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, # does NOT work
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 not a
413 good idea since it requires a scan of the entire table. (Unless your RDBMS
414 supports indexes on expressions - including return values of functions -, and
415 you create an index on the return value of the function in question.) However,
416 it can be accomplished with C<DBIx::Class> when necessary.
418 If you do not have quoting on, simply include the function in your search
419 specification as you would any column:
421 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
423 With quoting on, or for a more portable solution, use literal SQL values with
426 $rs->search(\[ 'YEAR(date_of_birth)', [ dummy => 1979 ] ]);
429 # SELECT * FROM employee WHERE YEAR(date_of_birth) = ?
433 -nest => \[ 'YEAR(date_of_birth)', [ dummy => 1979 ] ],
437 # SELECT * FROM employee WHERE name = ? AND YEAR(date_of_birth) = ?
439 See also L<SQL::Abstract/Literal SQL with placeholders and bind values
442 =head1 JOINS AND PREFETCHING
444 =head2 Using joins and prefetch
446 You can use the C<join> attribute to allow searching on, or sorting your
447 results by, one or more columns in a related table.
449 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
451 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
453 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
455 my $rs = $schema->resultset('CD')->search(
457 'artists.name' => 'Bob Marley'
460 join => 'artists', # join the artist table
465 # SELECT cd.* FROM cd
466 # JOIN artist ON cd.artist = artist.id
467 # WHERE artist.name = 'Bob Marley'
469 In that example both the join, and the condition use the relationship name rather than the table name
470 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
472 If required, you can now sort on any column in the related tables by including
473 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
475 my $rs = $schema->resultset('CD')->search(
477 'artists.name' => 'Bob Marley'
481 order_by => [qw/ artists.name /]
486 # SELECT cd.* FROM cd
487 # JOIN artist ON cd.artist = artist.id
488 # WHERE artist.name = 'Bob Marley'
489 # ORDER BY artist.name
491 Note that the C<join> attribute should only be used when you need to search or
492 sort using columns in a related table. Joining related tables when you only
493 need columns from the main table will make performance worse!
495 Now let's say you want to display a list of CDs, each with the name of the
496 artist. The following will work fine:
498 while (my $cd = $rs->next) {
499 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
502 There is a problem however. We have searched both the C<cd> and C<artist> tables
503 in our main query, but we have only returned data from the C<cd> table. To get
504 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
507 SELECT artist.* FROM artist WHERE artist.id = ?
509 A statement like the one above will run for each and every CD returned by our
510 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
513 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
514 This allows you to fetch results from related tables in advance:
516 my $rs = $schema->resultset('CD')->search(
518 'artists.name' => 'Bob Marley'
522 order_by => [qw/ artists.name /],
523 prefetch => 'artists' # return artist data too!
527 # Equivalent SQL (note SELECT from both "cd" and "artist"):
528 # SELECT cd.*, artist.* FROM cd
529 # JOIN artist ON cd.artist = artist.id
530 # WHERE artist.name = 'Bob Marley'
531 # ORDER BY artist.name
533 The code to print the CD list remains the same:
535 while (my $cd = $rs->next) {
536 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
539 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
540 so no additional SQL statements are executed. You now have a much more
543 Also note that C<prefetch> should only be used when you know you will
544 definitely use data from a related table. Pre-fetching related tables when you
545 only need columns from the main table will make performance worse!
547 =head2 Multiple joins
549 In the examples above, the C<join> attribute was a scalar. If you
550 pass an array reference instead, you can join to multiple tables. In
551 this example, we want to limit the search further, using
554 # Relationships defined elsewhere:
555 # CD->belongs_to('artist' => 'Artist');
556 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
557 my $rs = $schema->resultset('CD')->search(
559 'artist.name' => 'Bob Marley'
560 'liner_notes.notes' => { 'like', '%some text%' },
563 join => [qw/ artist liner_notes /],
564 order_by => [qw/ artist.name /],
569 # SELECT cd.*, artist.*, liner_notes.* FROM cd
570 # JOIN artist ON cd.artist = artist.id
571 # JOIN liner_notes ON cd.id = liner_notes.cd
572 # WHERE artist.name = 'Bob Marley'
573 # ORDER BY artist.name
575 =head2 Multi-step joins
577 Sometimes you want to join more than one relationship deep. In this example,
578 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
579 contain a specific string:
581 # Relationships defined elsewhere:
582 # Artist->has_many('cds' => 'CD', 'artist');
583 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
585 my $rs = $schema->resultset('Artist')->search(
587 'liner_notes.notes' => { 'like', '%some text%' },
591 'cds' => 'liner_notes'
597 # SELECT artist.* FROM artist
598 # LEFT JOIN cd ON artist.id = cd.artist
599 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
600 # WHERE liner_notes.notes LIKE '%some text%'
602 Joins can be nested to an arbitrary level. So if we decide later that we
603 want to reduce the number of Artists returned based on who wrote the liner
606 # Relationship defined elsewhere:
607 # LinerNotes->belongs_to('author' => 'Person');
609 my $rs = $schema->resultset('Artist')->search(
611 'liner_notes.notes' => { 'like', '%some text%' },
612 'author.name' => 'A. Writer'
617 'liner_notes' => 'author'
624 # SELECT artist.* FROM artist
625 # LEFT JOIN cd ON artist.id = cd.artist
626 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
627 # LEFT JOIN author ON author.id = liner_notes.author
628 # WHERE liner_notes.notes LIKE '%some text%'
629 # AND author.name = 'A. Writer'
631 =head2 Multi-step and multiple joins
633 With various combinations of array and hash references, you can join
634 tables in any combination you desire. For example, to join Artist to
635 CD and Concert, and join CD to LinerNotes:
637 # Relationships defined elsewhere:
638 # Artist->has_many('concerts' => 'Concert', 'artist');
640 my $rs = $schema->resultset('Artist')->search(
653 # SELECT artist.* FROM artist
654 # LEFT JOIN cd ON artist.id = cd.artist
655 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
656 # LEFT JOIN concert ON artist.id = concert.artist
658 =head2 Multi-step prefetch
660 C<prefetch> can be nested more than one relationship
661 deep using the same syntax as a multi-step join:
663 my $rs = $schema->resultset('Tag')->search(
673 # SELECT tag.*, cd.*, artist.* FROM tag
674 # JOIN cd ON tag.cd = cd.id
675 # JOIN artist ON cd.artist = artist.id
677 Now accessing our C<cd> and C<artist> relationships does not need additional
680 my $tag = $rs->first;
681 print $tag->cd->artist->name;
683 =head1 ROW-LEVEL OPERATIONS
685 =head2 Retrieving a row object's Schema
687 It is possible to get a Schema object from a row object like so:
689 my $schema = $cd->result_source->schema;
690 # use the schema as normal:
691 my $artist_rs = $schema->resultset('Artist');
693 This can be useful when you don't want to pass around a Schema object to every
696 =head2 Getting the value of the primary key for the last database insert
698 AKA getting last_insert_id
700 Thanks to the core component PK::Auto, this is straightforward:
702 my $foo = $rs->create(\%blah);
704 my $id = $foo->id; # foo->my_primary_key_field will also work.
706 If you are not using autoincrementing primary keys, this will probably
707 not work, but then you already know the value of the last primary key anyway.
709 =head2 Stringification
711 Employ the standard stringification technique by using the L<overload>
714 To make an object stringify itself as a single column, use something
715 like this (replace C<name> with the column/method of your choice):
717 use overload '""' => sub { shift->name}, fallback => 1;
719 For more complex stringification, you can use an anonymous subroutine:
721 use overload '""' => sub { $_[0]->name . ", " .
722 $_[0]->address }, fallback => 1;
724 =head3 Stringification Example
726 Suppose we have two tables: C<Product> and C<Category>. The table
729 Product(id, Description, category)
730 Category(id, Description)
732 C<category> is a foreign key into the Category table.
734 If you have a Product object C<$obj> and write something like
738 things will not work as expected.
740 To obtain, for example, the category description, you should add this
741 method to the class defining the Category table:
743 use overload "" => sub {
746 return $self->Description;
749 =head2 Want to know if find_or_create found or created a row?
751 Just use C<find_or_new> instead, then check C<in_storage>:
753 my $obj = $rs->find_or_new({ blah => 'blarg' });
754 unless ($obj->in_storage) {
756 # do whatever else you wanted if it was a new row
759 =head2 Static sub-classing DBIx::Class result classes
761 AKA adding additional relationships/methods/etc. to a model for a
762 specific usage of the (shared) model.
766 package My::App::Schema;
768 use base DBIx::Class::Schema;
770 # load subclassed classes from My::App::Schema::Result/ResultSet
771 __PACKAGE__->load_namespaces;
773 # load classes from shared model
775 'My::Shared::Model::Result' => [qw/
782 B<Result-Subclass definition>
784 package My::App::Schema::Result::Baz;
788 use base My::Shared::Model::Result::Baz;
790 # WARNING: Make sure you call table() again in your subclass,
791 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
792 # and the class name is not correctly registered as a source
793 __PACKAGE__->table('baz');
795 sub additional_method {
796 return "I'm an additional method only needed by this app";
801 =head2 Dynamic Sub-classing DBIx::Class proxy classes
803 AKA multi-class object inflation from one table
805 L<DBIx::Class> classes are proxy classes, therefore some different
806 techniques need to be employed for more than basic subclassing. In
807 this example we have a single user table that carries a boolean bit
808 for admin. We would like like to give the admin users
809 objects (L<DBIx::Class::Row>) the same methods as a regular user but
810 also special admin only methods. It doesn't make sense to create two
811 seperate proxy-class files for this. We would be copying all the user
812 methods into the Admin class. There is a cleaner way to accomplish
815 Overriding the C<inflate_result> method within the User proxy-class
816 gives us the effect we want. This method is called by
817 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
818 grab the object being returned, inspect the values we are looking for,
819 bless it if it's an admin object, and then return it. See the example
826 use base qw/DBIx::Class::Schema/;
828 __PACKAGE__->load_namespaces;
833 B<Proxy-Class definitions>
835 package My::Schema::Result::User;
839 use base qw/DBIx::Class/;
841 ### Define what our admin class is, for ensure_class_loaded()
842 my $admin_class = __PACKAGE__ . '::Admin';
844 __PACKAGE__->load_components(qw/Core/);
846 __PACKAGE__->table('users');
848 __PACKAGE__->add_columns(qw/user_id email password
849 firstname lastname active
852 __PACKAGE__->set_primary_key('user_id');
856 my $ret = $self->next::method(@_);
857 if( $ret->admin ) {### If this is an admin, rebless for extra functions
858 $self->ensure_class_loaded( $admin_class );
859 bless $ret, $admin_class;
865 print "I am a regular user.\n";
872 package My::Schema::Result::User::Admin;
876 use base qw/My::Schema::Result::User/;
878 # This line is important
879 __PACKAGE__->table('users');
883 print "I am an admin.\n";
889 print "I am doing admin stuff\n";
901 my $user_data = { email => 'someguy@place.com',
905 my $admin_data = { email => 'someadmin@adminplace.com',
909 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
911 $schema->resultset('User')->create( $user_data );
912 $schema->resultset('User')->create( $admin_data );
914 ### Now we search for them
915 my $user = $schema->resultset('User')->single( $user_data );
916 my $admin = $schema->resultset('User')->single( $admin_data );
918 print ref $user, "\n";
919 print ref $admin, "\n";
921 print $user->password , "\n"; # pass1
922 print $admin->password , "\n";# pass2; inherited from User
923 print $user->hello , "\n";# I am a regular user.
924 print $admin->hello, "\n";# I am an admin.
926 ### The statement below will NOT print
927 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
928 ### The statement below will print
929 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
931 Alternatively you can use L<DBIx::Class::DynamicSubclass> that implements
932 exactly the above functionality.
934 =head2 Skip row object creation for faster results
936 DBIx::Class is not built for speed, it's built for convenience and
937 ease of use, but sometimes you just need to get the data, and skip the
940 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
942 my $rs = $schema->resultset('CD');
944 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
946 my $hash_ref = $rs->find(1);
950 Beware, changing the Result class using
951 L<DBIx::Class::ResultSet/result_class> will replace any existing class
952 completely including any special components loaded using
953 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
955 =head2 Get raw data for blindingly fast results
957 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
958 above is not fast enough for you, you can use a DBIx::Class to return values
959 exactly as they come out of the database with none of the convenience methods
962 This is used like so:
964 my $cursor = $rs->cursor
965 while (my @vals = $cursor->next) {
966 # use $val[0..n] here
969 You will need to map the array offsets to particular columns (you can
970 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
972 =head1 RESULTSET OPERATIONS
974 =head2 Getting Schema from a ResultSet
976 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
978 $rs->result_source->schema
980 =head2 Getting Columns Of Data
984 If you want to find the sum of a particular column there are several
985 ways, the obvious one is to use search:
987 my $rs = $schema->resultset('Items')->search(
990 select => [ { sum => 'Cost' } ],
991 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
994 my $tc = $rs->first->get_column('total_cost');
996 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
997 returned when you ask the C<ResultSet> for a column using
1000 my $cost = $schema->resultset('Items')->get_column('Cost');
1001 my $tc = $cost->sum;
1003 With this you can also do:
1005 my $minvalue = $cost->min;
1006 my $maxvalue = $cost->max;
1008 Or just iterate through the values of this column only:
1010 while ( my $c = $cost->next ) {
1014 foreach my $c ($cost->all) {
1018 C<ResultSetColumn> only has a limited number of built-in functions. If
1019 you need one that it doesn't have, then you can use the C<func> method
1022 my $avg = $cost->func('AVERAGE');
1024 This will cause the following SQL statement to be run:
1026 SELECT AVERAGE(Cost) FROM Items me
1028 Which will of course only work if your database supports this function.
1029 See L<DBIx::Class::ResultSetColumn> for more documentation.
1031 =head2 Creating a result set from a set of rows
1033 Sometimes you have a (set of) row objects that you want to put into a
1034 resultset without the need to hit the DB again. You can do that by using the
1035 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1037 my @uploadable_groups;
1038 while (my $group = $groups->next) {
1039 if ($group->can_upload($self)) {
1040 push @uploadable_groups, $group;
1043 my $new_rs = $self->result_source->resultset;
1044 $new_rs->set_cache(\@uploadable_groups);
1048 =head1 USING RELATIONSHIPS
1050 =head2 Create a new row in a related table
1052 my $author = $book->create_related('author', { name => 'Fred'});
1054 =head2 Search in a related table
1056 Only searches for books named 'Titanic' by the author in $author.
1058 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1060 =head2 Delete data in a related table
1062 Deletes only the book named Titanic by the author in $author.
1064 $author->delete_related('books', { name => 'Titanic' });
1066 =head2 Ordering a relationship result set
1068 If you always want a relation to be ordered, you can specify this when you
1069 create the relationship.
1071 To order C<< $book->pages >> by descending page_number, create the relation
1074 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => { -desc => 'page_number'} } );
1076 =head2 Filtering a relationship result set
1078 If you want to get a filtered result set, you can just add add to $attr as follows:
1080 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1082 =head2 Many-to-many relationships
1084 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1087 use base 'DBIx::Class';
1088 __PACKAGE__->load_components('Core');
1089 __PACKAGE__->table('user');
1090 __PACKAGE__->add_columns(qw/id name/);
1091 __PACKAGE__->set_primary_key('id');
1092 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1093 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1095 package My::UserAddress;
1096 use base 'DBIx::Class';
1097 __PACKAGE__->load_components('Core');
1098 __PACKAGE__->table('user_address');
1099 __PACKAGE__->add_columns(qw/user address/);
1100 __PACKAGE__->set_primary_key(qw/user address/);
1101 __PACKAGE__->belongs_to('user' => 'My::User');
1102 __PACKAGE__->belongs_to('address' => 'My::Address');
1104 package My::Address;
1105 use base 'DBIx::Class';
1106 __PACKAGE__->load_components('Core');
1107 __PACKAGE__->table('address');
1108 __PACKAGE__->add_columns(qw/id street town area_code country/);
1109 __PACKAGE__->set_primary_key('id');
1110 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1111 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1113 $rs = $user->addresses(); # get all addresses for a user
1114 $rs = $address->users(); # get all users for an address
1116 =head2 Relationships across DB schemas
1118 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1119 is easy as long as the schemas themselves are all accessible via the same DBI
1120 connection. In most cases, this means that they are on the same database host
1121 as each other and your connecting database user has the proper permissions to them.
1123 To accomplish this one only needs to specify the DB schema name in the table
1124 declaration, like so...
1126 package MyDatabase::Main::Artist;
1127 use base qw/DBIx::Class/;
1128 __PACKAGE__->load_components(qw/PK::Auto Core/);
1130 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1132 __PACKAGE__->add_columns(qw/ artist_id name /);
1133 __PACKAGE__->set_primary_key('artist_id');
1134 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1138 Whatever string you specify there will be used to build the "FROM" clause in SQL
1141 The big drawback to this is you now have DB schema names hardcoded in your
1142 class files. This becomes especially troublesome if you have multiple instances
1143 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1144 the DB schemas are named based on the environment (e.g. database1_dev).
1146 However, one can dynamically "map" to the proper DB schema by overriding the
1147 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1148 building a renaming facility, like so:
1150 package MyDatabase::Schema;
1153 extends 'DBIx::Class::Schema';
1155 around connection => sub {
1156 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1158 my $postfix = delete $attr->{schema_name_postfix};
1163 $self->append_db_name($postfix);
1167 sub append_db_name {
1168 my ( $self, $postfix ) = @_;
1172 { $_->name =~ /^\w+\./mx }
1174 { $self->source($_) }
1177 foreach my $source (@sources_with_db) {
1178 my $name = $source->name;
1179 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1181 $source->name($name);
1187 By overridding the L<connection|DBIx::Class::Schama/connection>
1188 method and extracting a custom option from the provided \%attr hashref one can
1189 then simply iterate over all the Schema's ResultSources, renaming them as
1192 To use this facility, simply add or modify the \%attr hashref that is passed to
1193 L<connection|DBIx::Class::Schama/connect>, as follows:
1196 = MyDatabase::Schema->connect(
1201 schema_name_postfix => '_dev'
1202 # ... Other options as desired ...
1205 Obviously, one could accomplish even more advanced mapping via a hash map or a
1210 As of version 0.04001, there is improved transaction support in
1211 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1212 example of the recommended way to use it:
1214 my $genus = $schema->resultset('Genus')->find(12);
1216 my $coderef2 = sub {
1221 my $coderef1 = sub {
1222 $genus->add_to_species({ name => 'troglodyte' });
1225 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1226 return $genus->species;
1231 $rs = $schema->txn_do($coderef1);
1234 if ($@) { # Transaction failed
1235 die "the sky is falling!" #
1236 if ($@ =~ /Rollback failed/); # Rollback failed
1238 deal_with_failed_transaction();
1241 Nested transactions will work as expected. That is, only the outermost
1242 transaction will actually issue a commit to the $dbh, and a rollback
1243 at any level of any transaction will cause the entire nested
1244 transaction to fail. Support for savepoints and for true nested
1245 transactions (for databases that support them) will hopefully be added
1250 =head2 Creating Schemas From An Existing Database
1252 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1253 L<DBIx::Class::Schema> and associated sources by examining the database.
1255 The recommend way of achieving this is to use the
1256 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1258 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1259 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1261 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1262 source definitions for all the tables found in the C<foo> database.
1264 =head2 Creating DDL SQL
1266 The following functionality requires you to have L<SQL::Translator>
1267 (also known as "SQL Fairy") installed.
1269 To create a set of database-specific .sql files for the above schema:
1271 my $schema = My::Schema->connect($dsn);
1272 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1277 By default this will create schema files in the current directory, for
1278 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1280 To create a new database using the schema:
1282 my $schema = My::Schema->connect($dsn);
1283 $schema->deploy({ add_drop_tables => 1});
1285 To import created .sql files using the mysql client:
1287 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1289 To create C<ALTER TABLE> conversion scripts to update a database to a
1290 newer version of your schema at a later point, first set a new
1291 C<$VERSION> in your Schema file, then:
1293 my $schema = My::Schema->connect($dsn);
1294 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1300 This will produce new database-specific .sql files for the new version
1301 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1302 requires that the files for 0.1 as created above are available in the
1303 given directory to diff against.
1305 =head2 Select from dual
1307 Dummy tables are needed by some databases to allow calling functions
1308 or expressions that aren't based on table content, for examples of how
1309 this applies to various database types, see:
1310 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1312 Note: If you're using Oracles dual table don't B<ever> do anything
1313 other than a select, if you CRUD on your dual table you *will* break
1316 Make a table class as you would for any other table
1318 package MyAppDB::Dual;
1321 use base 'DBIx::Class';
1322 __PACKAGE__->load_components("Core");
1323 __PACKAGE__->table("Dual");
1324 __PACKAGE__->add_columns(
1326 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1329 Once you've loaded your table class select from it using C<select>
1330 and C<as> instead of C<columns>
1332 my $rs = $schema->resultset('Dual')->search(undef,
1333 { select => [ 'sydate' ],
1338 All you have to do now is be careful how you access your resultset, the below
1339 will not work because there is no column called 'now' in the Dual table class
1341 while (my $dual = $rs->next) {
1342 print $dual->now."\n";
1344 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1346 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1347 your Dual class for whatever you wanted to select from dual, but that's just
1348 silly, instead use C<get_column>
1350 while (my $dual = $rs->next) {
1351 print $dual->get_column('now')."\n";
1356 my $cursor = $rs->cursor;
1357 while (my @vals = $cursor->next) {
1358 print $vals[0]."\n";
1361 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1362 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1363 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1364 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1365 L<SQL::Translator> to not create table dual:
1368 add_drop_table => 1,
1369 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1371 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1373 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1375 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1376 while ( my $dual = $rs->next ) {
1377 print $dual->{now}."\n";
1380 Here are some example C<select> conditions to illustrate the different syntax
1381 you could use for doing stuff like
1382 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1384 # get a sequence value
1385 select => [ 'A_SEQ.nextval' ],
1387 # get create table sql
1388 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1390 # get a random num between 0 and 100
1391 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1394 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1397 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1399 # which day of the week were you born on?
1400 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1402 # select 16 rows from dual
1403 select => [ "'hello'" ],
1405 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1409 =head2 Adding Indexes And Functions To Your SQL
1411 Often you will want indexes on columns on your table to speed up searching. To
1412 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1413 class (refer to the advanced
1414 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1415 to share a hook between multiple sources):
1417 package My::Schema::Result::Artist;
1419 __PACKAGE__->table('artist');
1420 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1422 sub sqlt_deploy_hook {
1423 my ($self, $sqlt_table) = @_;
1425 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1430 Sometimes you might want to change the index depending on the type of the
1431 database for which SQL is being generated:
1433 my ($db_type = $sqlt_table->schema->translator->producer_type)
1434 =~ s/^SQL::Translator::Producer:://;
1436 You can also add hooks to the schema level to stop certain tables being
1443 sub sqlt_deploy_hook {
1444 my ($self, $sqlt_schema) = @_;
1446 $sqlt_schema->drop_table('table_name');
1449 You could also add views, procedures or triggers to the output using
1450 L<SQL::Translator::Schema/add_view>,
1451 L<SQL::Translator::Schema/add_procedure> or
1452 L<SQL::Translator::Schema/add_trigger>.
1455 =head2 Schema versioning
1457 The following example shows simplistically how you might use DBIx::Class to
1458 deploy versioned schemas to your customers. The basic process is as follows:
1464 Create a DBIx::Class schema
1476 Modify schema to change functionality
1480 Deploy update to customers
1484 B<Create a DBIx::Class schema>
1486 This can either be done manually, or generated from an existing database as
1487 described under L</Creating Schemas From An Existing Database>
1491 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1493 B<Deploy to customers>
1495 There are several ways you could deploy your schema. These are probably
1496 beyond the scope of this recipe, but might include:
1502 Require customer to apply manually using their RDBMS.
1506 Package along with your app, making database dump/schema update/tests
1507 all part of your install.
1511 B<Modify the schema to change functionality>
1513 As your application evolves, it may be necessary to modify your schema
1514 to change functionality. Once the changes are made to your schema in
1515 DBIx::Class, export the modified schema and the conversion scripts as
1516 in L</Creating DDL SQL>.
1518 B<Deploy update to customers>
1520 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1521 Schema class. This will add a new table to your database called
1522 C<dbix_class_schema_vesion> which will keep track of which version is installed
1523 and warn if the user trys to run a newer schema version than the
1524 database thinks it has.
1526 Alternatively, you can send the conversion sql scripts to your
1529 =head2 Setting quoting for the generated SQL
1531 If the database contains column names with spaces and/or reserved words, they
1532 need to be quoted in the SQL queries. This is done using:
1534 $schema->storage->sql_maker->quote_char([ qw/[ ]/] );
1535 $schema->storage->sql_maker->name_sep('.');
1537 The first sets the quote characters. Either a pair of matching
1538 brackets, or a C<"> or C<'>:
1540 $schema->storage->sql_maker->quote_char('"');
1542 Check the documentation of your database for the correct quote
1543 characters to use. C<name_sep> needs to be set to allow the SQL
1544 generator to put the quotes the correct place.
1546 In most cases you should set these as part of the arguments passed to
1547 L<DBIx::Class::Schema/connect>:
1549 my $schema = My::Schema->connect(
1559 In some cases, quoting will be required for all users of a schema. To enforce
1560 this, you can also overload the C<connection> method for your schema class:
1564 my $rv = $self->next::method( @_ );
1565 $rv->storage->sql_maker->quote_char([ qw/[ ]/ ]);
1566 $rv->storage->sql_maker->name_sep('.');
1570 =head2 Setting limit dialect for SQL::Abstract::Limit
1572 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1573 the remote SQL server by looking at the database handle. This is a
1574 common problem when using the DBD::JDBC, since the DBD-driver only
1575 know that in has a Java-driver available, not which JDBC driver the
1576 Java component has loaded. This specifically sets the limit_dialect
1577 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1580 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1582 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1583 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1585 The limit dialect can also be set at connect time by specifying a
1586 C<limit_dialect> key in the final hash as shown above.
1588 =head2 Working with PostgreSQL array types
1590 You can also assign values to PostgreSQL array columns by passing array
1591 references in the C<\%columns> (C<\%vals>) hashref of the
1592 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1595 $resultset->create({
1596 numbers => [1, 2, 3]
1601 numbers => [1, 2, 3]
1608 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1609 methods) you cannot directly use array references (since this is interpreted as
1610 a list of values to be C<OR>ed), but you can use the following syntax to force
1611 passing them as bind values:
1615 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1619 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1620 placeholders and bind values (subqueries)> for more explanation. Note that
1621 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1622 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1623 arrayrefs together with the column name, like this: C<< [column_name => value]
1626 =head1 BOOTSTRAPPING/MIGRATING
1628 =head2 Easy migration from class-based to schema-based setup
1630 You want to start using the schema-based approach to L<DBIx::Class>
1631 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1632 of existing classes that you don't want to move by hand. Try this nifty script
1636 use SQL::Translator;
1638 my $schema = MyDB->schema_instance;
1640 my $translator = SQL::Translator->new(
1641 debug => $debug || 0,
1642 trace => $trace || 0,
1643 no_comments => $no_comments || 0,
1644 show_warnings => $show_warnings || 0,
1645 add_drop_table => $add_drop_table || 0,
1646 validate => $validate || 0,
1648 'DBIx::Schema' => $schema,
1651 'prefix' => 'My::Schema',
1655 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1656 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1658 my $output = $translator->translate(@args) or die
1659 "Error: " . $translator->error;
1663 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1664 namespace, which is currently left as an exercise for the reader.
1666 =head1 OVERLOADING METHODS
1668 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1669 method calls, useful for things like default values and triggers. You have to
1670 use calls to C<next::method> to overload methods. More information on using
1671 L<Class::C3> with L<DBIx::Class> can be found in
1672 L<DBIx::Class::Manual::Component>.
1674 =head2 Setting default values for a row
1676 It's as simple as overriding the C<new> method. Note the use of
1680 my ( $class, $attrs ) = @_;
1682 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1684 my $new = $class->next::method($attrs);
1689 For more information about C<next::method>, look in the L<Class::C3>
1690 documentation. See also L<DBIx::Class::Manual::Component> for more
1691 ways to write your own base classes to do this.
1693 People looking for ways to do "triggers" with DBIx::Class are probably
1694 just looking for this.
1696 =head2 Changing one field whenever another changes
1698 For example, say that you have three columns, C<id>, C<number>, and
1699 C<squared>. You would like to make changes to C<number> and have
1700 C<squared> be automagically set to the value of C<number> squared.
1701 You can accomplish this by overriding C<store_column>:
1704 my ( $self, $name, $value ) = @_;
1705 if ($name eq 'number') {
1706 $self->squared($value * $value);
1708 $self->next::method($name, $value);
1711 Note that the hard work is done by the call to C<next::method>, which
1712 redispatches your call to store_column in the superclass(es).
1714 =head2 Automatically creating related objects
1716 You might have a class C<Artist> which has many C<CD>s. Further, you
1717 want to create a C<CD> object every time you insert an C<Artist> object.
1718 You can accomplish this by overriding C<insert> on your objects:
1721 my ( $self, @args ) = @_;
1722 $self->next::method(@args);
1723 $self->cds->new({})->fill_from_artist($self)->insert;
1727 where C<fill_from_artist> is a method you specify in C<CD> which sets
1728 values in C<CD> based on the data in the C<Artist> object you pass in.
1730 =head2 Wrapping/overloading a column accessor
1734 Say you have a table "Camera" and want to associate a description
1735 with each camera. For most cameras, you'll be able to generate the description from
1736 the other columns. However, in a few special cases you may want to associate a
1737 custom description with a camera.
1741 In your database schema, define a description field in the "Camera" table that
1742 can contain text and null values.
1744 In DBIC, we'll overload the column accessor to provide a sane default if no
1745 custom description is defined. The accessor will either return or generate the
1746 description, depending on whether the field is null or not.
1748 First, in your "Camera" schema class, define the description field as follows:
1750 __PACKAGE__->add_columns(description => { accessor => '_description' });
1752 Next, we'll define the accessor-wrapper subroutine:
1757 # If there is an update to the column, we'll let the original accessor
1759 return $self->_description(@_) if @_;
1761 # Fetch the column value.
1762 my $description = $self->_description;
1764 # If there's something in the description field, then just return that.
1765 return $description if defined $description && length $descripton;
1767 # Otherwise, generate a description.
1768 return $self->generate_description;
1771 =head1 DEBUGGING AND PROFILING
1773 =head2 DBIx::Class objects with Data::Dumper
1775 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1776 be hard to find the pertinent data in all the data it can generate.
1777 Specifically, if one naively tries to use it like so,
1781 my $cd = $schema->resultset('CD')->find(1);
1784 several pages worth of data from the CD object's schema and result source will
1785 be dumped to the screen. Since usually one is only interested in a few column
1786 values of the object, this is not very helpful.
1788 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1789 it. Simply define a hook that L<Data::Dumper> will call on the object before
1790 dumping it. For example,
1797 result_source => undef,
1805 local $Data::Dumper::Freezer = '_dumper_hook';
1807 my $cd = $schema->resultset('CD')->find(1);
1809 # dumps $cd without its ResultSource
1811 If the structure of your schema is such that there is a common base class for
1812 all your table classes, simply put a method similar to C<_dumper_hook> in the
1813 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1814 will automagically clean up your data before printing it. See
1815 L<Data::Dumper/EXAMPLES> for more information.
1819 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1820 executed as well as notifications of query completion and transaction
1821 begin/commit. If you'd like to profile the SQL you can subclass the
1822 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1825 package My::Profiler;
1828 use base 'DBIx::Class::Storage::Statistics';
1830 use Time::HiRes qw(time);
1839 $self->print("Executing $sql: ".join(', ', @params)."\n");
1848 my $elapsed = sprintf("%0.4f", time() - $start);
1849 $self->print("Execution took $elapsed seconds.\n");
1855 You can then install that class as the debugging object:
1857 __PACKAGE__->storage->debugobj(new My::Profiler());
1858 __PACKAGE__->storage->debug(1);
1860 A more complicated example might involve storing each execution of SQL in an
1868 my $elapsed = time() - $start;
1869 push(@{ $calls{$sql} }, {
1875 You could then create average, high and low execution times for an SQL
1876 statement and dig down to see if certain parameters cause aberrant behavior.
1877 You might want to check out L<DBIx::Class::QueryLog> as well.
1879 =head1 STARTUP SPEED
1881 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1882 as the ORM loads all the relevant classes. This section examines
1883 techniques for reducing the startup delay.
1885 These tips are are listed in order of decreasing effectiveness - so the
1886 first tip, if applicable, should have the greatest effect on your
1889 =head2 Statically Define Your Schema
1892 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1893 classes dynamically based on the database schema then there will be a
1894 significant startup delay.
1896 For production use a statically defined schema (which can be generated
1897 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1898 the database schema once - see
1899 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1900 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1901 details on creating static schemas from a database).
1903 =head2 Move Common Startup into a Base Class
1905 Typically L<DBIx::Class> result classes start off with
1907 use base qw/DBIx::Class/;
1908 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1910 If this preamble is moved into a common base class:-
1914 use base qw/DBIx::Class/;
1915 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1918 and each result class then uses this as a base:-
1920 use base qw/MyDBICbase/;
1922 then the load_components is only performed once, which can result in a
1923 considerable startup speedup for schemas with many classes.
1925 =head2 Explicitly List Schema Result Classes
1927 The schema class will normally contain
1929 __PACKAGE__->load_classes();
1931 to load the result classes. This will use L<Module::Find|Module::Find>
1932 to find and load the appropriate modules. Explicitly defining the
1933 classes you wish to load will remove the overhead of
1934 L<Module::Find|Module::Find> and the related directory operations:
1936 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1938 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1939 syntax to load the appropriate classes there is not a direct alternative
1940 avoiding L<Module::Find|Module::Find>.
1944 =head2 Cached statements
1946 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
1947 This is normally a good idea, but if too many statements are cached, the database may use too much
1948 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
1949 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
1951 # print all currently cached prepared statements
1952 print for keys %{$schema->storage->dbh->{CachedKids}};
1953 # get a count of currently cached prepared statements
1954 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
1956 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
1959 my $kids = $schema->storage->dbh->{CachedKids};
1960 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
1962 But what you probably want is to expire unused statements and not those that are used frequently.
1963 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
1967 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
1968 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },