
1026 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1028 my @uploadable_groups;
1029 while (my $group = $groups->next) {
1030 if ($group->can_upload($self)) {
1031 push @uploadable_groups, $group;
1034 my $new_rs = $self->result_source->resultset;
1035 $new_rs->set_cache(\@uploadable_groups);
1039 =head1 USING RELATIONSHIPS
1041 =head2 Create a new row in a related table
1043 my $author = $book->create_related('author', { name => 'Fred'});
1045 =head2 Search in a related table
1047 Only searches for books named 'Titanic' by the author in $author.
1049 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1051 =head2 Delete data in a related table
1053 Deletes only the book named Titanic by the author in $author.
1055 $author->delete_related('books', { name => 'Titanic' });
1057 =head2 Ordering a relationship result set
1059 If you always want a relation to be ordered, you can specify this when you
1060 create the relationship.
1062 To order C<< $book->pages >> by descending page_number, create the relation
1065 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
1067 =head2 Filtering a relationship result set
1069 If you want to get a filtered result set, you can just add add to $attr as follows:
1071 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1073 =head2 Many-to-many relationships
1075 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1078 use base 'DBIx::Class';
1079 __PACKAGE__->load_components('Core');
1080 __PACKAGE__->table('user');
1081 __PACKAGE__->add_columns(qw/id name/);
1082 __PACKAGE__->set_primary_key('id');
1083 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1084 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1086 package My::UserAddress;
1087 use base 'DBIx::Class';
1088 __PACKAGE__->load_components('Core');
1089 __PACKAGE__->table('user_address');
1090 __PACKAGE__->add_columns(qw/user address/);
1091 __PACKAGE__->set_primary_key(qw/user address/);
1092 __PACKAGE__->belongs_to('user' => 'My::User');
1093 __PACKAGE__->belongs_to('address' => 'My::Address');
1095 package My::Address;
1096 use base 'DBIx::Class';
1097 __PACKAGE__->load_components('Core');
1098 __PACKAGE__->table('address');
1099 __PACKAGE__->add_columns(qw/id street town area_code country/);
1100 __PACKAGE__->set_primary_key('id');
1101 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1102 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1104 $rs = $user->addresses(); # get all addresses for a user
1105 $rs = $address->users(); # get all users for an address
1107 =head2 Relationships across DB schemas
1109 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1110 is easy as long as the schemas themselves are all accessible via the same DBI
1111 connection. In most cases, this means that they are on the same database host
1112 as each other and your connecting database user has the proper permissions to them.
1114 To accomplish this one only needs to specify the DB schema name in the table
1115 declaration, like so...
1117 package MyDatabase::Main::Artist;
1118 use base qw/DBIx::Class/;
1119 __PACKAGE__->load_components(qw/PK::Auto Core/);
1121 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1123 __PACKAGE__->add_columns(qw/ artist_id name /);
1124 __PACKAGE__->set_primary_key('artist_id');
1125 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1129 Whatever string you specify there will be used to build the "FROM" clause in SQL
1132 The big drawback to this is you now have DB schema names hardcoded in your
1133 class files. This becomes especially troublesome if you have multiple instances
1134 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1135 the DB schemas are named based on the environment (e.g. database1_dev).
1137 However, one can dynamically "map" to the proper DB schema by overriding the
1138 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1139 building a renaming facility, like so:
1141 package MyDatabase::Schema;
1144 extends 'DBIx::Class::Schema';
1146 around connection => sub {
1147 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1149 my $postfix = delete $attr->{schema_name_postfix};
1154 $self->append_db_name($postfix);
1158 sub append_db_name {
1159 my ( $self, $postfix ) = @_;
1163 { $_->name =~ /^\w+\./mx }
1165 { $self->source($_) }
1168 foreach my $source (@sources_with_db) {
1169 my $name = $source->name;
1170 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1172 $source->name($name);
1178 By overridding the L<connection|DBIx::Class::Schama/connection>
1179 method and extracting a custom option from the provided \%attr hashref one can
1180 then simply iterate over all the Schema's ResultSources, renaming them as
1183 To use this facility, simply add or modify the \%attr hashref that is passed to
1184 L<connection|DBIx::Class::Schama/connect>, as follows:
1187 = MyDatabase::Schema->connect(
1192 schema_name_postfix => '_dev'
1193 # ... Other options as desired ...
1196 Obviously, one could accomplish even more advanced mapping via a hash map or a
1201 As of version 0.04001, there is improved transaction support in
1202 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1203 example of the recommended way to use it:
1205 my $genus = $schema->resultset('Genus')->find(12);
1207 my $coderef2 = sub {
1212 my $coderef1 = sub {
1213 $genus->add_to_species({ name => 'troglodyte' });
1216 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1217 return $genus->species;
1222 $rs = $schema->txn_do($coderef1);
1225 if ($@) { # Transaction failed
1226 die "the sky is falling!" #
1227 if ($@ =~ /Rollback failed/); # Rollback failed
1229 deal_with_failed_transaction();
1232 Nested transactions will work as expected. That is, only the outermost
1233 transaction will actually issue a commit to the $dbh, and a rollback
1234 at any level of any transaction will cause the entire nested
1235 transaction to fail. Support for savepoints and for true nested
1236 transactions (for databases that support them) will hopefully be added
1241 =head2 Creating Schemas From An Existing Database
1243 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1244 L<DBIx::Class::Schema> and associated sources by examining the database.
1246 The recommend way of achieving this is to use the
1247 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1249 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1250 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1252 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1253 source definitions for all the tables found in the C<foo> database.
1255 =head2 Creating DDL SQL
1257 The following functionality requires you to have L<SQL::Translator>
1258 (also known as "SQL Fairy") installed.
1260 To create a set of database-specific .sql files for the above schema:
1262 my $schema = My::Schema->connect($dsn);
1263 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1268 By default this will create schema files in the current directory, for
1269 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1271 To create a new database using the schema:
1273 my $schema = My::Schema->connect($dsn);
1274 $schema->deploy({ add_drop_tables => 1});
1276 To import created .sql files using the mysql client:
1278 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1280 To create C<ALTER TABLE> conversion scripts to update a database to a
1281 newer version of your schema at a later point, first set a new
1282 C<$VERSION> in your Schema file, then:
1284 my $schema = My::Schema->connect($dsn);
1285 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1291 This will produce new database-specific .sql files for the new version
1292 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1293 requires that the files for 0.1 as created above are available in the
1294 given directory to diff against.
1296 =head2 Select from dual
1298 Dummy tables are needed by some databases to allow calling functions
1299 or expressions that aren't based on table content, for examples of how
1300 this applies to various database types, see:
1301 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1303 Note: If you're using Oracles dual table don't B<ever> do anything
1304 other than a select, if you CRUD on your dual table you *will* break
1307 Make a table class as you would for any other table
1309 package MyAppDB::Dual;
1312 use base 'DBIx::Class';
1313 __PACKAGE__->load_components("Core");
1314 __PACKAGE__->table("Dual");
1315 __PACKAGE__->add_columns(
1317 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1320 Once you've loaded your table class select from it using C<select>
1321 and C<as> instead of C<columns>
1323 my $rs = $schema->resultset('Dual')->search(undef,
1324 { select => [ 'sydate' ],
1329 All you have to do now is be careful how you access your resultset, the below
1330 will not work because there is no column called 'now' in the Dual table class
1332 while (my $dual = $rs->next) {
1333 print $dual->now."\n";
1335 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1337 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1338 your Dual class for whatever you wanted to select from dual, but that's just
1339 silly, instead use C<get_column>
1341 while (my $dual = $rs->next) {
1342 print $dual->get_column('now')."\n";
1347 my $cursor = $rs->cursor;
1348 while (my @vals = $cursor->next) {
1349 print $vals[0]."\n";
1352 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1353 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1354 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1355 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1356 L<SQL::Translator> to not create table dual:
1359 add_drop_table => 1,
1360 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1362 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1364 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1366 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1367 while ( my $dual = $rs->next ) {
1368 print $dual->{now}."\n";
1371 Here are some example C<select> conditions to illustrate the different syntax
1372 you could use for doing stuff like
1373 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1375 # get a sequence value
1376 select => [ 'A_SEQ.nextval' ],
1378 # get create table sql
1379 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1381 # get a random num between 0 and 100
1382 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1385 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1388 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1390 # which day of the week were you born on?
1391 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1393 # select 16 rows from dual
1394 select => [ "'hello'" ],
1396 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1400 =head2 Adding Indexes And Functions To Your SQL
1402 Often you will want indexes on columns on your table to speed up searching. To
1403 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1404 class (refer to the advanced
1405 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1406 to share a hook between multiple sources):
1408 package My::Schema::Result::Artist;
1410 __PACKAGE__->table('artist');
1411 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1413 sub sqlt_deploy_hook {
1414 my ($self, $sqlt_table) = @_;
1416 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1421 Sometimes you might want to change the index depending on the type of the
1422 database for which SQL is being generated:
1424 my ($db_type = $sqlt_table->schema->translator->producer_type)
1425 =~ s/^SQL::Translator::Producer:://;
1427 You can also add hooks to the schema level to stop certain tables being
1434 sub sqlt_deploy_hook {
1435 my ($self, $sqlt_schema) = @_;
1437 $sqlt_schema->drop_table('table_name');
1440 You could also add views, procedures or triggers to the output using
1441 L<SQL::Translator::Schema/add_view>,
1442 L<SQL::Translator::Schema/add_procedure> or
1443 L<SQL::Translator::Schema/add_trigger>.
1446 =head2 Schema versioning
1448 The following example shows simplistically how you might use DBIx::Class to
1449 deploy versioned schemas to your customers. The basic process is as follows:
1455 Create a DBIx::Class schema
1467 Modify schema to change functionality
1471 Deploy update to customers
1475 B<Create a DBIx::Class schema>
1477 This can either be done manually, or generated from an existing database as
1478 described under L</Creating Schemas From An Existing Database>
1482 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1484 B<Deploy to customers>
1486 There are several ways you could deploy your schema. These are probably
1487 beyond the scope of this recipe, but might include:
1493 Require customer to apply manually using their RDBMS.
1497 Package along with your app, making database dump/schema update/tests
1498 all part of your install.
1502 B<Modify the schema to change functionality>
1504 As your application evolves, it may be necessary to modify your schema
1505 to change functionality. Once the changes are made to your schema in
1506 DBIx::Class, export the modified schema and the conversion scripts as
1507 in L</Creating DDL SQL>.
1509 B<Deploy update to customers>
1511 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1512 Schema class. This will add a new table to your database called
1513 C<dbix_class_schema_vesion> which will keep track of which version is installed
1514 and warn if the user trys to run a newer schema version than the
1515 database thinks it has.
1517 Alternatively, you can send the conversion sql scripts to your
1520 =head2 Setting quoting for the generated SQL
1522 If the database contains column names with spaces and/or reserved words, they
1523 need to be quoted in the SQL queries. This is done using:
1525 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1526 $schema->storage->sql_maker->name_sep('.');
1528 The first sets the quote characters. Either a pair of matching
1529 brackets, or a C<"> or C<'>:
1531 $schema->storage->sql_maker->quote_char('"');
1533 Check the documentation of your database for the correct quote
1534 characters to use. C<name_sep> needs to be set to allow the SQL
1535 generator to put the quotes the correct place.
1537 In most cases you should set these as part of the arguments passed to
1538 L<DBIx::Class::Schema/connect>:
1540 my $schema = My::Schema->connect(
1550 In some cases, quoting will be required for all users of a schema. To enforce
1551 this, you can also overload the C<connection> method for your schema class:
1555 my $rv = $self->next::method( @_ );
1556 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1557 $rv->storage->sql_maker->name_sep('.');
1561 =head2 Setting limit dialect for SQL::Abstract::Limit
1563 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1564 the remote SQL server by looking at the database handle. This is a
1565 common problem when using the DBD::JDBC, since the DBD-driver only
1566 know that in has a Java-driver available, not which JDBC driver the
1567 Java component has loaded. This specifically sets the limit_dialect
1568 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1571 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1573 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1574 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1576 The limit dialect can also be set at connect time by specifying a
1577 C<limit_dialect> key in the final hash as shown above.
1579 =head2 Working with PostgreSQL array types
1581 You can also assign values to PostgreSQL array columns by passing array
1582 references in the C<\%columns> (C<\%vals>) hashref of the
1583 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1586 $resultset->create({
1587 numbers => [1, 2, 3]
1592 numbers => [1, 2, 3]
1599 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1600 methods) you cannot directly use array references (since this is interpreted as
1601 a list of values to be C<OR>ed), but you can use the following syntax to force
1602 passing them as bind values:
1606 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1610 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1611 placeholders and bind values (subqueries)> for more explanation. Note that
1612 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1613 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1614 arrayrefs together with the column name, like this: C<< [column_name => value]
1617 =head1 BOOTSTRAPPING/MIGRATING
1619 =head2 Easy migration from class-based to schema-based setup
1621 You want to start using the schema-based approach to L<DBIx::Class>
1622 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1623 of existing classes that you don't want to move by hand. Try this nifty script
1627 use SQL::Translator;
1629 my $schema = MyDB->schema_instance;
1631 my $translator = SQL::Translator->new(
1632 debug => $debug || 0,
1633 trace => $trace || 0,
1634 no_comments => $no_comments || 0,
1635 show_warnings => $show_warnings || 0,
1636 add_drop_table => $add_drop_table || 0,
1637 validate => $validate || 0,
1639 'DBIx::Schema' => $schema,
1642 'prefix' => 'My::Schema',
1646 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1647 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1649 my $output = $translator->translate(@args) or die
1650 "Error: " . $translator->error;
1654 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1655 namespace, which is currently left as an exercise for the reader.
1657 =head1 OVERLOADING METHODS
1659 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1660 method calls, useful for things like default values and triggers. You have to
1661 use calls to C<next::method> to overload methods. More information on using
1662 L<Class::C3> with L<DBIx::Class> can be found in
1663 L<DBIx::Class::Manual::Component>.
1665 =head2 Setting default values for a row
1667 It's as simple as overriding the C<new> method. Note the use of
1671 my ( $class, $attrs ) = @_;
1673 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1675 my $new = $class->next::method($attrs);
1680 For more information about C<next::method>, look in the L<Class::C3>
1681 documentation. See also L<DBIx::Class::Manual::Component> for more
1682 ways to write your own base classes to do this.
1684 People looking for ways to do "triggers" with DBIx::Class are probably
1685 just looking for this.
1687 =head2 Changing one field whenever another changes
1689 For example, say that you have three columns, C<id>, C<number>, and
1690 C<squared>. You would like to make changes to C<number> and have
1691 C<squared> be automagically set to the value of C<number> squared.
1692 You can accomplish this by overriding C<store_column>:
1695 my ( $self, $name, $value ) = @_;
1696 if ($name eq 'number') {
1697 $self->squared($value * $value);
1699 $self->next::method($name, $value);
1702 Note that the hard work is done by the call to C<next::method>, which
1703 redispatches your call to store_column in the superclass(es).
1705 =head2 Automatically creating related objects
1707 You might have a class C<Artist> which has many C<CD>s. Further, you
1708 want to create a C<CD> object every time you insert an C<Artist> object.
1709 You can accomplish this by overriding C<insert> on your objects:
1712 my ( $self, @args ) = @_;
1713 $self->next::method(@args);
1714 $self->cds->new({})->fill_from_artist($self)->insert;
1718 where C<fill_from_artist> is a method you specify in C<CD> which sets
1719 values in C<CD> based on the data in the C<Artist> object you pass in.
1721 =head2 Wrapping/overloading a column accessor
1725 Say you have a table "Camera" and want to associate a description
1726 with each camera. For most cameras, you'll be able to generate the description from
1727 the other columns. However, in a few special cases you may want to associate a
1728 custom description with a camera.
1732 In your database schema, define a description field in the "Camera" table that
1733 can contain text and null values.
1735 In DBIC, we'll overload the column accessor to provide a sane default if no
1736 custom description is defined. The accessor will either return or generate the
1737 description, depending on whether the field is null or not.
1739 First, in your "Camera" schema class, define the description field as follows:
1741 __PACKAGE__->add_columns(description => { accessor => '_description' });
1743 Next, we'll define the accessor-wrapper subroutine:
1748 # If there is an update to the column, we'll let the original accessor
1750 return $self->_description(@_) if @_;
1752 # Fetch the column value.
1753 my $description = $self->_description;
1755 # If there's something in the description field, then just return that.
1756 return $description if defined $description && length $descripton;
1758 # Otherwise, generate a description.
1759 return $self->generate_description;
1762 =head1 DEBUGGING AND PROFILING
1764 =head2 DBIx::Class objects with Data::Dumper
1766 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1767 be hard to find the pertinent data in all the data it can generate.
1768 Specifically, if one naively tries to use it like so,
1772 my $cd = $schema->resultset('CD')->find(1);
1775 several pages worth of data from the CD object's schema and result source will
1776 be dumped to the screen. Since usually one is only interested in a few column
1777 values of the object, this is not very helpful.
1779 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1780 it. Simply define a hook that L<Data::Dumper> will call on the object before
1781 dumping it. For example,
1788 result_source => undef,
1796 local $Data::Dumper::Freezer = '_dumper_hook';
1798 my $cd = $schema->resultset('CD')->find(1);
1800 # dumps $cd without its ResultSource
1802 If the structure of your schema is such that there is a common base class for
1803 all your table classes, simply put a method similar to C<_dumper_hook> in the
1804 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1805 will automagically clean up your data before printing it. See
1806 L<Data::Dumper/EXAMPLES> for more information.
1810 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1811 executed as well as notifications of query completion and transaction
1812 begin/commit. If you'd like to profile the SQL you can subclass the
1813 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1816 package My::Profiler;
1819 use base 'DBIx::Class::Storage::Statistics';
1821 use Time::HiRes qw(time);
1830 $self->print("Executing $sql: ".join(', ', @params)."\n");
1839 my $elapsed = sprintf("%0.4f", time() - $start);
1840 $self->print("Execution took $elapsed seconds.\n");
1846 You can then install that class as the debugging object:
1848 __PACKAGE__->storage->debugobj(new My::Profiler());
1849 __PACKAGE__->storage->debug(1);
1851 A more complicated example might involve storing each execution of SQL in an
1859 my $elapsed = time() - $start;
1860 push(@{ $calls{$sql} }, {
1866 You could then create average, high and low execution times for an SQL
1867 statement and dig down to see if certain parameters cause aberrant behavior.
1868 You might want to check out L<DBIx::Class::QueryLog> as well.
1870 =head1 STARTUP SPEED
1872 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1873 as the ORM loads all the relevant classes. This section examines
1874 techniques for reducing the startup delay.
1876 These tips are are listed in order of decreasing effectiveness - so the
1877 first tip, if applicable, should have the greatest effect on your
1880 =head2 Statically Define Your Schema
1883 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1884 classes dynamically based on the database schema then there will be a
1885 significant startup delay.
1887 For production use a statically defined schema (which can be generated
1888 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1889 the database schema once - see
1890 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1891 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1892 details on creating static schemas from a database).
1894 =head2 Move Common Startup into a Base Class
1896 Typically L<DBIx::Class> result classes start off with
1898 use base qw/DBIx::Class/;
1899 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1901 If this preamble is moved into a common base class:-
1905 use base qw/DBIx::Class/;
1906 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1909 and each result class then uses this as a base:-
1911 use base qw/MyDBICbase/;
1913 then the load_components is only performed once, which can result in a
1914 considerable startup speedup for schemas with many classes.
1916 =head2 Explicitly List Schema Result Classes
1918 The schema class will normally contain
1920 __PACKAGE__->load_classes();
1922 to load the result classes. This will use L<Module::Find|Module::Find>
1923 to find and load the appropriate modules. Explicitly defining the
1924 classes you wish to load will remove the overhead of
1925 L<Module::Find|Module::Find> and the related directory operations:
1927 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1929 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1930 syntax to load the appropriate classes there is not a direct alternative
1931 avoiding L<Module::Find|Module::Find>.
1935 =head2 Cached statements
1937 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
1938 This is normally a good idea, but if too many statements are cached, the database may use too much
1939 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
1940 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
1942 # print all currently cached prepared statements
1943 print for keys %{$schema->storage->dbh->{CachedKids}};
1944 # get a count of currently cached prepared statements
1945 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
1947 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
1950 my $kids = $schema->storage->dbh->{CachedKids};
1951 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
1953 But what you probably want is to expire unused statements and not those that are used frequently.
1954 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
1958 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
1959 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },