you've been doing this for a while with L<Class::DBI>, and think there's a
better way? You've come to the right place.
-=head1 THE DBIx::Class WAY
+=head1 THE DBIx::Class WAY (CLIFF NOTES)
Here are a few simple tips that will help you get your bearings with
-DBIx::Class.
+L<DBIC|DBIx::Class>.
=head2 Tables become Result classes
-DBIx::Class needs to know what your Table structure looks like. You
-do that by defining Result classes. Result classes are defined by
-calling methods proxied to L<DBIx::Class::ResultSource>. Each Result
-class defines one Table, which defines the Columns it has, along with
-any Relationships it has to other tables. (And oh, so much more
-besides) The important thing to understand:
+L<DBIC|DBIx::Class> needs to know what your Table structure looks like. You
+do that by defining L<Result classes|DBIx::Class::Manual::ResultClass>. Each
+Result class defines one Table, which defines the Columns it has, any
+L<Relationships|DBIx::Class::Relationship> it has to other tables, and much more.
- A Result class == Table
+The important thing to understand:
+
+ A Result class ~~ Table
(most of the time, but just bear with my simplification)
=head2 It's all about the ResultSet
-So, we've got some ResultSources defined. Now, we want to actually use those
-definitions to help us translate the queries we need into handy perl objects!
-
-Let's say we defined a ResultSource for an "album" table with three columns:
-"albumid", "artist", and "title". Any time we want to query this table, we'll
-be creating a L<DBIx::Class::ResultSet> from its ResultSource. For example, the
-results of:
+Let's say we defined a L<Result class|DBIx::Class::Manual::ResultClass> (called
+C<MyApp::Schema::Result::Artist>) for an C<album> table with three columns:
+C<albumid>, C<artist>, and C<title>. Any time we want to query this table, we'll
+be creating a L<ResultSet|DBIx::Class::ResultSet> from its
+L<Schema|DBIx::Class::Schema>. For example, the results of:
SELECT albumid, artist, title FROM album;
-Would be retrieved by creating a ResultSet object from the album table's
-ResultSource, likely by using the "search" method.
+Would be represented like so:
-DBIx::Class doesn't limit you to creating only simple ResultSets -- if you
+ my $rs = $schema->resultset('Album')->search(undef, {
+ columns => [qw{ albumid artist title }]
+ });
+
+L<DBIC|DBIx::Class> doesn't limit you to creating only simple ResultSets -- if you
wanted to do something like:
SELECT title FROM album GROUP BY title;
-You could easily achieve it.
+You could easily achieve it, like this:
+
+ my $rs = $schema->resultset('Album')->search(undef, {
+ columns => ['title'],
+ group_by => ['title'],
+ });
The important thing to understand:
- Any time you would reach for a SQL query in DBI, you are
- creating a DBIx::Class::ResultSet.
+ Instead of writing SQL queries manually, you ask a ResultSet object to
+ generate them.
-=head2 Search is like "prepare"
+=head2 Search results are returned as "Rows"
-DBIx::Class tends to wait until it absolutely must fetch information from the
-database. If you are returning a ResultSet, the query won't execute until you
-use a method that wants to access the data. (Such as "next", or "first")
+Rows of the search from the database are blessed into
+L<Result objects|DBIx::Class::Manual::ResultClass>. This might seem conflicting,
+but this is because a Result class is supposed to be customizable "toolset" for
+both result management and table definition.
The important thing to understand:
- Setting up a ResultSet does not execute the query; retrieving
- the data does.
+ When -defining- a Result class, the purpose of the class is to:
+ * Define the table, columns, and constraints
+ * Define relationships to other tables
-=head2 Search results are returned as Rows
+ When -using- a Result object, the purpose of the object is to:
+ * Read data from a result (like a row)
+ * Perform CRUD operations, based on that data
+ * "Inflate" columns
+ * Use custom methods defined in the class by you
-Rows of the search from the database are blessed into
-L<DBIx::Class::Row> objects.
+=head2 Search is like "prepare"
+
+L<DBIC|DBIx::Class> tends to wait until it absolutely must fetch information from the
+database. If you are returning a L<ResultSet|DBIx::Class::ResultSet>, the
+query won't execute until you use a method that wants to access the data, such
+as C<next> or C<first>.
+
+ # Does not run any SQL statements yet
+ my $rs = $schema->resultset('Album')->search(undef, {
+ columns => [qw{ albumid artist title }]
+ });
+
+ # Will trigger the SQL query once and loop through the results
+ while (my $result = $rs->next) {
+ my $artist = $result->artist;
+ ...
+ }
=head1 SETTING UP DBIx::Class
-Let's look at how you can set and use your first native L<DBIx::Class> tree.
+Let's look at how you can set and use your first native L<DBIC|DBIx::Class> tree.
+
+=head2 Which deployment method to take
+
+There are a few different ways to create your L<DBIC|DBIx::Class> tree. Which
+recommended method to take depends on how your database currently exists:
+
+ * If you are creating a brand new database, set up the tree manually, and then
+ create the tables via $schema->deploy (or another deployment tool).
+ * If the database already exists, use DBIx::Class::Schema::Loader or another
+ schema builder.
+
+Since L<DBIC|DBIx::Class> first came into the scene, there have been a number of
+useful deployment tools (schema builders) that ease the process (from oldest to
+newest):
+
+=over
+
+=item *
+
+L<DBIx::Class::Schema::Loader> (existing DB only)
+
+=item *
+
+L<DBIx::Class::DeploymentHandler> (new or existing DB)
+
+=item *
-First we'll see how you can set up your classes yourself. If you want them to
-be auto-discovered, just skip to the next section, which shows you how to use
-L<DBIx::Class::Schema::Loader>.
+L<DBIx::Class::Migration> (new or existing DB)
+
+=back
+
+This document only covers the manual method and L<DBICSL|/Using
+DBIx::Class::Schema::Loader>. However, users with complex schemas might want
+to check out the latest deployment tech to make life easier.
=head2 Setting it up manually
+=head3 Schema
+
First, you should create your base schema class, which inherits from
L<DBIx::Class::Schema>:
package My::Schema;
use base qw/DBIx::Class::Schema/;
-In this class you load your result_source ("table", "model") classes, which we
-will define later, using the load_namespaces() method:
+In this class, you load your C<result_source> ("table", "model") classes, which
+we will define later, using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
+method:
# load My::Schema::Result::* and their resultset classes
__PACKAGE__->load_namespaces();
-By default this loads all the Result (Row) classes in the
-My::Schema::Result:: namespace, and also any resultset classes in the
-My::Schema::ResultSet:: namespace (if missing, the resultsets are
-defaulted to be DBIx::Class::ResultSet objects). You can change the
-result and resultset namespaces by using options to the
-L<DBIx::Class::Schema/load_namespaces> call.
+By default, this loads all the L<Result classes|DBIx::Class::Manual::ResultClass>
+in the C<My::Schema::Result::> namespace, and also any ResultSet classes in the
+C<My::Schema::ResultSet::> namespace. (If missing, the ResultSets are
+defaulted to be L<DBIx::Class::ResultSet> objects.) You can change the Result
+and ResultSet namespaces by using options to the
+L<load_namespaces|DBIx::Class::Schema/load_namespaces> call.
It is also possible to do the same things manually by calling
-C<load_classes> for the Row classes and defining in those classes any
-required resultset classes.
+L<load_classes|DBIx::Class::Schema/load_classes> for the
+L<Result classes|DBIx::Class::Manual::ResultClass> and
+defining in those classes any required ResultSet classes.
+
+=head3 Result class
+
+=head4 Header
Next, create each of the classes you want to load as specified above:
package My::Schema::Result::Album;
- use base qw/DBIx::Class/;
+ use base qw/DBIx::Class::Core/;
+
+Load any additional components you may need with the
+L<load_components|Class::C3::Componentised/load_components( @comps )> method,
+and provide component configuration if required. For example, if you want
+automatic row ordering:
-Load any components required by each class with the load_components() method.
-This should consist of "Core" plus any additional components you want to use.
-For example, if you want to force columns to use UTF-8 encoding:
+ __PACKAGE__->load_components(qw/ Ordered /);
+ __PACKAGE__->position_column('rank');
- __PACKAGE__->load_components(qw/ ForceUTF8 Core /);
+(See L<DBIx::Class::Ordered> for more information.)
Set the table for your class:
__PACKAGE__->table('album');
+=head4 Columns
+
Add columns to your class:
- __PACKAGE__->add_columns(qw/ albumid artist title /);
+ __PACKAGE__->add_columns(qw/ albumid artist title rank /);
Each column can also be set up with its own accessor, data_type and other pieces
of information that it may be useful to have -- just pass C<add_columns> a hash:
- __PACKAGE__->add_columns(albumid =>
- { accessor => 'album',
- data_type => 'integer',
- size => 16,
- is_nullable => 0,
- is_auto_increment => 1,
- default_value => '',
- },
- artist =>
- { data_type => 'integer',
- size => 16,
- is_nullable => 0,
- is_auto_increment => 0,
- default_value => '',
- },
- title =>
- { data_type => 'varchar',
- size => 256,
- is_nullable => 0,
- is_auto_increment => 0,
- default_value => '',
- }
- );
-
-DBIx::Class doesn't directly use most of this data yet, but various related
-modules such as L<DBIx::Class::WebForm> make use of it. Also it allows you to
-create your database tables from your Schema, instead of the other way around.
-See L<SQL::Translator> for details.
-
-See L<DBIx::Class::ResultSource> for more details of the possible column
+ __PACKAGE__->add_columns(
+ albumid => {
+ accessor => 'album',
+ data_type => 'integer',
+ size => 16,
+ is_auto_increment => 1,
+ },
+ artist => {
+ data_type => 'integer',
+ size => 16,
+ },
+ title => {
+ data_type => 'varchar',
+ size => 256,
+ is_nullable => 1,
+ },
+ rank => {
+ data_type => 'integer',
+ size => 16,
+ default_value => 0,
+ },
+ );
+
+L<DBIC|DBIx::Class> doesn't directly use most of this data, but various
+related modules, such as L<HTML::FormHandler::Model::DBIC>, make use of it. Also,
+it allows you to create your database tables from your Schema, instead of the
+other way around. See L<DBIx::Class::Schema/deploy> for details.
+
+See L<DBIx::Class::ResultSource/add_columns> for more details of the possible column
attributes.
-Accessors are created for each column automatically, so My::Schema::Result::Album will
-have albumid() (or album(), when using the accessor), artist() and title()
-methods.
+Accessors are created for each column automatically, so C<My::Schema::Result::Album>
+will have C<albumid> (or C<album>, when using the accessor shown above), C<artist>
+and C<title> methods.
+
+=head4 Primary Key
Define a primary key for your class:
__PACKAGE__->set_primary_key( qw/ albumid artistid / );
-Define this class' relationships with other classes using either C<belongs_to>
-to describe a column which contains an ID of another Table, or C<has_many> to
-make a predefined accessor for fetching objects that contain this Table's
-foreign key:
+See also L</The Significance and Importance of Primary Keys>.
+
+=head4 Relationships
+
+Define this class' relationships with other classes to make predefined accessors
+for your L<Result class|DBIx::Class::Manual::ResultClass>. Use either
+L<belongs_to|DBIx::Class::Relationship/belongs_to> to describe columns which
+contain an ID of another Table, or
+L<has_many|DBIx::Class::Relationship/has_many> to fetch objects that contain this
+Table's foreign key:
# in My::Schema::Result::Artist
__PACKAGE__->has_many('albums', 'My::Schema::Result::Album', 'artist');
See L<DBIx::Class::Relationship> for more information about the various types of
available relationships and how you can design your own.
-=head2 Using L<DBIx::Class::Schema::Loader>
+=head2 Using DBIx::Class::Schema::Loader
-This is an external module, and not part of the L<DBIx::Class> distribution.
-Like L<Class::DBI::Loader>, it inspects your database, and automatically creates
-classes for all the tables in your database. Here's a simple setup:
+L<DBICSL|DBIx::Class::Schema::Loader> is an external module, and not part
+of the L<DBIC|DBIx::Class> distribution. It inspects your database, and
+automatically creates classes for all the tables in your schema.
- package My::Schema;
- use base qw/DBIx::Class::Schema::Loader/;
+The simplest way to use it is via the L<dbicdump> script from the
+L<DBIx::Class::Schema::Loader> distribution. For example:
+
+ $ dbicdump -o dump_directory=./lib \
+ -o components='["InflateColumn::DateTime"]' \
+ MyApp::Schema dbi:mysql:mydb user pass
+
+If you have a mixed-case database, use the C<preserve_case> option, e.g.:
- __PACKAGE__->loader_options( relationships => 1 );
+ $ dbicdump -o dump_directory=./lib -o preserve_case=1 \
+ -o components='["InflateColumn::DateTime"]' \
+ MyApp::Schema dbi:mysql:mydb user pass
- 1;
+If you are using L<Catalyst>, then you can use the helper that comes with
+L<Catalyst::Model::DBIC::Schema>:
-The actual autoloading process will occur when you create a connected instance
-of your schema below.
+ $ script/myapp_create.pl model MyDB DBIC::Schema MyDB::Schema \
+ create=static moniker_map='{ foo => "FOO" }' dbi:SQLite:./myapp.db \
+ on_connect_do='PRAGMA foreign_keys=ON' quote_char='"'
-See the L<DBIx::Class::Schema::Loader> documentation for more information on its
-many options.
+See L<Catalyst::Helper::Model::DBIC::Schema> for more information on this
+helper.
+
+See the L<DBIx::Class::Schema::Loader> and L<DBIx::Class::Schema::Loader::Base>
+documentation for more information on the many loader options.
=head2 Connecting
-To connect to your Schema, you need to provide the connection details. The
-arguments are the same as for L<DBI/connect>:
+To connect to your Schema, you need to provide the connection details or a
+database handle.
+
+=head3 Via connection details
+
+The arguments are the same as for L<DBI/connect>:
my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db');
Note that L<DBIx::Class::Schema> does not cache connections for you. If you use
multiple connections, you need to do this manually.
-To execute some sql statements on every connect you can add them as an option in
+To execute some SQL statements on every connect you can add them as an option in
a special fifth argument to connect:
my $another_schema = My::Schema->connect(
{ on_connect_do => \@on_connect_sql_statments }
);
-See L<DBIx::Class::Schema::Storage::DBI/connect_info> for more information about
+See L<DBIx::Class::Storage::DBI/connect_info> for more information about
this and other special C<connect>-time options.
+=head3 Via a database handle
+
+The supplied coderef is expected to return a single connected database handle
+(e.g. a L<DBI> C<$dbh>)
+
+ my $schema = My::Schema->connect (
+ sub { Some::DBH::Factory->connect },
+ \%extra_attrs,
+ );
+
=head2 Basic usage
Once you've defined the basic classes, either manually or using
$album->set_column('title', 'Presence');
$title = $album->get_column('title');
-Just like with L<Class::DBI>, you call C<update> to commit your changes to the
-database:
+Just like with L<Class::DBI>, you call C<update> to save your changes to the
+database (by executing the actual C<UPDATE> statement):
$album->update;
=head2 Finding your objects
-L<DBIx::Class> provides a few different ways to retrieve data from your
+L<DBIC|DBIx::Class> provides a few different ways to retrieve data from your
database. Here's one example:
# Find all of Santana's albums
my @albums = My::Schema->resultset('Album')->search(
{ artist => 'Bob Marley' },
- { rows => 2, order_by => 'year DESC' }
+ { rows => 2, order_by => { -desc => 'year' } }
);
C<@albums> then holds the two most recent Bob Marley albums.
=head1 NOTES
+=head2 The Significance and Importance of Primary Keys
+
+The concept of a L<primary key|DBIx::Class::ResultSource/set_primary_key> in
+L<DBIC|DBIx::Class> warrants special discussion. The formal definition (which somewhat
+resembles that of a classic RDBMS) is I<a unique constraint that is least
+likely to change after initial row creation>. However, this is where the
+similarity ends. Any time you call a CRUD operation on a row (e.g.
+L<delete|DBIx::Class::Row/delete>,
+L<update|DBIx::Class::Row/update>,
+L<discard_changes|DBIx::Class::Row/discard_changes>,
+etc.), L<DBIC|DBIx::Class> will use the values of of the
+L<primary key|DBIx::Class::ResultSource/set_primary_key> columns to populate
+the C<WHERE> clause necessary to accomplish the operation. This is why it is
+important to declare a L<primary key|DBIx::Class::ResultSource/set_primary_key>
+on all your result sources B<even if the underlying RDBMS does not have one>.
+In a pinch, one can always declare each row identifiable by all its columns:
+
+ __PACKAGE__->set_primary_key(__PACKAGE__->columns);
+
+Note that L<DBIC|DBIx::Class> is smart enough to store a copy of the PK values before
+any row-object changes take place, so even if you change the values of PK
+columns, the C<WHERE> clause will remain correct.
+
+If you elect not to declare a C<primary key>, L<DBIC|DBIx::Class> will behave correctly
+by throwing exceptions on any row operation that relies on unique identifiable
+rows. If you inherited datasets with multiple identical rows in them, you can
+still operate with such sets provided you only utilize
+L<DBIx::Class::ResultSet> CRUD methods:
+L<search|DBIx::Class::ResultSet/search>,
+L<update|DBIx::Class::ResultSet/update>,
+L<delete|DBIx::Class::ResultSet/delete>
+
+For example, the following would not work (assuming C<People> does not have
+a declared PK):
+
+ my $row = $schema->resultset('People')
+ ->search({ last_name => 'Dantes' })
+ ->next;
+ $row->update({ children => 2 }); # <-- exception thrown because $row isn't
+ # necessarily unique
+
+So, instead the following should be done:
+
+ $schema->resultset('People')
+ ->search({ last_name => 'Dantes' })
+ ->update({ children => 2 }); # <-- update's ALL Dantes to have children of 2
+
=head2 Problems on RHEL5/CentOS5
There used to be an issue with the system perl on Red Hat Enterprise
=item * L<DBIx::Class::Manual::Cookbook>
+=item * L<DBIx::Class::Manual::ResultClass>
+
=back
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff