-=head1 NAME
+=head1 NAME
DBIx::Class::Manual::Cookbook - Miscellaneous recipes
Sometimes you need only the first "top" row of a resultset. While this can be
easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal,
as a full blown cursor for the resultset will be created and then immediately
-destroyed after fetching the first row object.
+destroyed after fetching the first row object.
L<< $rs->single|DBIx::Class::ResultSet/single >> is
designed specifically for this case - it will grab the first returned result
-without even instantiating a cursor.
+without even instantiating a cursor.
-Before replacing all your calls to C<first()> with C<single()> please observe the
+Before replacing all your calls to C<first()> with C<single()> please observe the
following CAVEATS:
=over
Sometimes you have to run arbitrary SQL because your query is too complex
(e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to
-be optimized for your database in a special way, but you still want to
-get the results as a L<DBIx::Class::ResultSet>.
-The recommended way to accomplish this is by defining a separate ResultSource
-for your query. You can then inject complete SQL statements using a scalar
+be optimized for your database in a special way, but you still want to
+get the results as a L<DBIx::Class::ResultSet>.
+The recommended way to accomplish this is by defining a separate ResultSource
+for your query. You can then inject complete SQL statements using a scalar
reference (this is a feature of L<SQL::Abstract>).
Say you want to run a complex custom query on your user data, here's what
you have to add to your User class:
package My::Schema::Result::User;
-
+
use base qw/DBIx::Class/;
-
+
# ->load_components, ->table, ->add_columns, etc.
# Make a new ResultSource based on the User class
my $source = __PACKAGE__->result_source_instance();
my $new_source = $source->new( $source );
$new_source->source_name( 'UserFriendsComplex' );
-
+
# Hand in your query as a scalar reference
# It will be added as a sub-select after FROM,
# so pay attention to the surrounding brackets!
$new_source->name( \<<SQL );
- ( SELECT u.* FROM user u
- INNER JOIN user_friends f ON u.id = f.user_id
+ ( SELECT u.* FROM user u
+ INNER JOIN user_friends f ON u.id = f.user_id
WHERE f.friend_user_id = ?
- UNION
- SELECT u.* FROM user u
- INNER JOIN user_friends f ON u.id = f.friend_user_id
+ UNION
+ SELECT u.* FROM user u
+ INNER JOIN user_friends f ON u.id = f.friend_user_id
WHERE f.user_id = ? )
- SQL
+ SQL
# Finally, register your new ResultSource with your Schema
My::Schema->register_extra_source( 'UserFriendsComplex' => $new_source );
Next, you can execute your complex query using bind parameters like this:
- my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {},
+ my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {},
{
bind => [ 12345, 12345 ]
}
) ];
-
+
... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course,
that you cannot modify the rows it contains, ie. cannot call L</update>,
L</delete>, ... on it).
# Define accessor manually:
sub name_length { shift->get_column('name_length'); }
-
+
# Or use DBIx::Class::AccessorGroup:
__PACKAGE__->mk_group_accessors('column' => 'name_length');
{
columns => [ qw/artist_id name rank/ ],
distinct => 1
- }
+ }
);
my $rs = $schema->resultset('Artist')->search(
my $count = $rs->count;
# Equivalent SQL:
- # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
+ # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq:
=head2 Grouping results
=head2 Predefined searches
You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
-and define often used searches as methods:
+and defining often used searches as methods:
package My::DBIC::ResultSet::CD;
use strict;
my $rs = $schema->resultset('CD')->search(
{
- 'artists.name' => 'Bob Marley'
+ 'artists.name' => 'Bob Marley'
},
{
join => 'artists', # join the artist table
# WHERE artist.name = 'Bob Marley'
In that example both the join, and the condition use the relationship name rather than the table name
-(see DBIx::Class::Manual::Joining for more details on aliasing ).
+(see L<DBIx::Class::Manual::Joining> for more details on aliasing ).
If required, you can now sort on any column in the related tables by including
it in your C<order_by> attribute, (again using the aliased relation name rather than table name) :
my $schema = $cd->result_source->schema;
# use the schema as normal:
- my $artist_rs = $schema->resultset('Artist');
+ my $artist_rs = $schema->resultset('Artist');
This can be useful when you don't want to pass around a Schema object to every
method.
=head2 Stringification
-Employ the standard stringification technique by using the C<overload>
+Employ the standard stringification technique by using the L<overload>
module.
To make an object stringify itself as a single column, use something
# do whatever else you wanted if it was a new row
}
-=head2 Static sub-classing DBIx::Class result classes
+=head2 Static sub-classing DBIx::Class result classes
AKA adding additional relationships/methods/etc. to a model for a
specific usage of the (shared) model.
-B<Schema definition>
-
- package My::App::Schema;
-
- use base DBIx::Class::Schema;
+B<Schema definition>
+
+ package My::App::Schema;
+
+ use base DBIx::Class::Schema;
# load subclassed classes from My::App::Schema::Result/ResultSet
__PACKAGE__->load_namespaces;
/]});
1;
-
-B<Result-Subclass definition>
-
+
+B<Result-Subclass definition>
+
package My::App::Schema::Result::Baz;
-
- use strict;
- use warnings;
- use base My::Shared::Model::Result::Baz;
-
+
+ use strict;
+ use warnings;
+ use base My::Shared::Model::Result::Baz;
+
# WARNING: Make sure you call table() again in your subclass,
# otherwise DBIx::Class::ResultSourceProxy::Table will not be called
# and the class name is not correctly registered as a source
- __PACKAGE__->table('baz');
-
- sub additional_method {
- return "I'm an additional method only needed by this app";
+ __PACKAGE__->table('baz');
+
+ sub additional_method {
+ return "I'm an additional method only needed by this app";
}
1;
-
-=head2 Dynamic Sub-classing DBIx::Class proxy classes
+
+=head2 Dynamic Sub-classing DBIx::Class proxy classes
AKA multi-class object inflation from one table
-
+
L<DBIx::Class> classes are proxy classes, therefore some different
techniques need to be employed for more than basic subclassing. In
this example we have a single user table that carries a boolean bit
for admin. We would like like to give the admin users
-objects(L<DBIx::Class::Row>) the same methods as a regular user but
+objects (L<DBIx::Class::Row>) the same methods as a regular user but
also special admin only methods. It doesn't make sense to create two
seperate proxy-class files for this. We would be copying all the user
methods into the Admin class. There is a cleaner way to accomplish
grab the object being returned, inspect the values we are looking for,
bless it if it's an admin object, and then return it. See the example
below:
-
-B<Schema Definition>
-
- package My::Schema;
-
- use base qw/DBIx::Class::Schema/;
-
+
+B<Schema Definition>
+
+ package My::Schema;
+
+ use base qw/DBIx::Class::Schema/;
+
__PACKAGE__->load_namespaces;
1;
-
-
-B<Proxy-Class definitions>
-
- package My::Schema::Result::User;
-
- use strict;
- use warnings;
- use base qw/DBIx::Class/;
-
- ### Defined what our admin class is for ensure_class_loaded
- my $admin_class = __PACKAGE__ . '::Admin';
-
- __PACKAGE__->load_components(qw/Core/);
-
- __PACKAGE__->table('users');
-
- __PACKAGE__->add_columns(qw/user_id email password
- firstname lastname active
- admin/);
-
- __PACKAGE__->set_primary_key('user_id');
-
- sub inflate_result {
- my $self = shift;
- my $ret = $self->next::method(@_);
- if( $ret->admin ) {### If this is an admin rebless for extra functions
- $self->ensure_class_loaded( $admin_class );
- bless $ret, $admin_class;
- }
- return $ret;
- }
-
- sub hello {
- print "I am a regular user.\n";
- return ;
- }
-
+
+
+B<Proxy-Class definitions>
+
+ package My::Schema::Result::User;
+
+ use strict;
+ use warnings;
+ use base qw/DBIx::Class/;
+
+ ### Define what our admin class is, for ensure_class_loaded()
+ my $admin_class = __PACKAGE__ . '::Admin';
+
+ __PACKAGE__->load_components(qw/Core/);
+
+ __PACKAGE__->table('users');
+
+ __PACKAGE__->add_columns(qw/user_id email password
+ firstname lastname active
+ admin/);
+
+ __PACKAGE__->set_primary_key('user_id');
+
+ sub inflate_result {
+ my $self = shift;
+ my $ret = $self->next::method(@_);
+ if( $ret->admin ) {### If this is an admin, rebless for extra functions
+ $self->ensure_class_loaded( $admin_class );
+ bless $ret, $admin_class;
+ }
+ return $ret;
+ }
+
+ sub hello {
+ print "I am a regular user.\n";
+ return ;
+ }
+
1;
-
- package My::Schema::Result::User::Admin;
-
- use strict;
- use warnings;
- use base qw/My::Schema::Result::User/;
+
+ package My::Schema::Result::User::Admin;
+
+ use strict;
+ use warnings;
+ use base qw/My::Schema::Result::User/;
# This line is important
__PACKAGE__->table('users');
-
- sub hello
- {
- print "I am an admin.\n";
- return;
- }
-
- sub do_admin_stuff
- {
- print "I am doing admin stuff\n";
- return ;
+
+ sub hello
+ {
+ print "I am an admin.\n";
+ return;
+ }
+
+ sub do_admin_stuff
+ {
+ print "I am doing admin stuff\n";
+ return ;
}
1;
-
-B<Test File> test.pl
-
- use warnings;
- use strict;
- use My::Schema;
-
- my $user_data = { email => 'someguy@place.com',
- password => 'pass1',
- admin => 0 };
-
- my $admin_data = { email => 'someadmin@adminplace.com',
- password => 'pass2',
- admin => 1 };
-
- my $schema = My::Schema->connection('dbi:Pg:dbname=test');
-
- $schema->resultset('User')->create( $user_data );
- $schema->resultset('User')->create( $admin_data );
-
- ### Now we search for them
- my $user = $schema->resultset('User')->single( $user_data );
- my $admin = $schema->resultset('User')->single( $admin_data );
-
- print ref $user, "\n";
- print ref $admin, "\n";
-
- print $user->password , "\n"; # pass1
- print $admin->password , "\n";# pass2; inherited from User
- print $user->hello , "\n";# I am a regular user.
- print $admin->hello, "\n";# I am an admin.
-
- ### The statement below will NOT print
- print "I can do admin stuff\n" if $user->can('do_admin_stuff');
- ### The statement below will print
- print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
+
+B<Test File> test.pl
+
+ use warnings;
+ use strict;
+ use My::Schema;
+
+ my $user_data = { email => 'someguy@place.com',
+ password => 'pass1',
+ admin => 0 };
+
+ my $admin_data = { email => 'someadmin@adminplace.com',
+ password => 'pass2',
+ admin => 1 };
+
+ my $schema = My::Schema->connection('dbi:Pg:dbname=test');
+
+ $schema->resultset('User')->create( $user_data );
+ $schema->resultset('User')->create( $admin_data );
+
+ ### Now we search for them
+ my $user = $schema->resultset('User')->single( $user_data );
+ my $admin = $schema->resultset('User')->single( $admin_data );
+
+ print ref $user, "\n";
+ print ref $admin, "\n";
+
+ print $user->password , "\n"; # pass1
+ print $admin->password , "\n";# pass2; inherited from User
+ print $user->hello , "\n";# I am a regular user.
+ print $admin->hello, "\n";# I am an admin.
+
+ ### The statement below will NOT print
+ print "I can do admin stuff\n" if $user->can('do_admin_stuff');
+ ### The statement below will print
+ print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
=head2 Skip row object creation for faster results
DBIx::Class is not built for speed, it's built for convenience and
ease of use, but sometimes you just need to get the data, and skip the
fancy objects.
-
+
To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
-
+
my $rs = $schema->resultset('CD');
-
+
$rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
-
+
my $hash_ref = $rs->find(1);
Wasn't that easy?
my $rs = $schema->resultset('Items')->search(
{},
- {
+ {
select => [ { sum => 'Cost' } ],
as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
}
print $c;
}
-C<ResultSetColumn> only has a limited number of built-in functions, if
+C<ResultSetColumn> only has a limited number of built-in functions. If
you need one that it doesn't have, then you can use the C<func> method
instead:
=head2 Creating a result set from a set of rows
-Sometimes you have a (set of) row objects that you want to put into a
+Sometimes you have a (set of) row objects that you want to put into a
resultset without the need to hit the DB again. You can do that by using the
L<set_cache|DBIx::Class::Resultset/set_cache> method:
=head2 Ordering a relationship result set
-If you always want a relation to be ordered, you can specify this when you
+If you always want a relation to be ordered, you can specify this when you
create the relationship.
To order C<< $book->pages >> by descending page_number, create the relation
package MyDatabase::Main::Artist;
use base qw/DBIx::Class/;
__PACKAGE__->load_components(qw/PK::Auto Core/);
-
+
__PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
-
+
__PACKAGE__->add_columns(qw/ artist_id name /);
__PACKAGE__->set_primary_key('artist_id');
__PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd');
package MyDatabase::Schema;
use Moose;
-
+
extends 'DBIx::Class::Schema';
-
+
around connection => sub {
my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ );
-
+
my $postfix = delete $attr->{schema_name_postfix};
-
+
$inner->(@_);
-
+
if ( $postfix ) {
$self->append_db_name($postfix);
}
sub append_db_name {
my ( $self, $postfix ) = @_;
-
- my @sources_with_db
- = grep
- { $_->name =~ /^\w+\./mx }
- map
- { $self->source($_) }
+
+ my @sources_with_db
+ = grep
+ { $_->name =~ /^\w+\./mx }
+ map
+ { $self->source($_) }
$self->sources;
-
+
foreach my $source (@sources_with_db) {
my $name = $source->name;
$name =~ s{^(\w+)\.}{${1}${postfix}\.}mx;
-
+
$source->name($name);
}
}
then simply iterate over all the Schema's ResultSources, renaming them as
needed.
-To use this facility, simply add or modify the \%attr hashref that is passed to
+To use this facility, simply add or modify the \%attr hashref that is passed to
L<connection|DBIx::Class::Schama/connect>, as follows:
- my $schema
+ my $schema
= MyDatabase::Schema->connect(
- $dsn,
- $user,
+ $dsn,
+ $user,
$pass,
{
schema_name_postfix => '_dev'
- # ... Other options as desired ...
+ # ... Other options as desired ...
})
Obviously, one could accomplish even more advanced mapping via a hash map or a
transactions (for databases that support them) will hopefully be added
in the future.
-=head1 SQL
+=head1 SQL
=head2 Creating Schemas From An Existing Database
-L<DBIx::Class::Schema::Loader> will connect to a database and create a
+L<DBIx::Class::Schema::Loader> will connect to a database and create a
L<DBIx::Class::Schema> and associated sources by examining the database.
-The recommend way of achieving this is to use the
+The recommend way of achieving this is to use the
L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method:
perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \
your database.
Make a table class as you would for any other table
-
+
package MyAppDB::Dual;
use strict;
use warnings;
"dummy",
{ data_type => "VARCHAR2", is_nullable => 0, size => 1 },
);
-
+
Once you've loaded your table class select from it using C<select>
and C<as> instead of C<columns>
-
+
my $rs = $schema->resultset('Dual')->search(undef,
{ select => [ 'sydate' ],
as => [ 'now' ]
},
);
-
+
All you have to do now is be careful how you access your resultset, the below
will not work because there is no column called 'now' in the Dual table class
-
+
while (my $dual = $rs->next) {
print $dual->now."\n";
}
# Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23.
-
+
You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to
your Dual class for whatever you wanted to select from dual, but that's just
silly, instead use C<get_column>
-
+
while (my $dual = $rs->next) {
print $dual->get_column('now')."\n";
}
-
+
Or use C<cursor>
-
+
my $cursor = $rs->cursor;
while (my @vals = $cursor->next) {
print $vals[0]."\n";
parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] },
};
$schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args );
-
+
Or use L<DBIx::Class::ResultClass::HashRefInflator>
-
+
$rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
while ( my $dual = $rs->next ) {
print $dual->{now}."\n";
}
-
+
Here are some example C<select> conditions to illustrate the different syntax
-you could use for doing stuff like
+you could use for doing stuff like
C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
-
+
# get a sequence value
select => [ 'A_SEQ.nextval' ],
-
+
# get create table sql
select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
-
+
# get a random num between 0 and 100
select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
-
+
# what year is it?
select => [ { 'extract' => [ \'year from sysdate' ] } ],
-
+
# do some math
select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
-
+
# which day of the week were you born on?
select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
-
+
# select 16 rows from dual
select => [ "'hello'" ],
as => [ 'world' ],
group_by => [ 'cube( 1, 2, 3, 4 )' ],
-
-
+
+
=head2 Adding Indexes And Functions To Your SQL
Often you will want indexes on columns on your table to speed up searching. To
-do this, create a method called C<sqlt_deploy_hook> in the relevant source
-class (refer to the advanced
+do this, create a method called C<sqlt_deploy_hook> in the relevant source
+class (refer to the advanced
L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
to share a hook between multiple sources):
1;
-Sometimes you might want to change the index depending on the type of the
+Sometimes you might want to change the index depending on the type of the
database for which SQL is being generated:
my ($db_type = $sqlt_table->schema->translator->producer_type)
=~ s/^SQL::Translator::Producer:://;
-You can also add hooks to the schema level to stop certain tables being
+You can also add hooks to the schema level to stop certain tables being
created:
package My::Schema;
Alternatively, you can send the conversion sql scripts to your
customers as above.
-=head2 Setting quoting for the generated SQL.
+=head2 Setting quoting for the generated SQL.
If the database contains column names with spaces and/or reserved words, they
need to be quoted in the SQL queries. This is done using:
The first sets the quote characters. Either a pair of matching
brackets, or a C<"> or C<'>:
-
+
__PACKAGE__->storage->sql_maker->quote_char('"');
Check the documentation of your database for the correct quote
characters to use. C<name_sep> needs to be set to allow the SQL
generator to put the quotes the correct place.
-In most cases you should set these as part of the arguments passed to
+In most cases you should set these as part of the arguments passed to
L<DBIx::Class::Schema/connect>:
my $schema = My::Schema->connect(
The JDBC bridge is one way of getting access to a MSSQL server from a platform
that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
-The limit dialect can also be set at connect time by specifying a
+The limit dialect can also be set at connect time by specifying a
C<limit_dialect> key in the final hash as shown above.
=head2 Working with PostgreSQL array types
arrayrefs together with the column name, like this: C<< [column_name => value]
>>.
-=head1 BOOTSTRAPPING/MIGRATING
+=head1 BOOTSTRAPPING/MIGRATING
=head2 Easy migration from class-based to schema-based setup
use MyDB;
use SQL::Translator;
-
+
my $schema = MyDB->schema_instance;
-
- my $translator = SQL::Translator->new(
+
+ my $translator = SQL::Translator->new(
debug => $debug || 0,
trace => $trace || 0,
no_comments => $no_comments || 0,
'prefix' => 'My::Schema',
},
);
-
+
$translator->parser('SQL::Translator::Parser::DBIx::Class');
$translator->producer('SQL::Translator::Producer::DBIx::Class::File');
-
+
my $output = $translator->translate(@args) or die
"Error: " . $translator->error;
-
+
print $output;
You could use L<Module::Find> to search for all subclasses in the MyDB::*
return $new;
}
-For more information about C<next::method>, look in the L<Class::C3>
+For more information about C<next::method>, look in the L<Class::C3>
documentation. See also L<DBIx::Class::Manual::Component> for more
ways to write your own base classes to do this.
People looking for ways to do "triggers" with DBIx::Class are probably
-just looking for this.
+just looking for this.
=head2 Changing one field whenever another changes
-For example, say that you have three columns, C<id>, C<number>, and
+For example, say that you have three columns, C<id>, C<number>, and
C<squared>. You would like to make changes to C<number> and have
C<squared> be automagically set to the value of C<number> squared.
You can accomplish this by overriding C<store_column>:
=head2 Automatically creating related objects
-You might have a class C<Artist> which has many C<CD>s. Further, if you
+You might have a class C<Artist> which has many C<CD>s. Further, you
want to create a C<CD> object every time you insert an C<Artist> object.
You can accomplish this by overriding C<insert> on your objects:
If this preamble is moved into a common base class:-
package MyDBICbase;
-
+
use base qw/DBIx::Class/;
__PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
1;
to load the result classes. This will use L<Module::Find|Module::Find>
to find and load the appropriate modules. Explicitly defining the
classes you wish to load will remove the overhead of
-L<Module::Find|Module::Find> and the related directory operations:-
+L<Module::Find|Module::Find> and the related directory operations:
__PACKAGE__->load_classes(qw/ CD Artist Track /);
projects / dbsrgits/DBIx-Class.git / commitdiff