3 DBIx::Class::Manual::Cookbook - Miscellaneous recipes
9 When you expect a large number of results, you can ask L<DBIx::Class> for a
10 paged resultset, which will fetch only a defined number of records at a time:
12 my $rs = $schema->resultset('Artist')->search(
15 page => 1, # page to return (defaults to 1)
16 rows => 10, # number of results per page
20 return $rs->all(); # all records for page 1
22 return $rs->page(2); # records for page 2
24 You can get a L<Data::Page> object for the resultset (suitable for use
25 in e.g. a template) using the C<pager> method:
29 =head2 Complex WHERE clauses
31 Sometimes you need to formulate a query using specific operators:
33 my @albums = $schema->resultset('Album')->search({
34 artist => { 'like', '%Lamb%' },
35 title => { 'like', '%Fear of Fours%' },
38 This results in something like the following C<WHERE> clause:
40 WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
42 Other queries might require slightly more complex logic:
44 my @albums = $schema->resultset('Album')->search({
47 artist => { 'like', '%Smashing Pumpkins%' },
48 title => 'Siamese Dream',
50 artist => 'Starchildren',
54 This results in the following C<WHERE> clause:
56 WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
57 OR artist = 'Starchildren'
59 For more information on generating complex queries, see
60 L<SQL::Abstract/WHERE CLAUSES>.
62 =head2 Retrieve one and only one row from a resultset
64 Sometimes you need only the first "top" row of a resultset. While this
65 can be easily done with L<< $rs->first|DBIx::Class::ResultSet/first
66 >>, it is suboptimal, as a full blown cursor for the resultset will be
67 created and then immediately destroyed after fetching the first row
68 object. L<< $rs->single|DBIx::Class::ResultSet/single >> is designed
69 specifically for this case - it will grab the first returned result
70 without even instantiating a cursor.
72 Before replacing all your calls to C<first()> with C<single()> please observe the
79 While single() takes a search condition just like search() does, it does
80 _not_ accept search attributes. However one can always chain a single() to
83 my $top_cd = $cd_rs->search({}, { order_by => 'rating' })->single;
88 Since single() is the engine behind find(), it is designed to fetch a
89 single row per database query. Thus a warning will be issued when the
90 underlying SELECT returns more than one row. Sometimes however this usage
91 is valid: i.e. we have an arbitrary number of cd's but only one of them is
92 at the top of the charts at any given time. If you know what you are doing,
93 you can silence the warning by explicitly limiting the resultset size:
95 my $top_cd = $cd_rs->search ({}, { order_by => 'rating', rows => 1 })->single;
99 =head2 Arbitrary SQL through a custom ResultSource
101 Sometimes you have to run arbitrary SQL because your query is too complex
102 (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
103 be optimized for your database in a special way, but you still want to
104 get the results as a L<DBIx::Class::ResultSet>.
106 This is accomplished by defining a
107 L<ResultSource::View|DBIx::Class::ResultSource::View> for your query,
108 almost like you would define a regular ResultSource.
110 package My::Schema::Result::UserFriendsComplex;
113 use base qw/DBIx::Class/;
115 __PACKAGE__->load_components('Core');
116 __PACKAGE__->table_class('DBIx::Class::ResultSource::View');
118 # ->table, ->add_columns, etc.
120 # do not attempt to deploy() this view
121 __PACKAGE__->result_source_instance->is_virtual(1);
123 __PACKAGE__->result_source_instance->view_definition(q[
124 SELECT u.* FROM user u
125 INNER JOIN user_friends f ON u.id = f.user_id
126 WHERE f.friend_user_id = ?
128 SELECT u.* FROM user u
129 INNER JOIN user_friends f ON u.id = f.friend_user_id
133 Next, you can execute your complex query using bind parameters like this:
135 my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {},
137 bind => [ 12345, 12345 ]
141 ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
142 that you cannot modify the rows it contains, ie. cannot call L</update>,
143 L</delete>, ... on it).
145 Note that you cannot have bind parameters unless is_virtual is set to true.
151 If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >>
152 method for custom SQL execution, you are highly encouraged to update your code
153 to use a virtual view as above. If you do not want to change your code, and just
154 want to suppress the deprecation warning when you call
155 L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that
156 C<deploy> will exclude this "table":
158 sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) }
162 =head2 Using specific columns
164 When you only want specific columns from a table, you can use
165 C<columns> to specify which ones you need. This is useful to avoid
166 loading columns with large amounts of data that you aren't about to
169 my $rs = $schema->resultset('Artist')->search(
172 columns => [qw/ name /]
177 # SELECT artist.name FROM artist
179 This is a shortcut for C<select> and C<as>, see below. C<columns>
180 cannot be used together with C<select> and C<as>.
182 =head2 Using database functions or stored procedures
184 The combination of C<select> and C<as> can be used to return the result of a
185 database function or stored procedure as a column value. You use C<select> to
186 specify the source for your column value (e.g. a column name, function, or
187 stored procedure name). You then use C<as> to set the column name you will use
188 to access the returned value:
190 my $rs = $schema->resultset('Artist')->search(
193 select => [ 'name', { LENGTH => 'name' } ],
194 as => [qw/ name name_length /],
199 # SELECT name name, LENGTH( name )
202 Note that the C< as > attribute has absolutely nothing to with the sql
203 syntax C< SELECT foo AS bar > (see the documentation in
204 L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
205 column in your base class (i.e. it was added with C<add_columns>), you
206 just access it as normal. Our C<Artist> class has a C<name> column, so
207 we just use the C<name> accessor:
209 my $artist = $rs->first();
210 my $name = $artist->name();
212 If on the other hand the alias does not correspond to an existing column, you
213 have to fetch the value using the C<get_column> accessor:
215 my $name_length = $artist->get_column('name_length');
217 If you don't like using C<get_column>, you can always create an accessor for
218 any of your aliases using either of these:
220 # Define accessor manually:
221 sub name_length { shift->get_column('name_length'); }
223 # Or use DBIx::Class::AccessorGroup:
224 __PACKAGE__->mk_group_accessors('column' => 'name_length');
226 =head2 SELECT DISTINCT with multiple columns
228 my $rs = $schema->resultset('Artist')->search(
231 columns => [ qw/artist_id name rank/ ],
236 my $rs = $schema->resultset('Artist')->search(
239 columns => [ qw/artist_id name rank/ ],
240 group_by => [ qw/artist_id name rank/ ],
245 # SELECT me.artist_id, me.name, me.rank
247 # GROUP BY artist_id, name, rank
249 =head2 SELECT COUNT(DISTINCT colname)
251 my $rs = $schema->resultset('Artist')->search(
254 columns => [ qw/name/ ],
259 my $rs = $schema->resultset('Artist')->search(
262 columns => [ qw/name/ ],
263 group_by => [ qw/name/ ],
267 my $count = $rs->count;
270 # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
272 =head2 Grouping results
274 L<DBIx::Class> supports C<GROUP BY> as follows:
276 my $rs = $schema->resultset('Artist')->search(
280 select => [ 'name', { count => 'cds.id' } ],
281 as => [qw/ name cd_count /],
282 group_by => [qw/ name /]
287 # SELECT name, COUNT( cd.id ) FROM artist
288 # LEFT JOIN cd ON artist.id = cd.artist
291 Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
292 are in any way unsure about the use of the attributes above (C< join
293 >, C< select >, C< as > and C< group_by >).
295 =head2 Subqueries (EXPERIMENTAL)
297 You can write subqueries relatively easily in DBIC.
299 my $inside_rs = $schema->resultset('Artist')->search({
300 name => [ 'Billy Joel', 'Brittany Spears' ],
303 my $rs = $schema->resultset('CD')->search({
304 artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
307 The usual operators ( =, !=, IN, NOT IN, etc) are supported.
309 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
310 The following will B<not> work:
312 my $rs = $schema->resultset('CD')->search({
313 artist_id => $inside_rs->get_column('id')->as_query,
318 Subqueries are supported in the where clause (first hashref), and in the
319 from, select, and +select attributes.
321 =head3 Correlated subqueries
323 my $cdrs = $schema->resultset('CD');
324 my $rs = $cdrs->search({
326 '=' => $cdrs->search(
327 { artist_id => { '=' => \'me.artist_id' } },
329 )->get_column('year')->max_rs->as_query,
333 That creates the following SQL:
335 SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
338 SELECT MAX(inner.year)
340 WHERE artist_id = me.artist_id
345 Please note that subqueries are considered an experimental feature.
347 =head2 Predefined searches
349 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
350 and defining often used searches as methods:
352 package My::DBIC::ResultSet::CD;
355 use base 'DBIx::Class::ResultSet';
357 sub search_cds_ordered {
360 return $self->search(
362 { order_by => 'name DESC' },
368 To use your resultset, first tell DBIx::Class to create an instance of it
369 for you, in your My::DBIC::Schema::CD class:
371 # class definition as normal
372 __PACKAGE__->load_components(qw/ Core /);
373 __PACKAGE__->table('cd');
375 # tell DBIC to use the custom ResultSet class
376 __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
378 Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
380 Then call your new method in your code:
382 my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
384 =head2 Using SQL functions on the left hand side of a comparison
386 Using SQL functions on the left hand side of a comparison is generally
387 not a good idea since it requires a scan of the entire table. However,
388 it can be accomplished with C<DBIx::Class> when necessary.
390 If you do not have quoting on, simply include the function in your search
391 specification as you would any column:
393 $rs->search({ 'YEAR(date_of_birth)' => 1979 });
395 With quoting on, or for a more portable solution, use the C<where>
398 $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
402 (When the bind args ordering bug is fixed, this technique will be better
403 and can replace the one above.)
405 With quoting on, or for a more portable solution, use the C<where> and
409 where => \'YEAR(date_of_birth) = ?',
415 =head1 JOINS AND PREFETCHING
417 =head2 Using joins and prefetch
419 You can use the C<join> attribute to allow searching on, or sorting your
420 results by, one or more columns in a related table.
422 This requires that you have defined the L<DBIx::Class::Relationship>. For example :
424 My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id');
426 To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'):
428 my $rs = $schema->resultset('CD')->search(
430 'artists.name' => 'Bob Marley'
433 join => 'artists', # join the artist table
438 # SELECT cd.* FROM cd
439 # JOIN artist ON cd.artist = artist.id
440 # WHERE artist.name = 'Bob Marley'
442 In that example both the join, and the condition use the relationship name rather than the table name
443 (see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
445 If required, you can now sort on any column in the related tables by including
446 it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
448 my $rs = $schema->resultset('CD')->search(
450 'artists.name' => 'Bob Marley'
454 order_by => [qw/ artists.name /]
459 # SELECT cd.* FROM cd
460 # JOIN artist ON cd.artist = artist.id
461 # WHERE artist.name = 'Bob Marley'
462 # ORDER BY artist.name
464 Note that the C<join> attribute should only be used when you need to search or
465 sort using columns in a related table. Joining related tables when you only
466 need columns from the main table will make performance worse!
468 Now let's say you want to display a list of CDs, each with the name of the
469 artist. The following will work fine:
471 while (my $cd = $rs->next) {
472 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
475 There is a problem however. We have searched both the C<cd> and C<artist> tables
476 in our main query, but we have only returned data from the C<cd> table. To get
477 the artist name for any of the CD objects returned, L<DBIx::Class> will go back
480 SELECT artist.* FROM artist WHERE artist.id = ?
482 A statement like the one above will run for each and every CD returned by our
483 main query. Five CDs, five extra queries. A hundred CDs, one hundred extra
486 Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem.
487 This allows you to fetch results from related tables in advance:
489 my $rs = $schema->resultset('CD')->search(
491 'artists.name' => 'Bob Marley'
495 order_by => [qw/ artists.name /],
496 prefetch => 'artists' # return artist data too!
500 # Equivalent SQL (note SELECT from both "cd" and "artist"):
501 # SELECT cd.*, artist.* FROM cd
502 # JOIN artist ON cd.artist = artist.id
503 # WHERE artist.name = 'Bob Marley'
504 # ORDER BY artist.name
506 The code to print the CD list remains the same:
508 while (my $cd = $rs->next) {
509 print "CD: " . $cd->title . ", Artist: " . $cd->artist->name;
512 L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
513 so no additional SQL statements are executed. You now have a much more
516 Also note that C<prefetch> should only be used when you know you will
517 definitely use data from a related table. Pre-fetching related tables when you
518 only need columns from the main table will make performance worse!
520 =head2 Multiple joins
522 In the examples above, the C<join> attribute was a scalar. If you
523 pass an array reference instead, you can join to multiple tables. In
524 this example, we want to limit the search further, using
527 # Relationships defined elsewhere:
528 # CD->belongs_to('artist' => 'Artist');
529 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
530 my $rs = $schema->resultset('CD')->search(
532 'artist.name' => 'Bob Marley'
533 'liner_notes.notes' => { 'like', '%some text%' },
536 join => [qw/ artist liner_notes /],
537 order_by => [qw/ artist.name /],
542 # SELECT cd.*, artist.*, liner_notes.* FROM cd
543 # JOIN artist ON cd.artist = artist.id
544 # JOIN liner_notes ON cd.id = liner_notes.cd
545 # WHERE artist.name = 'Bob Marley'
546 # ORDER BY artist.name
548 =head2 Multi-step joins
550 Sometimes you want to join more than one relationship deep. In this example,
551 we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
552 contain a specific string:
554 # Relationships defined elsewhere:
555 # Artist->has_many('cds' => 'CD', 'artist');
556 # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
558 my $rs = $schema->resultset('Artist')->search(
560 'liner_notes.notes' => { 'like', '%some text%' },
564 'cds' => 'liner_notes'
570 # SELECT artist.* FROM artist
571 # LEFT JOIN cd ON artist.id = cd.artist
572 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
573 # WHERE liner_notes.notes LIKE '%some text%'
575 Joins can be nested to an arbitrary level. So if we decide later that we
576 want to reduce the number of Artists returned based on who wrote the liner
579 # Relationship defined elsewhere:
580 # LinerNotes->belongs_to('author' => 'Person');
582 my $rs = $schema->resultset('Artist')->search(
584 'liner_notes.notes' => { 'like', '%some text%' },
585 'author.name' => 'A. Writer'
590 'liner_notes' => 'author'
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 # LEFT JOIN author ON author.id = liner_notes.author
601 # WHERE liner_notes.notes LIKE '%some text%'
602 # AND author.name = 'A. Writer'
604 =head2 Multi-step and multiple joins
606 With various combinations of array and hash references, you can join
607 tables in any combination you desire. For example, to join Artist to
608 CD and Concert, and join CD to LinerNotes:
610 # Relationships defined elsewhere:
611 # Artist->has_many('concerts' => 'Concert', 'artist');
613 my $rs = $schema->resultset('Artist')->search(
626 # SELECT artist.* FROM artist
627 # LEFT JOIN cd ON artist.id = cd.artist
628 # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
629 # LEFT JOIN concert ON artist.id = concert.artist
631 =head2 Multi-step prefetch
633 C<prefetch> can be nested more than one relationship
634 deep using the same syntax as a multi-step join:
636 my $rs = $schema->resultset('Tag')->search(
646 # SELECT tag.*, cd.*, artist.* FROM tag
647 # JOIN cd ON tag.cd = cd.id
648 # JOIN artist ON cd.artist = artist.id
650 Now accessing our C<cd> and C<artist> relationships does not need additional
653 my $tag = $rs->first;
654 print $tag->cd->artist->name;
656 =head1 ROW-LEVEL OPERATIONS
658 =head2 Retrieving a row object's Schema
660 It is possible to get a Schema object from a row object like so:
662 my $schema = $cd->result_source->schema;
663 # use the schema as normal:
664 my $artist_rs = $schema->resultset('Artist');
666 This can be useful when you don't want to pass around a Schema object to every
669 =head2 Getting the value of the primary key for the last database insert
671 AKA getting last_insert_id
673 Thanks to the core component PK::Auto, this is straightforward:
675 my $foo = $rs->create(\%blah);
677 my $id = $foo->id; # foo->my_primary_key_field will also work.
679 If you are not using autoincrementing primary keys, this will probably
680 not work, but then you already know the value of the last primary key anyway.
682 =head2 Stringification
684 Employ the standard stringification technique by using the L<overload>
687 To make an object stringify itself as a single column, use something
688 like this (replace C<name> with the column/method of your choice):
690 use overload '""' => sub { shift->name}, fallback => 1;
692 For more complex stringification, you can use an anonymous subroutine:
694 use overload '""' => sub { $_[0]->name . ", " .
695 $_[0]->address }, fallback => 1;
697 =head3 Stringification Example
699 Suppose we have two tables: C<Product> and C<Category>. The table
702 Product(id, Description, category)
703 Category(id, Description)
705 C<category> is a foreign key into the Category table.
707 If you have a Product object C<$obj> and write something like
711 things will not work as expected.
713 To obtain, for example, the category description, you should add this
714 method to the class defining the Category table:
716 use overload "" => sub {
719 return $self->Description;
722 =head2 Want to know if find_or_create found or created a row?
724 Just use C<find_or_new> instead, then check C<in_storage>:
726 my $obj = $rs->find_or_new({ blah => 'blarg' });
727 unless ($obj->in_storage) {
729 # do whatever else you wanted if it was a new row
732 =head2 Static sub-classing DBIx::Class result classes
734 AKA adding additional relationships/methods/etc. to a model for a
735 specific usage of the (shared) model.
739 package My::App::Schema;
741 use base DBIx::Class::Schema;
743 # load subclassed classes from My::App::Schema::Result/ResultSet
744 __PACKAGE__->load_namespaces;
746 # load classes from shared model
748 'My::Shared::Model::Result' => [qw/
755 B<Result-Subclass definition>
757 package My::App::Schema::Result::Baz;
761 use base My::Shared::Model::Result::Baz;
763 # WARNING: Make sure you call table() again in your subclass,
764 # otherwise DBIx::Class::ResultSourceProxy::Table will not be called
765 # and the class name is not correctly registered as a source
766 __PACKAGE__->table('baz');
768 sub additional_method {
769 return "I'm an additional method only needed by this app";
774 =head2 Dynamic Sub-classing DBIx::Class proxy classes
776 AKA multi-class object inflation from one table
778 L<DBIx::Class> classes are proxy classes, therefore some different
779 techniques need to be employed for more than basic subclassing. In
780 this example we have a single user table that carries a boolean bit
781 for admin. We would like like to give the admin users
782 objects (L<DBIx::Class::Row>) the same methods as a regular user but
783 also special admin only methods. It doesn't make sense to create two
784 seperate proxy-class files for this. We would be copying all the user
785 methods into the Admin class. There is a cleaner way to accomplish
788 Overriding the C<inflate_result> method within the User proxy-class
789 gives us the effect we want. This method is called by
790 L<DBIx::Class::ResultSet> when inflating a result from storage. So we
791 grab the object being returned, inspect the values we are looking for,
792 bless it if it's an admin object, and then return it. See the example
799 use base qw/DBIx::Class::Schema/;
801 __PACKAGE__->load_namespaces;
806 B<Proxy-Class definitions>
808 package My::Schema::Result::User;
812 use base qw/DBIx::Class/;
814 ### Define what our admin class is, for ensure_class_loaded()
815 my $admin_class = __PACKAGE__ . '::Admin';
817 __PACKAGE__->load_components(qw/Core/);
819 __PACKAGE__->table('users');
821 __PACKAGE__->add_columns(qw/user_id email password
822 firstname lastname active
825 __PACKAGE__->set_primary_key('user_id');
829 my $ret = $self->next::method(@_);
830 if( $ret->admin ) {### If this is an admin, rebless for extra functions
831 $self->ensure_class_loaded( $admin_class );
832 bless $ret, $admin_class;
838 print "I am a regular user.\n";
845 package My::Schema::Result::User::Admin;
849 use base qw/My::Schema::Result::User/;
851 # This line is important
852 __PACKAGE__->table('users');
856 print "I am an admin.\n";
862 print "I am doing admin stuff\n";
874 my $user_data = { email => 'someguy@place.com',
878 my $admin_data = { email => 'someadmin@adminplace.com',
882 my $schema = My::Schema->connection('dbi:Pg:dbname=test');
884 $schema->resultset('User')->create( $user_data );
885 $schema->resultset('User')->create( $admin_data );
887 ### Now we search for them
888 my $user = $schema->resultset('User')->single( $user_data );
889 my $admin = $schema->resultset('User')->single( $admin_data );
891 print ref $user, "\n";
892 print ref $admin, "\n";
894 print $user->password , "\n"; # pass1
895 print $admin->password , "\n";# pass2; inherited from User
896 print $user->hello , "\n";# I am a regular user.
897 print $admin->hello, "\n";# I am an admin.
899 ### The statement below will NOT print
900 print "I can do admin stuff\n" if $user->can('do_admin_stuff');
901 ### The statement below will print
902 print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
904 =head2 Skip row object creation for faster results
906 DBIx::Class is not built for speed, it's built for convenience and
907 ease of use, but sometimes you just need to get the data, and skip the
910 To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
912 my $rs = $schema->resultset('CD');
914 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
916 my $hash_ref = $rs->find(1);
920 Beware, changing the Result class using
921 L<DBIx::Class::ResultSet/result_class> will replace any existing class
922 completely including any special components loaded using
923 load_components, eg L<DBIx::Class::InflateColumn::DateTime>.
925 =head2 Get raw data for blindingly fast results
927 If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
928 above is not fast enough for you, you can use a DBIx::Class to return values
929 exactly as they come out of the database with none of the convenience methods
932 This is used like so:
934 my $cursor = $rs->cursor
935 while (my @vals = $cursor->next) {
936 # use $val[0..n] here
939 You will need to map the array offsets to particular columns (you can
940 use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering).
942 =head1 RESULTSET OPERATIONS
944 =head2 Getting Schema from a ResultSet
946 To get the L<DBIx::Class::Schema> object from a ResultSet, do the following:
948 $rs->result_source->schema
950 =head2 Getting Columns Of Data
954 If you want to find the sum of a particular column there are several
955 ways, the obvious one is to use search:
957 my $rs = $schema->resultset('Items')->search(
960 select => [ { sum => 'Cost' } ],
961 as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
964 my $tc = $rs->first->get_column('total_cost');
966 Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
967 returned when you ask the C<ResultSet> for a column using
970 my $cost = $schema->resultset('Items')->get_column('Cost');
973 With this you can also do:
975 my $minvalue = $cost->min;
976 my $maxvalue = $cost->max;
978 Or just iterate through the values of this column only:
980 while ( my $c = $cost->next ) {
984 foreach my $c ($cost->all) {
988 C<ResultSetColumn> only has a limited number of built-in functions. If
989 you need one that it doesn't have, then you can use the C<func> method
992 my $avg = $cost->func('AVERAGE');
994 This will cause the following SQL statement to be run:
996 SELECT AVERAGE(Cost) FROM Items me
998 Which will of course only work if your database supports this function.
999 See L<DBIx::Class::ResultSetColumn> for more documentation.
1001 =head2 Creating a result set from a set of rows
1003 Sometimes you have a (set of) row objects that you want to put into a
1004 resultset without the need to hit the DB again. You can do that by using the
1005 L<set_cache|DBIx::Class::Resultset/set_cache> method:
1007 my @uploadable_groups;
1008 while (my $group = $groups->next) {
1009 if ($group->can_upload($self)) {
1010 push @uploadable_groups, $group;
1013 my $new_rs = $self->result_source->resultset;
1014 $new_rs->set_cache(\@uploadable_groups);
1018 =head1 USING RELATIONSHIPS
1020 =head2 Create a new row in a related table
1022 my $author = $book->create_related('author', { name => 'Fred'});
1024 =head2 Search in a related table
1026 Only searches for books named 'Titanic' by the author in $author.
1028 my $books_rs = $author->search_related('books', { name => 'Titanic' });
1030 =head2 Delete data in a related table
1032 Deletes only the book named Titanic by the author in $author.
1034 $author->delete_related('books', { name => 'Titanic' });
1036 =head2 Ordering a relationship result set
1038 If you always want a relation to be ordered, you can specify this when you
1039 create the relationship.
1041 To order C<< $book->pages >> by descending page_number, create the relation
1044 __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
1046 =head2 Filtering a relationship result set
1048 If you want to get a filtered result set, you can just add add to $attr as follows:
1050 __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
1052 =head2 Many-to-many relationships
1054 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
1057 use base 'DBIx::Class';
1058 __PACKAGE__->load_components('Core');
1059 __PACKAGE__->table('user');
1060 __PACKAGE__->add_columns(qw/id name/);
1061 __PACKAGE__->set_primary_key('id');
1062 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
1063 __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
1065 package My::UserAddress;
1066 use base 'DBIx::Class';
1067 __PACKAGE__->load_components('Core');
1068 __PACKAGE__->table('user_address');
1069 __PACKAGE__->add_columns(qw/user address/);
1070 __PACKAGE__->set_primary_key(qw/user address/);
1071 __PACKAGE__->belongs_to('user' => 'My::User');
1072 __PACKAGE__->belongs_to('address' => 'My::Address');
1074 package My::Address;
1075 use base 'DBIx::Class';
1076 __PACKAGE__->load_components('Core');
1077 __PACKAGE__->table('address');
1078 __PACKAGE__->add_columns(qw/id street town area_code country/);
1079 __PACKAGE__->set_primary_key('id');
1080 __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
1081 __PACKAGE__->many_to_many('users' => 'user_address', 'user');
1083 $rs = $user->addresses(); # get all addresses for a user
1084 $rs = $address->users(); # get all users for an address
1086 =head2 Relationships across DB schemas
1088 Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
1089 is easy as long as the schemas themselves are all accessible via the same DBI
1090 connection. In most cases, this means that they are on the same database host
1091 as each other and your connecting database user has the proper permissions to them.
1093 To accomplish this one only needs to specify the DB schema name in the table
1094 declaration, like so...
1096 package MyDatabase::Main::Artist;
1097 use base qw/DBIx::Class/;
1098 __PACKAGE__->load_components(qw/PK::Auto Core/);
1100 __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
1102 __PACKAGE__->add_columns(qw/ artist_id name /);
1103 __PACKAGE__->set_primary_key('artist_id');
1104 __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
1108 Whatever string you specify there will be used to build the "FROM" clause in SQL
1111 The big drawback to this is you now have DB schema names hardcoded in your
1112 class files. This becomes especially troublesome if you have multiple instances
1113 of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and
1114 the DB schemas are named based on the environment (e.g. database1_dev).
1116 However, one can dynamically "map" to the proper DB schema by overriding the
1117 L<connection|DBIx::Class::Schama/connection> method in your Schema class and
1118 building a renaming facility, like so:
1120 package MyDatabase::Schema;
1123 extends 'DBIx::Class::Schema';
1125 around connection => sub {
1126 my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
1128 my $postfix = delete $attr->{schema_name_postfix};
1133 $self->append_db_name($postfix);
1137 sub append_db_name {
1138 my ( $self, $postfix ) = @_;
1142 { $_->name =~ /^\w+\./mx }
1144 { $self->source($_) }
1147 foreach my $source (@sources_with_db) {
1148 my $name = $source->name;
1149 $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
1151 $source->name($name);
1157 By overridding the L<connection|DBIx::Class::Schama/connection>
1158 method and extracting a custom option from the provided \%attr hashref one can
1159 then simply iterate over all the Schema's ResultSources, renaming them as
1162 To use this facility, simply add or modify the \%attr hashref that is passed to
1163 L<connection|DBIx::Class::Schama/connect>, as follows:
1166 = MyDatabase::Schema->connect(
1171 schema_name_postfix => '_dev'
1172 # ... Other options as desired ...
1175 Obviously, one could accomplish even more advanced mapping via a hash map or a
1180 As of version 0.04001, there is improved transaction support in
1181 L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
1182 example of the recommended way to use it:
1184 my $genus = $schema->resultset('Genus')->find(12);
1186 my $coderef2 = sub {
1191 my $coderef1 = sub {
1192 $genus->add_to_species({ name => 'troglodyte' });
1195 $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
1196 return $genus->species;
1201 $rs = $schema->txn_do($coderef1);
1204 if ($@) { # Transaction failed
1205 die "the sky is falling!" #
1206 if ($@ =~ /Rollback failed/); # Rollback failed
1208 deal_with_failed_transaction();
1211 Nested transactions will work as expected. That is, only the outermost
1212 transaction will actually issue a commit to the $dbh, and a rollback
1213 at any level of any transaction will cause the entire nested
1214 transaction to fail. Support for savepoints and for true nested
1215 transactions (for databases that support them) will hopefully be added
1220 =head2 Creating Schemas From An Existing Database
1222 L<DBIx::Class::Schema::Loader> will connect to a database and create a
1223 L<DBIx::Class::Schema> and associated sources by examining the database.
1225 The recommend way of achieving this is to use the
1226 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
1228 perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
1229 -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
1231 This will create a tree of files rooted at C<./lib/My/Schema/> containing
1232 source definitions for all the tables found in the C<foo> database.
1234 =head2 Creating DDL SQL
1236 The following functionality requires you to have L<SQL::Translator>
1237 (also known as "SQL Fairy") installed.
1239 To create a set of database-specific .sql files for the above schema:
1241 my $schema = My::Schema->connect($dsn);
1242 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1247 By default this will create schema files in the current directory, for
1248 MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
1250 To create a new database using the schema:
1252 my $schema = My::Schema->connect($dsn);
1253 $schema->deploy({ add_drop_tables => 1});
1255 To import created .sql files using the mysql client:
1257 mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
1259 To create C<ALTER TABLE> conversion scripts to update a database to a
1260 newer version of your schema at a later point, first set a new
1261 C<$VERSION> in your Schema file, then:
1263 my $schema = My::Schema->connect($dsn);
1264 $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
1270 This will produce new database-specific .sql files for the new version
1271 of the schema, plus scripts to convert from version 0.1 to 0.2. This
1272 requires that the files for 0.1 as created above are available in the
1273 given directory to diff against.
1275 =head2 Select from dual
1277 Dummy tables are needed by some databases to allow calling functions
1278 or expressions that aren't based on table content, for examples of how
1279 this applies to various database types, see:
1280 L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
1282 Note: If you're using Oracles dual table don't B<ever> do anything
1283 other than a select, if you CRUD on your dual table you *will* break
1286 Make a table class as you would for any other table
1288 package MyAppDB::Dual;
1291 use base 'DBIx::Class';
1292 __PACKAGE__->load_components("Core");
1293 __PACKAGE__->table("Dual");
1294 __PACKAGE__->add_columns(
1296 { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
1299 Once you've loaded your table class select from it using C<select>
1300 and C<as> instead of C<columns>
1302 my $rs = $schema->resultset('Dual')->search(undef,
1303 { select => [ 'sydate' ],
1308 All you have to do now is be careful how you access your resultset, the below
1309 will not work because there is no column called 'now' in the Dual table class
1311 while (my $dual = $rs->next) {
1312 print $dual->now."\n";
1314 # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
1316 You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
1317 your Dual class for whatever you wanted to select from dual, but that's just
1318 silly, instead use C<get_column>
1320 while (my $dual = $rs->next) {
1321 print $dual->get_column('now')."\n";
1326 my $cursor = $rs->cursor;
1327 while (my @vals = $cursor->next) {
1328 print $vals[0]."\n";
1331 In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or
1332 L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your
1333 current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or
1334 "sequence.nextval" anymore from dual. To avoid this problem, just tell
1335 L<SQL::Translator> to not create table dual:
1338 add_drop_table => 1,
1339 parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
1341 $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
1343 Or use L<DBIx::Class::ResultClass::HashRefInflator>
1345 $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
1346 while ( my $dual = $rs->next ) {
1347 print $dual->{now}."\n";
1350 Here are some example C<select> conditions to illustrate the different syntax
1351 you could use for doing stuff like
1352 C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
1354 # get a sequence value
1355 select => [ 'A_SEQ.nextval' ],
1357 # get create table sql
1358 select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
1360 # get a random num between 0 and 100
1361 select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
1364 select => [ { 'extract' => [ \'year from sysdate' ] } ],
1367 select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
1369 # which day of the week were you born on?
1370 select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
1372 # select 16 rows from dual
1373 select => [ "'hello'" ],
1375 group_by => [ 'cube( 1, 2, 3, 4 )' ],
1379 =head2 Adding Indexes And Functions To Your SQL
1381 Often you will want indexes on columns on your table to speed up searching. To
1382 do this, create a method called C<sqlt_deploy_hook> in the relevant source
1383 class (refer to the advanced
1384 L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
1385 to share a hook between multiple sources):
1387 package My::Schema::Result::Artist;
1389 __PACKAGE__->table('artist');
1390 __PACKAGE__->add_columns(id => { ... }, name => { ... })
1392 sub sqlt_deploy_hook {
1393 my ($self, $sqlt_table) = @_;
1395 $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
1400 Sometimes you might want to change the index depending on the type of the
1401 database for which SQL is being generated:
1403 my ($db_type = $sqlt_table->schema->translator->producer_type)
1404 =~ s/^SQL::Translator::Producer:://;
1406 You can also add hooks to the schema level to stop certain tables being
1413 sub sqlt_deploy_hook {
1414 my ($self, $sqlt_schema) = @_;
1416 $sqlt_schema->drop_table('table_name');
1419 You could also add views, procedures or triggers to the output using
1420 L<SQL::Translator::Schema/add_view>,
1421 L<SQL::Translator::Schema/add_procedure> or
1422 L<SQL::Translator::Schema/add_trigger>.
1425 =head2 Schema versioning
1427 The following example shows simplistically how you might use DBIx::Class to
1428 deploy versioned schemas to your customers. The basic process is as follows:
1434 Create a DBIx::Class schema
1446 Modify schema to change functionality
1450 Deploy update to customers
1454 B<Create a DBIx::Class schema>
1456 This can either be done manually, or generated from an existing database as
1457 described under L</Creating Schemas From An Existing Database>
1461 Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
1463 B<Deploy to customers>
1465 There are several ways you could deploy your schema. These are probably
1466 beyond the scope of this recipe, but might include:
1472 Require customer to apply manually using their RDBMS.
1476 Package along with your app, making database dump/schema update/tests
1477 all part of your install.
1481 B<Modify the schema to change functionality>
1483 As your application evolves, it may be necessary to modify your schema
1484 to change functionality. Once the changes are made to your schema in
1485 DBIx::Class, export the modified schema and the conversion scripts as
1486 in L</Creating DDL SQL>.
1488 B<Deploy update to customers>
1490 Add the L<DBIx::Class::Schema::Versioned> schema component to your
1491 Schema class. This will add a new table to your database called
1492 C<dbix_class_schema_vesion> which will keep track of which version is installed
1493 and warn if the user trys to run a newer schema version than the
1494 database thinks it has.
1496 Alternatively, you can send the conversion sql scripts to your
1499 =head2 Setting quoting for the generated SQL.
1501 If the database contains column names with spaces and/or reserved words, they
1502 need to be quoted in the SQL queries. This is done using:
1504 __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
1505 __PACKAGE__->storage->sql_maker->name_sep('.');
1507 The first sets the quote characters. Either a pair of matching
1508 brackets, or a C<"> or C<'>:
1510 __PACKAGE__->storage->sql_maker->quote_char('"');
1512 Check the documentation of your database for the correct quote
1513 characters to use. C<name_sep> needs to be set to allow the SQL
1514 generator to put the quotes the correct place.
1516 In most cases you should set these as part of the arguments passed to
1517 L<DBIx::Class::Schema/connect>:
1519 my $schema = My::Schema->connect(
1529 =head2 Setting limit dialect for SQL::Abstract::Limit
1531 In some cases, SQL::Abstract::Limit cannot determine the dialect of
1532 the remote SQL server by looking at the database handle. This is a
1533 common problem when using the DBD::JDBC, since the DBD-driver only
1534 know that in has a Java-driver available, not which JDBC driver the
1535 Java component has loaded. This specifically sets the limit_dialect
1536 to Microsoft SQL-server (See more names in SQL::Abstract::Limit
1539 __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
1541 The JDBC bridge is one way of getting access to a MSSQL server from a platform
1542 that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
1544 The limit dialect can also be set at connect time by specifying a
1545 C<limit_dialect> key in the final hash as shown above.
1547 =head2 Working with PostgreSQL array types
1549 You can also assign values to PostgreSQL array columns by passing array
1550 references in the C<\%columns> (C<\%vals>) hashref of the
1551 L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of
1554 $resultset->create({
1555 numbers => [1, 2, 3]
1560 numbers => [1, 2, 3]
1567 In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
1568 methods) you cannot directly use array references (since this is interpreted as
1569 a list of values to be C<OR>ed), but you can use the following syntax to force
1570 passing them as bind values:
1574 numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
1578 See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
1579 placeholders and bind values (subqueries)> for more explanation. Note that
1580 L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
1581 the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
1582 arrayrefs together with the column name, like this: C<< [column_name => value]
1585 =head1 BOOTSTRAPPING/MIGRATING
1587 =head2 Easy migration from class-based to schema-based setup
1589 You want to start using the schema-based approach to L<DBIx::Class>
1590 (see L<SchemaIntro.pod>), but have an established class-based setup with lots
1591 of existing classes that you don't want to move by hand. Try this nifty script
1595 use SQL::Translator;
1597 my $schema = MyDB->schema_instance;
1599 my $translator = SQL::Translator->new(
1600 debug => $debug || 0,
1601 trace => $trace || 0,
1602 no_comments => $no_comments || 0,
1603 show_warnings => $show_warnings || 0,
1604 add_drop_table => $add_drop_table || 0,
1605 validate => $validate || 0,
1607 'DBIx::Schema' => $schema,
1610 'prefix' => 'My::Schema',
1614 $translator->parser('SQL::Translator::Parser::DBIx::Class');
1615 $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
1617 my $output = $translator->translate(@args) or die
1618 "Error: " . $translator->error;
1622 You could use L<Module::Find> to search for all subclasses in the MyDB::*
1623 namespace, which is currently left as an exercise for the reader.
1625 =head1 OVERLOADING METHODS
1627 L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
1628 method calls, useful for things like default values and triggers. You have to
1629 use calls to C<next::method> to overload methods. More information on using
1630 L<Class::C3> with L<DBIx::Class> can be found in
1631 L<DBIx::Class::Manual::Component>.
1633 =head2 Setting default values for a row
1635 It's as simple as overriding the C<new> method. Note the use of
1639 my ( $class, $attrs ) = @_;
1641 $attrs->{foo} = 'bar' unless defined $attrs->{foo};
1643 my $new = $class->next::method($attrs);
1648 For more information about C<next::method>, look in the L<Class::C3>
1649 documentation. See also L<DBIx::Class::Manual::Component> for more
1650 ways to write your own base classes to do this.
1652 People looking for ways to do "triggers" with DBIx::Class are probably
1653 just looking for this.
1655 =head2 Changing one field whenever another changes
1657 For example, say that you have three columns, C<id>, C<number>, and
1658 C<squared>. You would like to make changes to C<number> and have
1659 C<squared> be automagically set to the value of C<number> squared.
1660 You can accomplish this by overriding C<store_column>:
1663 my ( $self, $name, $value ) = @_;
1664 if ($name eq 'number') {
1665 $self->squared($value * $value);
1667 $self->next::method($name, $value);
1670 Note that the hard work is done by the call to C<next::method>, which
1671 redispatches your call to store_column in the superclass(es).
1673 =head2 Automatically creating related objects
1675 You might have a class C<Artist> which has many C<CD>s. Further, you
1676 want to create a C<CD> object every time you insert an C<Artist> object.
1677 You can accomplish this by overriding C<insert> on your objects:
1680 my ( $self, @args ) = @_;
1681 $self->next::method(@args);
1682 $self->cds->new({})->fill_from_artist($self)->insert;
1686 where C<fill_from_artist> is a method you specify in C<CD> which sets
1687 values in C<CD> based on the data in the C<Artist> object you pass in.
1689 =head2 Wrapping/overloading a column accessor
1693 Say you have a table "Camera" and want to associate a description
1694 with each camera. For most cameras, you'll be able to generate the description from
1695 the other columns. However, in a few special cases you may want to associate a
1696 custom description with a camera.
1700 In your database schema, define a description field in the "Camera" table that
1701 can contain text and null values.
1703 In DBIC, we'll overload the column accessor to provide a sane default if no
1704 custom description is defined. The accessor will either return or generate the
1705 description, depending on whether the field is null or not.
1707 First, in your "Camera" schema class, define the description field as follows:
1709 __PACKAGE__->add_columns(description => { accessor => '_description' });
1711 Next, we'll define the accessor-wrapper subroutine:
1716 # If there is an update to the column, we'll let the original accessor
1718 return $self->_description(@_) if @_;
1720 # Fetch the column value.
1721 my $description = $self->_description;
1723 # If there's something in the description field, then just return that.
1724 return $description if defined $description && length $descripton;
1726 # Otherwise, generate a description.
1727 return $self->generate_description;
1730 =head1 DEBUGGING AND PROFILING
1732 =head2 DBIx::Class objects with Data::Dumper
1734 L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
1735 be hard to find the pertinent data in all the data it can generate.
1736 Specifically, if one naively tries to use it like so,
1740 my $cd = $schema->resultset('CD')->find(1);
1743 several pages worth of data from the CD object's schema and result source will
1744 be dumped to the screen. Since usually one is only interested in a few column
1745 values of the object, this is not very helpful.
1747 Luckily, it is possible to modify the data before L<Data::Dumper> outputs
1748 it. Simply define a hook that L<Data::Dumper> will call on the object before
1749 dumping it. For example,
1756 result_source => undef,
1764 local $Data::Dumper::Freezer = '_dumper_hook';
1766 my $cd = $schema->resultset('CD')->find(1);
1768 # dumps $cd without its ResultSource
1770 If the structure of your schema is such that there is a common base class for
1771 all your table classes, simply put a method similar to C<_dumper_hook> in the
1772 base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
1773 will automagically clean up your data before printing it. See
1774 L<Data::Dumper/EXAMPLES> for more information.
1778 When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
1779 executed as well as notifications of query completion and transaction
1780 begin/commit. If you'd like to profile the SQL you can subclass the
1781 L<DBIx::Class::Storage::Statistics> class and write your own profiling
1784 package My::Profiler;
1787 use base 'DBIx::Class::Storage::Statistics';
1789 use Time::HiRes qw(time);
1798 $self->print("Executing $sql: ".join(', ', @params)."\n");
1807 my $elapsed = sprintf("%0.4f", time() - $start);
1808 $self->print("Execution took $elapsed seconds.\n");
1814 You can then install that class as the debugging object:
1816 __PACKAGE__->storage->debugobj(new My::Profiler());
1817 __PACKAGE__->storage->debug(1);
1819 A more complicated example might involve storing each execution of SQL in an
1827 my $elapsed = time() - $start;
1828 push(@{ $calls{$sql} }, {
1834 You could then create average, high and low execution times for an SQL
1835 statement and dig down to see if certain parameters cause aberrant behavior.
1836 You might want to check out L<DBIx::Class::QueryLog> as well.
1838 =head1 STARTUP SPEED
1840 L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
1841 as the ORM loads all the relevant classes. This section examines
1842 techniques for reducing the startup delay.
1844 These tips are are listed in order of decreasing effectiveness - so the
1845 first tip, if applicable, should have the greatest effect on your
1848 =head2 Statically Define Your Schema
1851 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
1852 classes dynamically based on the database schema then there will be a
1853 significant startup delay.
1855 For production use a statically defined schema (which can be generated
1856 using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
1857 the database schema once - see
1858 L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
1859 L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
1860 details on creating static schemas from a database).
1862 =head2 Move Common Startup into a Base Class
1864 Typically L<DBIx::Class> result classes start off with
1866 use base qw/DBIx::Class/;
1867 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1869 If this preamble is moved into a common base class:-
1873 use base qw/DBIx::Class/;
1874 __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1877 and each result class then uses this as a base:-
1879 use base qw/MyDBICbase/;
1881 then the load_components is only performed once, which can result in a
1882 considerable startup speedup for schemas with many classes.
1884 =head2 Explicitly List Schema Result Classes
1886 The schema class will normally contain
1888 __PACKAGE__->load_classes();
1890 to load the result classes. This will use L<Module::Find|Module::Find>
1891 to find and load the appropriate modules. Explicitly defining the
1892 classes you wish to load will remove the overhead of
1893 L<Module::Find|Module::Find> and the related directory operations:
1895 __PACKAGE__->load_classes(qw/ CD Artist Track /);
1897 If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
1898 syntax to load the appropriate classes there is not a direct alternative
1899 avoiding L<Module::Find|Module::Find>.
1903 =head2 Cached statements
1905 L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>.
1906 This is normally a good idea, but if too many statements are cached, the database may use too much
1907 memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want
1908 to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash:
1910 # print all currently cached prepared statements
1911 print for keys %{$schema->storage->dbh->{CachedKids}};
1912 # get a count of currently cached prepared statements
1913 my $count = scalar keys %{$schema->storage->dbh->{CachedKids}};
1915 If it's appropriate, you can simply clear these statements, automatically deallocating them in the
1918 my $kids = $schema->storage->dbh->{CachedKids};
1919 delete @{$kids}{keys %$kids} if scalar keys %$kids > 100;
1921 But what you probably want is to expire unused statements and not those that are used frequently.
1922 You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>:
1926 my $schema = DB::Main->connect($dbi_dsn, $user, $pass, {
1927 on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 },