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 See also L</Using SQL functions on the left hand side of a comparison>.
252 =head2 SELECT DISTINCT with multiple columns
254 my $rs = $schema->resultset('Artist')->search(
257 columns => [ qw/artist_id name rank/ ],
262 my $rs = $schema->resultset('Artist')->search(
265 columns => [ qw/artist_id name rank/ ],
266 group_by => [ qw/artist_id name rank/ ],
271 # SELECT me.artist_id, me.name, me.rank
273 # GROUP BY artist_id, name, rank
275 =head2 SELECT COUNT(DISTINCT colname)
277 my $rs = $schema->resultset('Artist')->search(
280 columns => [ qw/name/ ],
285 my $rs = $schema->resultset('Artist')->search(
288 columns => [ qw/name/ ],
289 group_by => [ qw/name/ ],
293 my $count = $rs->count;
296 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
298 =head2 Grouping results
300 L<DBIx::Class> supports C<GROUP BY> as follows:
302 my $rs = $schema->resultset('Artist')->search(
306 select => [ 'name', { count => 'cds.id' } ],
307 as => [qw/ name cd_count /],
308 group_by => [qw/ name /]
313 # SELECT name, COUNT( cd.id ) FROM artist
314 # LEFT JOIN cd ON artist.id = cd.artist
317 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
318 are in any way unsure about the use of the attributes above (C< join
319 >, C< select >, C< as > and C< group_by >).
321 =head2 Subqueries (EXPERIMENTAL)
323 You can write subqueries relatively easily in DBIC.
325 my $inside_rs = $schema->resultset('Artist')->search({
326 name => [ 'Billy Joel', 'Brittany Spears' ],
329 my $rs = $schema->resultset('CD')->search({
330 artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
333 The usual operators ( =, !=, IN, NOT IN, etc) are supported.
335 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
336 The following will B<not> work:
338 my $rs = $schema->resultset('CD')->search({
339 artist_id => $inside_rs->get_column('id')->as_query,
344 Subqueries are supported in the where clause (first hashref), and in the
345 from, select, and +select attributes.
347 =head3 Correlated subqueries
349 my $cdrs = $schema->resultset('CD');
350 my $rs = $cdrs->search({
352 '=' => $cdrs->search(
353 { artist_id => { '=' => \'me.artist_id' } },
355 )->get_column('year')->max_rs->as_query,
359 That creates the following SQL:
361 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
364 SELECT MAX(inner.year)
366 WHERE artist_id = me.artist_id
371 Please note that subqueries are considered an experimental feature.
373 =head2 Predefined searches
375 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
376 and defining often used searches as methods:
378 package My::DBIC::ResultSet::CD;
381 use base 'DBIx::Class::ResultSet';
383 sub search_cds_ordered {
386 return $self->search(
388 { order_by => 'name DESC' },
394 To use your resultset, first tell DBIx::Class to create an instance of it
395 for you, in your My::DBIC::Schema::CD class:
397 # class definition as normal
398 __PACKAGE__->load_components(qw/ Core /);
399 __PACKAGE__->table('cd');
401 # tell DBIC to use the custom ResultSet class
402 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
404 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
406 Then call your new method in your code:
408 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
410 =head2 Using SQL functions on the left hand side of a comparison
412 Using SQL functions on the left hand side of a comparison is generally
413 not a good idea since it requires a scan of the entire table. However,
414 it can be accomplished with C<DBIx::Class> when necessary.
416 If you do not have quoting on, simply include the function in your search
417 specification as you would any column:
419 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
421 With quoting on, or for a more portable solution, use the C<where>
424 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
428 (When the bind args ordering bug is fixed, this technique will be better
429 and can replace the one above.)
431 With quoting on, or for a more portable solution, use the C<where> and
435 where => \'YEAR(date_of_birth) = ?',
441 =head1 JOINS AND PREFETCHING
443 =head2 Using joins and prefetch
445 You can use the C<join> attribute to allow searching on, or sorting your
446 results by, one or more columns in a related table.
448 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
450 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
452 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
454 my $rs = $schema->resultset('CD')->search(
456 'artists.name' => 'Bob Marley'
459 join => 'artists', # join the artist table
464 # SELECT cd.* FROM cd
465 # JOIN artist ON cd.artist = artist.id
466 # WHERE artist.name = 'Bob Marley'
468 In that example both the join, and the condition use the relationship name rather than the table name
469 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
471 If required, you can now sort on any column in the related tables by including
472 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
474 my $rs = $schema->resultset('CD')->search(
476 'artists.name' => 'Bob Marley'
480 order_by => [qw/ artists.name /]
485 # SELECT cd.* FROM cd
486 # JOIN artist ON cd.artist = artist.id
487 # WHERE artist.name = 'Bob Marley'
488 # ORDER BY artist.name
490 Note that the C<join> attribute should only be used when you need to search or
491 sort using columns in a related table. Joining related tables when you only
492 need columns from the main table will make performance worse!
494 Now let's say you want to display a list of CDs, each with the name of the
495 artist. The following will work fine:
497 while (my $cd = $rs->next) {
498 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
501 There is a problem however. We have searched both the C<cd> and C<artist> tables
502 in our main query, but we have only returned data from the C<cd> table. To get
503 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
506 SELECT artist.* FROM artist WHERE artist.id = ?
508 A statement like the one above will run for each and every CD returned by our
509 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
512 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
513 This allows you to fetch results from related tables in advance:
515 my $rs = $schema->resultset('CD')->search(
517 'artists.name' => 'Bob Marley'
521 order_by => [qw/ artists.name /],
522 prefetch => 'artists' # return artist data too!
526 # Equivalent SQL (note SELECT from both "cd" and "artist"):
527 # SELECT cd.*, artist.* FROM cd
528 # JOIN artist ON cd.artist = artist.id
529 # WHERE artist.name = 'Bob Marley'
530 # ORDER BY artist.name
532 The code to print the CD list remains the same:
534 while (my $cd = $rs->next) {
535 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
538 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
539 so no additional SQL statements are executed. You now have a much more
542 Also note that C<prefetch> should only be used when you know you will
543 definitely use data from a related table. Pre-fetching related tables when you
544 only need columns from the main table will make performance worse!
546 =head2 Multiple joins
548 In the examples above, the C<join> attribute was a scalar. If you
549 pass an array reference instead, you can join to multiple tables. In
550 this example, we want to limit the search further, using
553 # Relationships defined elsewhere:
554 # CD->belongs_to('artist' => 'Artist');
555 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
556 my $rs = $schema->resultset('CD')->search(
558 'artist.name' => 'Bob Marley'
559 'liner_notes.notes' => { 'like', '%some text%' },
562 join => [qw/ artist liner_notes /],
563 order_by => [qw/ artist.name /],
568 # SELECT cd.*, artist.*, liner_notes.* FROM cd
569 # JOIN artist ON cd.artist = artist.id
570 # JOIN liner_notes ON cd.id = liner_notes.cd
571 # WHERE artist.name = 'Bob Marley'
572 # ORDER BY artist.name
574 =head2 Multi-step joins
576 Sometimes you want to join more than one relationship deep. In this example,
577 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
578 contain a specific string:
580 # Relationships defined elsewhere:
581 # Artist->has_many('cds' => 'CD', 'artist');
582 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
584 my $rs = $schema->resultset('Artist')->search(
586 'liner_notes.notes' => { 'like', '%some text%' },
590 'cds' => 'liner_notes'
596 # SELECT artist.* FROM artist
597 # LEFT JOIN cd ON artist.id = cd.artist
598 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
599 # WHERE liner_notes.notes LIKE '%some text%'
601 Joins can be nested to an arbitrary level. So if we decide later that we
602 want to reduce the number of Artists returned based on who wrote the liner
605 # Relationship defined elsewhere:
606 # LinerNotes->belongs_to('author' => 'Person');
608 my $rs = $schema->resultset('Artist')->search(
610 'liner_notes.notes' => { 'like', '%some text%' },
611 'author.name' => 'A. Writer'
616 'liner_notes' => 'author'
623 # SELECT artist.* FROM artist
624 # LEFT JOIN cd ON artist.id = cd.artist
625 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
626 # LEFT JOIN author ON author.id = liner_notes.author
627 # WHERE liner_notes.notes LIKE '%some text%'
628 # AND author.name = 'A. Writer'
630 =head2 Multi-step and multiple joins
632 With various combinations of array and hash references, you can join
633 tables in any combination you desire. For example, to join Artist to
634 CD and Concert, and join CD to LinerNotes:
636 # Relationships defined elsewhere:
637 # Artist->has_many('concerts' => 'Concert', 'artist');
639 my $rs = $schema->resultset('Artist')->search(
652 # SELECT artist.* FROM artist
653 # LEFT JOIN cd ON artist.id = cd.artist
654 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
655 # LEFT JOIN concert ON artist.id = concert.artist
657 =head2 Multi-step prefetch
659 C<prefetch> can be nested more than one relationship
660 deep using the same syntax as a multi-step join:
662 my $rs = $schema->resultset('Tag')->search(
672 # SELECT tag.*, cd.*, artist.* FROM tag
673 # JOIN cd ON tag.cd = cd.id
674 # JOIN artist ON cd.artist = artist.id
676 Now accessing our C<cd> and C<artist> relationships does not need additional
679 my $tag = $rs->first;
680 print $tag->cd->artist->name;
682 =head1 ROW-LEVEL OPERATIONS
684 =head2 Retrieving a row object's Schema
686 It is possible to get a Schema object from a row object like so:
688 my $schema = $cd->result_source->schema;
689 # use the schema as normal:
690 my $artist_rs = $schema->resultset('Artist');
692 This can be useful when you don't want to pass around a Schema object to every
695 =head2 Getting the value of the primary key for the last database insert
697 AKA getting last_insert_id
699 Thanks to the core component PK::Auto, this is straightforward:
701 my $foo = $rs->create(\%blah);
703 my $id = $foo->id; # foo->my_primary_key_field will also work.
705 If you are not using autoincrementing primary keys, this will probably
706 not work, but then you already know the value of the last primary key anyway.
708 =head2 Stringification
710 Employ the standard stringification technique by using the L<overload>
713 To make an object stringify itself as a single column, use something
714 like this (replace C<name> with the column/method of your choice):
716 use overload '""' => sub { shift->name}, fallback => 1;
718 For more complex stringification, you can use an anonymous subroutine:
720 use overload '""' => sub { $_[0]->name . ", " .
721 $_[0]->address }, fallback => 1;
723 =head3 Stringification Example
725 Suppose we have two tables: C<Product> and C<Category>. The table
728 Product(id, Description, category)
729 Category(id, Description)
731 C<category> is a foreign key into the Category table.
733 If you have a Product object C<$obj> and write something like
737 things will not work as expected.
739 To obtain, for example, the category description, you should add this
740 method to the class defining the Category table:
742 use overload "" => sub {
745 return $self->Description;
748 =head2 Want to know if find_or_create found or created a row?
750 Just use C<find_or_new> instead, then check C<in_storage>:
752 my $obj = $rs->find_or_new({ blah => 'blarg' });
753 unless ($obj->in_storage) {
755 # do whatever else you wanted if it was a new row
758 =head2 Static sub-classing DBIx::Class result classes
760 AKA adding additional relationships/methods/etc. to a model for a
761 specific usage of the (shared) model.
765 package My::App::Schema;
767 use base DBIx::Class::Schema;
769 # load subclassed classes from My::App::Schema::Result/ResultSet
770 __PACKAGE__->load_namespaces;
772 # load classes from shared model
774 'My::Shared::Model::Result' => [qw/
781 B<Result-Subclass definition>
783 package My::App::Schema::Result::Baz;
787 use base My::Shared::Model::Result::Baz;
789 # WARNING: Make sure you call table() again in your subclass,
790 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
791 # and the class name is not correctly registered as a source
792 __PACKAGE__->table('baz');
794 sub additional_method {
795 return "I'm an additional method only needed by this app";
800 =head2 Dynamic Sub-classing DBIx::Class proxy classes
802 AKA multi-class object inflation from one table
804 L<DBIx::Class> classes are proxy classes, therefore some different
805 techniques need to be employed for more than basic subclassing. In
806 this example we have a single user table that carries a boolean bit
807 for admin. We would like like to give the admin users
808 objects (L<DBIx::Class::Row>) the same methods as a regular user but
809 also special admin only methods. It doesn't make sense to create two
810 seperate proxy-class files for this. We would be copying all the user
811 methods into the Admin class. There is a cleaner way to accomplish
814 Overriding the C<inflate_result> method within the User proxy-class
815 gives us the effect we want. This method is called by
816 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
817 grab the object being returned, inspect the values we are looking for,
818 bless it if it's an admin object, and then return it. See the example
825 use base qw/DBIx::Class::Schema/;
827 __PACKAGE__->load_namespaces;
832 B<Proxy-Class definitions>
834 package My::Schema::Result::User;
838 use base qw/DBIx::Class/;
840 ### Define what our admin class is, for ensure_class_loaded()
841 my $admin_class = __PACKAGE__ . '::Admin';
843 __PACKAGE__->load_components(qw/Core/);
845 __PACKAGE__->table('users');
847 __PACKAGE__->add_columns(qw/user_id email password
848 firstname lastname active
851 __PACKAGE__->set_primary_key('user_id');
855 my $ret = $self->next::method(@_);
856 if( $ret->admin ) {### If this is an admin, rebless for extra functions
857 $self->ensure_class_loaded( $admin_class );
858 bless $ret, $admin_class;
864 print "I am a regular user.\n";
871 package My::Schema::Result::User::Admin;
875 use base qw/My::Schema::Result::User/;
877 # This line is important
878 __PACKAGE__->table('users');
882 print "I am an admin.\n";
888 print "I am doing admin stuff\n";
900 my $user_data = { email => 'someguy@place.com',
904 my $admin_data = { email => 'someadmin@adminplace.com',
908 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
910 $schema->resultset('User')->create( $user_data );
911 $schema->resultset('User')->create( $admin_data );
913 ### Now we search for them
914 my $user = $schema->resultset('User')->single( $user_data );
915 my $admin = $schema->resultset('User')->single( $admin_data );
917 print ref $user, "\n";
918 print ref $admin, "\n";
920 print $user->password , "\n"; # pass1
921 print $admin->password , "\n";# pass2; inherited from User
922 print $user->hello , "\n";# I am a regular user.
923 print $admin->hello, "\n";# I am an admin.
925 ### The statement below will NOT print
926 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
927 ### The statement below will print
928 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
930 =head2 Skip row object creation for faster results
932 DBIx::Class is not built for speed, it's built for convenience and
933 ease of use, but sometimes you just need to get the data, and skip the
936 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
938 my $rs = $schema->resultset('CD');
940 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
942 my $hash_ref = $rs->find(1);
946 Beware, changing the Result class using
947 L<DBIx::Class::ResultSet/result_class> will replace any existing class
948 completely including any special components loaded using
949 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
951 =head2 Get raw data for blindingly fast results
953 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
954 above is not fast enough for you, you can use a DBIx::Class to return values
955 exactly as they come out of the database with none of the convenience methods
958 This is used like so:
960 my $cursor = $rs->cursor
961 while (my @vals = $cursor->next) {
962 # use $val[0..n] here
965 You will need to map the array offsets to particular columns (you can
966 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
968 =head1 RESULTSET OPERATIONS
970 =head2 Getting Schema from a ResultSet
972 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
974 $rs->result_source->schema
976 =head2 Getting Columns Of Data
980 If you want to find the sum of a particular column there are several
981 ways, the obvious one is to use search:
983 my $rs = $schema->resultset('Items')->search(
986 select => [ { sum => 'Cost' } ],
987 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
990 my $tc = $rs->first->get_column('total_cost');
992 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
993 returned when you ask the C<ResultSet> for a column using
996 my $cost = $schema->resultset('Items')->get_column('Cost');
999 With this you can also do:
1001 my $minvalue = $cost->min;
1002 my $maxvalue = $cost->max;
1004 Or just iterate through the values of this column only:
1006 while ( my $c = $cost->next ) {
1010 foreach my $c ($cost->all) {
1014 C<ResultSetColumn> only has a limited number of built-in functions. If
1015 you need one that it doesn't have, then you can use the C<func> method
1018 my $avg = $cost->func('AVERAGE');
1020 This will cause the following SQL statement to be run:
1022 SELECT AVERAGE(Cost) FROM Items me
1024 Which will of course only work if your database supports this function.
1025 See L<DBIx::Class::ResultSetColumn> for more documentation.
1027 =head2 Creating a result set from a set of rows
1029 Sometimes you have a (set of) row objects that you want to put into a
1030 resultset without the need to hit the DB again. You can do that by using the
1031 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1033 my @uploadable_groups;
1034 while (my $group = $groups->next) {
1035 if ($group->can_upload($self)) {
1036 push @uploadable_groups, $group;
1039 my $new_rs = $self->result_source->resultset;
1040 $new_rs->set_cache(\@uploadable_groups);
1044 =head1 USING RELATIONSHIPS
1046 =head2 Create a new row in a related table
1048 my $author = $book->create_related('author', { name => 'Fred'});
1050 =head2 Search in a related table
1052 Only searches for books named 'Titanic' by the author in $author.
1054 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1056 =head2 Delete data in a related table
1058 Deletes only the book named Titanic by the author in $author.
1060 $author->delete_related('books', { name => 'Titanic' });
1062 =head2 Ordering a relationship result set
1064 If you always want a relation to be ordered, you can specify this when you
1065 create the relationship.
1067 To order C<< $book->pages >> by descending page_number, create the relation
1070 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
1072 =head2 Filtering a relationship result set
1074 If you want to get a filtered result set, you can just add add to $attr as follows:
1076 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1078 =head2 Many-to-many relationships
1080 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1083 use base 'DBIx::Class';
1084 __PACKAGE__->load_components('Core');
1085 __PACKAGE__->table('user');
1086 __PACKAGE__->add_columns(qw/id name/);
1087 __PACKAGE__->set_primary_key('id');
1088 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1089 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1091 package My::UserAddress;
1092 use base 'DBIx::Class';
1093 __PACKAGE__->load_components('Core');
1094 __PACKAGE__->table('user_address');
1095 __PACKAGE__->add_columns(qw/user address/);
1096 __PACKAGE__->set_primary_key(qw/user address/);
1097 __PACKAGE__->belongs_to('user' => 'My::User');
1098 __PACKAGE__->belongs_to('address' => 'My::Address');
1100 package My::Address;
1101 use base 'DBIx::Class';
1102 __PACKAGE__->load_components('Core');
1103 __PACKAGE__->table('address');
1104 __PACKAGE__->add_columns(qw/id street town area_code country/);
1105 __PACKAGE__->set_primary_key('id');
1106 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1107 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1109 $rs = $user->addresses(); # get all addresses for a user
1110 $rs = $address->users(); # get all users for an address
1112 =head2 Relationships across DB schemas
1114 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1115 is easy as long as the schemas themselves are all accessible via the same DBI
1116 connection. In most cases, this means that they are on the same database host
1117 as each other and your connecting database user has the proper permissions to them.
1119 To accomplish this one only needs to specify the DB schema name in the table
1120 declaration, like so...
1122 package MyDatabase::Main::Artist;
1123 use base qw/DBIx::Class/;
1124 __PACKAGE__->load_components(qw/PK::Auto Core/);
1126 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1128 __PACKAGE__->add_columns(qw/ artist_id name /);
1129 __PACKAGE__->set_primary_key('artist_id');
1130 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1134 Whatever string you specify there will be used to build the "FROM" clause in SQL
1137 The big drawback to this is you now have DB schema names hardcoded in your
1138 class files. This becomes especially troublesome if you have multiple instances
1139 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1140 the DB schemas are named based on the environment (e.g. database1_dev).
1142 However, one can dynamically "map" to the proper DB schema by overriding the
1143 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1144 building a renaming facility, like so:
1146 package MyDatabase::Schema;
1149 extends 'DBIx::Class::Schema';
1151 around connection => sub {
1152 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1154 my $postfix = delete $attr->{schema_name_postfix};
1159 $self->append_db_name($postfix);
1163 sub append_db_name {
1164 my ( $self, $postfix ) = @_;
1168 { $_->name =~ /^\w+\./mx }
1170 { $self->source($_) }
1173 foreach my $source (@sources_with_db) {
1174 my $name = $source->name;
1175 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1177 $source->name($name);
1183 By overridding the L<connection|DBIx::Class::Schama/connection>
1184 method and extracting a custom option from the provided \%attr hashref one can
1185 then simply iterate over all the Schema's ResultSources, renaming them as
1188 To use this facility, simply add or modify the \%attr hashref that is passed to
1189 L<connection|DBIx::Class::Schama/connect>, as follows:
1192 = MyDatabase::Schema->connect(
1197 schema_name_postfix => '_dev'
1198 # ... Other options as desired ...
1201 Obviously, one could accomplish even more advanced mapping via a hash map or a
1206 As of version 0.04001, there is improved transaction support in
1207 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1208 example of the recommended way to use it:
1210 my $genus = $schema->resultset('Genus')->find(12);
1212 my $coderef2 = sub {
1217 my $coderef1 = sub {
1218 $genus->add_to_species({ name => 'troglodyte' });
1221 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1222 return $genus->species;
1227 $rs = $schema->txn_do($coderef1);
1230 if ($@) { # Transaction failed
1231 die "the sky is falling!" #
1232 if ($@ =~ /Rollback failed/); # Rollback failed
1234 deal_with_failed_transaction();
1237 Nested transactions will work as expected. That is, only the outermost
1238 transaction will actually issue a commit to the $dbh, and a rollback
1239 at any level of any transaction will cause the entire nested
1240 transaction to fail. Support for savepoints and for true nested
1241 transactions (for databases that support them) will hopefully be added
1246 =head2 Creating Schemas From An Existing Database
1248 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1249 L<DBIx::Class::Schema> and associated sources by examining the database.
1251 The recommend way of achieving this is to use the
1252 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1254 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1255 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1257 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1258 source definitions for all the tables found in the C<foo> database.
1260 =head2 Creating DDL SQL
1262 The following functionality requires you to have L<SQL::Translator>
1263 (also known as "SQL Fairy") installed.
1265 To create a set of database-specific .sql files for the above schema:
1267 my $schema = My::Schema->connect($dsn);
1268 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1273 By default this will create schema files in the current directory, for
1274 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1276 To create a new database using the schema:
1278 my $schema = My::Schema->connect($dsn);
1279 $schema->deploy({ add_drop_tables => 1});
1281 To import created .sql files using the mysql client:
1283 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1285 To create C<ALTER TABLE> conversion scripts to update a database to a
1286 newer version of your schema at a later point, first set a new
1287 C<$VERSION> in your Schema file, then:
1289 my $schema = My::Schema->connect($dsn);
1290 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1296 This will produce new database-specific .sql files for the new version
1297 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1298 requires that the files for 0.1 as created above are available in the
1299 given directory to diff against.
1301 =head2 Select from dual
1303 Dummy tables are needed by some databases to allow calling functions
1304 or expressions that aren't based on table content, for examples of how
1305 this applies to various database types, see:
1306 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1308 Note: If you're using Oracles dual table don't B<ever> do anything
1309 other than a select, if you CRUD on your dual table you *will* break
1312 Make a table class as you would for any other table
1314 package MyAppDB::Dual;
1317 use base 'DBIx::Class';
1318 __PACKAGE__->load_components("Core");
1319 __PACKAGE__->table("Dual");
1320 __PACKAGE__->add_columns(
1322 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1325 Once you've loaded your table class select from it using C<select>
1326 and C<as> instead of C<columns>
1328 my $rs = $schema->resultset('Dual')->search(undef,
1329 { select => [ 'sydate' ],
1334 All you have to do now is be careful how you access your resultset, the below
1335 will not work because there is no column called 'now' in the Dual table class
1337 while (my $dual = $rs->next) {
1338 print $dual->now."\n";
1340 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1342 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1343 your Dual class for whatever you wanted to select from dual, but that's just
1344 silly, instead use C<get_column>
1346 while (my $dual = $rs->next) {
1347 print $dual->get_column('now')."\n";
1352 my $cursor = $rs->cursor;
1353 while (my @vals = $cursor->next) {
1354 print $vals[0]."\n";
1357 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1358 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1359 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1360 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1361 L<SQL::Translator> to not create table dual:
1364 add_drop_table => 1,
1365 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1367 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1369 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1371 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1372 while ( my $dual = $rs->next ) {
1373 print $dual->{now}."\n";
1376 Here are some example C<select> conditions to illustrate the different syntax
1377 you could use for doing stuff like
1378 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1380 # get a sequence value
1381 select => [ 'A_SEQ.nextval' ],
1383 # get create table sql
1384 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1386 # get a random num between 0 and 100
1387 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1390 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1393 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1395 # which day of the week were you born on?
1396 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1398 # select 16 rows from dual
1399 select => [ "'hello'" ],
1401 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1405 =head2 Adding Indexes And Functions To Your SQL
1407 Often you will want indexes on columns on your table to speed up searching. To
1408 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1409 class (refer to the advanced
1410 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1411 to share a hook between multiple sources):
1413 package My::Schema::Result::Artist;
1415 __PACKAGE__->table('artist');
1416 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1418 sub sqlt_deploy_hook {
1419 my ($self, $sqlt_table) = @_;
1421 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1426 Sometimes you might want to change the index depending on the type of the
1427 database for which SQL is being generated:
1429 my ($db_type = $sqlt_table->schema->translator->producer_type)
1430 =~ s/^SQL::Translator::Producer:://;
1432 You can also add hooks to the schema level to stop certain tables being
1439 sub sqlt_deploy_hook {
1440 my ($self, $sqlt_schema) = @_;
1442 $sqlt_schema->drop_table('table_name');
1445 You could also add views, procedures or triggers to the output using
1446 L<SQL::Translator::Schema/add_view>,
1447 L<SQL::Translator::Schema/add_procedure> or
1448 L<SQL::Translator::Schema/add_trigger>.
1451 =head2 Schema versioning
1453 The following example shows simplistically how you might use DBIx::Class to
1454 deploy versioned schemas to your customers. The basic process is as follows:
1460 Create a DBIx::Class schema
1472 Modify schema to change functionality
1476 Deploy update to customers
1480 B<Create a DBIx::Class schema>
1482 This can either be done manually, or generated from an existing database as
1483 described under L</Creating Schemas From An Existing Database>
1487 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1489 B<Deploy to customers>
1491 There are several ways you could deploy your schema. These are probably
1492 beyond the scope of this recipe, but might include:
1498 Require customer to apply manually using their RDBMS.
1502 Package along with your app, making database dump/schema update/tests
1503 all part of your install.
1507 B<Modify the schema to change functionality>
1509 As your application evolves, it may be necessary to modify your schema
1510 to change functionality. Once the changes are made to your schema in
1511 DBIx::Class, export the modified schema and the conversion scripts as
1512 in L</Creating DDL SQL>.
1514 B<Deploy update to customers>
1516 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1517 Schema class. This will add a new table to your database called
1518 C<dbix_class_schema_vesion> which will keep track of which version is installed
1519 and warn if the user trys to run a newer schema version than the
1520 database thinks it has.
1522 Alternatively, you can send the conversion sql scripts to your
1525 =head2 Setting quoting for the generated SQL
1527 If the database contains column names with spaces and/or reserved words, they
1528 need to be quoted in the SQL queries. This is done using:
1530 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1531 $schema->storage->sql_maker->name_sep('.');
1533 The first sets the quote characters. Either a pair of matching
1534 brackets, or a C<"> or C<'>:
1536 $schema->storage->sql_maker->quote_char('"');
1538 Check the documentation of your database for the correct quote
1539 characters to use. C<name_sep> needs to be set to allow the SQL
1540 generator to put the quotes the correct place.
1542 In most cases you should set these as part of the arguments passed to
1543 L<DBIx::Class::Schema/connect>:
1545 my $schema = My::Schema->connect(
1555 In some cases, quoting will be required for all users of a schema. To enforce
1556 this, you can also overload the C<connection> method for your schema class:
1560 my $rv = $self->next::method( @_ );
1561 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1562 $rv->storage->sql_maker->name_sep('.');
1566 =head2 Setting limit dialect for SQL::Abstract::Limit
1568 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1569 the remote SQL server by looking at the database handle. This is a
1570 common problem when using the DBD::JDBC, since the DBD-driver only
1571 know that in has a Java-driver available, not which JDBC driver the
1572 Java component has loaded. This specifically sets the limit_dialect
1573 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1576 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1578 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1579 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1581 The limit dialect can also be set at connect time by specifying a
1582 C<limit_dialect> key in the final hash as shown above.
1584 =head2 Working with PostgreSQL array types
1586 You can also assign values to PostgreSQL array columns by passing array
1587 references in the C<\%columns> (C<\%vals>) hashref of the
1588 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1591 $resultset->create({
1592 numbers => [1, 2, 3]
1597 numbers => [1, 2, 3]
1604 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1605 methods) you cannot directly use array references (since this is interpreted as
1606 a list of values to be C<OR>ed), but you can use the following syntax to force
1607 passing them as bind values:
1611 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1615 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1616 placeholders and bind values (subqueries)> for more explanation. Note that
1617 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1618 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1619 arrayrefs together with the column name, like this: C<< [column_name => value]
1622 =head1 BOOTSTRAPPING/MIGRATING
1624 =head2 Easy migration from class-based to schema-based setup
1626 You want to start using the schema-based approach to L<DBIx::Class>
1627 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1628 of existing classes that you don't want to move by hand. Try this nifty script
1632 use SQL::Translator;
1634 my $schema = MyDB->schema_instance;
1636 my $translator = SQL::Translator->new(
1637 debug => $debug || 0,
1638 trace => $trace || 0,
1639 no_comments => $no_comments || 0,
1640 show_warnings => $show_warnings || 0,
1641 add_drop_table => $add_drop_table || 0,
1642 validate => $validate || 0,
1644 'DBIx::Schema' => $schema,
1647 'prefix' => 'My::Schema',
1651 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1652 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1654 my $output = $translator->translate(@args) or die
1655 "Error: " . $translator->error;
1659 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1660 namespace, which is currently left as an exercise for the reader.
1662 =head1 OVERLOADING METHODS
1664 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1665 method calls, useful for things like default values and triggers. You have to
1666 use calls to C<next::method> to overload methods. More information on using
1667 L<Class::C3> with L<DBIx::Class> can be found in
1668 L<DBIx::Class::Manual::Component>.
1670 =head2 Setting default values for a row
1672 It's as simple as overriding the C<new> method. Note the use of
1676 my ( $class, $attrs ) = @_;
1678 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1680 my $new = $class->next::method($attrs);
1685 For more information about C<next::method>, look in the L<Class::C3>
1686 documentation. See also L<DBIx::Class::Manual::Component> for more
1687 ways to write your own base classes to do this.
1689 People looking for ways to do "triggers" with DBIx::Class are probably
1690 just looking for this.
1692 =head2 Changing one field whenever another changes
1694 For example, say that you have three columns, C<id>, C<number>, and
1695 C<squared>. You would like to make changes to C<number> and have
1696 C<squared> be automagically set to the value of C<number> squared.
1697 You can accomplish this by overriding C<store_column>:
1700 my ( $self, $name, $value ) = @_;
1701 if ($name eq 'number') {
1702 $self->squared($value * $value);
1704 $self->next::method($name, $value);
1707 Note that the hard work is done by the call to C<next::method>, which
1708 redispatches your call to store_column in the superclass(es).
1710 =head2 Automatically creating related objects
1712 You might have a class C<Artist> which has many C<CD>s. Further, you
1713 want to create a C<CD> object every time you insert an C<Artist> object.
1714 You can accomplish this by overriding C<insert> on your objects:
1717 my ( $self, @args ) = @_;
1718 $self->next::method(@args);
1719 $self->cds->new({})->fill_from_artist($self)->insert;
1723 where C<fill_from_artist> is a method you specify in C<CD> which sets
1724 values in C<CD> based on the data in the C<Artist> object you pass in.
1726 =head2 Wrapping/overloading a column accessor
1730 Say you have a table "Camera" and want to associate a description
1731 with each camera. For most cameras, you'll be able to generate the description from
1732 the other columns. However, in a few special cases you may want to associate a
1733 custom description with a camera.
1737 In your database schema, define a description field in the "Camera" table that
1738 can contain text and null values.
1740 In DBIC, we'll overload the column accessor to provide a sane default if no
1741 custom description is defined. The accessor will either return or generate the
1742 description, depending on whether the field is null or not.
1744 First, in your "Camera" schema class, define the description field as follows:
1746 __PACKAGE__->add_columns(description => { accessor => '_description' });
1748 Next, we'll define the accessor-wrapper subroutine:
1753 # If there is an update to the column, we'll let the original accessor
1755 return $self->_description(@_) if @_;
1757 # Fetch the column value.
1758 my $description = $self->_description;
1760 # If there's something in the description field, then just return that.
1761 return $description if defined $description && length $descripton;
1763 # Otherwise, generate a description.
1764 return $self->generate_description;
1767 =head1 DEBUGGING AND PROFILING
1769 =head2 DBIx::Class objects with Data::Dumper
1771 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1772 be hard to find the pertinent data in all the data it can generate.
1773 Specifically, if one naively tries to use it like so,
1777 my $cd = $schema->resultset('CD')->find(1);
1780 several pages worth of data from the CD object's schema and result source will
1781 be dumped to the screen. Since usually one is only interested in a few column
1782 values of the object, this is not very helpful.
1784 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1785 it. Simply define a hook that L<Data::Dumper> will call on the object before
1786 dumping it. For example,
1793 result_source => undef,
1801 local $Data::Dumper::Freezer = '_dumper_hook';
1803 my $cd = $schema->resultset('CD')->find(1);
1805 # dumps $cd without its ResultSource
1807 If the structure of your schema is such that there is a common base class for
1808 all your table classes, simply put a method similar to C<_dumper_hook> in the
1809 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1810 will automagically clean up your data before printing it. See
1811 L<Data::Dumper/EXAMPLES> for more information.
1815 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1816 executed as well as notifications of query completion and transaction
1817 begin/commit. If you'd like to profile the SQL you can subclass the
1818 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1821 package My::Profiler;
1824 use base 'DBIx::Class::Storage::Statistics';
1826 use Time::HiRes qw(time);
1835 $self->print("Executing $sql: ".join(', ', @params)."\n");
1844 my $elapsed = sprintf("%0.4f", time() - $start);
1845 $self->print("Execution took $elapsed seconds.\n");
1851 You can then install that class as the debugging object:
1853 __PACKAGE__->storage->debugobj(new My::Profiler());
1854 __PACKAGE__->storage->debug(1);
1856 A more complicated example might involve storing each execution of SQL in an
1864 my $elapsed = time() - $start;
1865 push(@{ $calls{$sql} }, {
1871 You could then create average, high and low execution times for an SQL
1872 statement and dig down to see if certain parameters cause aberrant behavior.
1873 You might want to check out L<DBIx::Class::QueryLog> as well.
1875 =head1 STARTUP SPEED
1877 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1878 as the ORM loads all the relevant classes. This section examines
1879 techniques for reducing the startup delay.
1881 These tips are are listed in order of decreasing effectiveness - so the
1882 first tip, if applicable, should have the greatest effect on your
1885 =head2 Statically Define Your Schema
1888 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1889 classes dynamically based on the database schema then there will be a
1890 significant startup delay.
1892 For production use a statically defined schema (which can be generated
1893 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1894 the database schema once - see
1895 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1896 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1897 details on creating static schemas from a database).
1899 =head2 Move Common Startup into a Base Class
1901 Typically L<DBIx::Class> result classes start off with
1903 use base qw/DBIx::Class/;
1904 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1906 If this preamble is moved into a common base class:-
1910 use base qw/DBIx::Class/;
1911 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1914 and each result class then uses this as a base:-
1916 use base qw/MyDBICbase/;
1918 then the load_components is only performed once, which can result in a
1919 considerable startup speedup for schemas with many classes.
1921 =head2 Explicitly List Schema Result Classes
1923 The schema class will normally contain
1925 __PACKAGE__->load_classes();
1927 to load the result classes. This will use L<Module::Find|Module::Find>
1928 to find and load the appropriate modules. Explicitly defining the
1929 classes you wish to load will remove the overhead of
1930 L<Module::Find|Module::Find> and the related directory operations:
1932 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1934 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1935 syntax to load the appropriate classes there is not a direct alternative
1936 avoiding L<Module::Find|Module::Find>.
1940 =head2 Cached statements
1942 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
1943 This is normally a good idea, but if too many statements are cached, the database may use too much
1944 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
1945 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
1947 # print all currently cached prepared statements
1948 print for keys %{$schema->storage->dbh->{CachedKids}};
1949 # get a count of currently cached prepared statements
1950 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
1952 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
1955 my $kids = $schema->storage->dbh->{CachedKids};
1956 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
1958 But what you probably want is to expire unused statements and not those that are used frequently.
1959 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
1963 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
1964 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },