DBIx::Class::Manual::Cookbook - Miscellaneous recipes
-=head1 RECIPES
+=head1 SEARCHING
-=head2 Searching
-
-=head3 Paged results
+=head2 Paged results
When you expect a large number of results, you can ask L<DBIx::Class> for a
-paged resultset, which will fetch only a small number of records at a time:
+paged resultset, which will fetch only a defined number of records at a time:
my $rs = $schema->resultset('Artist')->search(
undef,
return $rs->page(1); # DBIx::Class::ResultSet containing first 10 records
-In either of the above cases, you can return a L<Data::Page> object for the
+In either of the above cases, you can get a L<Data::Page> object for the
resultset (suitable for use in e.g. a template) using the C<pager> method:
return $rs->pager();
-=head3 Complex WHERE clauses
+=head2 Complex WHERE clauses
Sometimes you need to formulate a query using specific operators:
For more information on generating complex queries, see
L<SQL::Abstract/WHERE CLAUSES>.
-=head3 Using specific columns
+=head2 Retrieve one and only one row from a resultset
+
+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.
+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.
+
+Before replacing all your calls to C<first()> with C<single()> please observe the
+following CAVEATS:
+
+=over
+
+=item *
+While single() takes a search condition just like search() does, it does
+_not_ accept search attributes. However one can always chain a single() to
+a search():
+
+ my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single;
+
+
+=item *
+Since single() is the engine behind find(), it is designed to fetch a
+single row per database query. Thus a warning will be issued when the
+underlying SELECT returns more than one row. Sometimes however this usage
+is valid: i.e. we have an arbitrary number of cd's but only one of them is
+at the top of the charts at any given time. If you know what you are doing,
+you can silence the warning by explicitly limiting the resultset size:
+
+ my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single;
+
+=back
+
+=head2 Arbitrary SQL through a custom ResultSource
+
+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
+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::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
+ WHERE 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
+
+ # 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( {},
+ {
+ 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).
+
+If you prefer to have the definitions of these custom ResultSources in separate
+files (instead of stuffing all of them into the same resultset class), you can
+achieve the same with subclassing the resultset class and defining the
+ResultSource there:
+
+ package My::Schema::UserFriendsComplex;
+
+ use My::Schema::User;
+ use base qw/My::Schema::User/;
+
+ __PACKAGE__->table('dummy'); # currently must be called before anything else
+
+ # 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!
+ __PACKAGE__->name( \<<SQL );
+ ( 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
+ WHERE f.user_id = ? )
+ SQL
+
+TIMTOWDI.
+
+=head2 Using specific columns
When you only want specific columns from a table, you can use
C<columns> to specify which ones you need. This is useful to avoid
This is a shortcut for C<select> and C<as>, see below. C<columns>
cannot be used together with C<select> and C<as>.
-=head3 Using database functions or stored procedures
+=head2 Using database functions or stored procedures
The combination of C<select> and C<as> can be used to return the result of a
database function or stored procedure as a column value. You use C<select> to
# Or use DBIx::Class::AccessorGroup:
__PACKAGE__->mk_group_accessors('column' => 'name_length');
-=head3 SELECT DISTINCT with multiple columns
+=head2 SELECT DISTINCT with multiple columns
my $rs = $schema->resultset('Foo')->search(
{},
}
);
- my $count = $rs->next->get_column('count');
-
-=head3 SELECT COUNT(DISTINCT colname)
+=head2 SELECT COUNT(DISTINCT colname)
my $rs = $schema->resultset('Foo')->search(
{},
}
);
-=head3 Grouping results
+ my $count = $rs->next->get_column('count');
+
+=head2 Grouping results
L<DBIx::Class> supports C<GROUP BY> as follows:
{},
{
join => [qw/ cds /],
- select => [ 'name', { count => 'cds.cdid' } ],
+ select => [ 'name', { count => 'cds.id' } ],
as => [qw/ name cd_count /],
group_by => [qw/ name /]
}
);
# Equivalent SQL:
- # SELECT name, COUNT( cds.cdid ) FROM artist me
- # LEFT JOIN cd cds ON ( cds.artist = me.artistid )
+ # SELECT name, COUNT( cd.id ) FROM artist
+ # LEFT JOIN cd ON artist.id = cd.artist
# GROUP BY name
Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you
are in any way unsure about the use of the attributes above (C< join
>, C< select >, C< as > and C< group_by >).
-=head3 Predefined searches
+=head2 Subqueries
+
+You can write subqueries relatively easily in DBIC.
+
+ my $inside_rs = $schema->resultset('Artist')->search({
+ name => [ 'Billy Joel', 'Brittany Spears' ],
+ });
+
+ my $rs = $schema->resultset('CD')->search({
+ artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
+ });
+
+The usual operators ( =, !=, IN, NOT IN, etc) are supported.
+
+B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
+The following will B<not> work:
+
+ my $rs = $schema->resultset('CD')->search({
+ artist_id => $inside_rs->get_column('id')->as_query,
+ });
+
+=head3 Correlated subqueries
+
+ my $cdrs = $schema->resultset('CD');
+ my $rs = $cdrs->search({
+ year => {
+ '=' => $cdrs->search(
+ { artistid => { '=' => \'me.artistid' } },
+ { alias => 'inner' }
+ )->get_column('year')->max_rs->as_query,
+ },
+ });
+
+That creates the following SQL:
+
+ SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
+ FROM cd me
+ WHERE year = (
+ SELECT MAX(inner.year)
+ FROM cd inner
+ WHERE artistid = me.artistid
+ )
+
+=head2 Where subqueries will work
+
+Currently, subqueries will B<only> work in the where-clause of a search. In
+other words, in the first hashref of a search() method. Work is being done
+to make them work as part of the second hashref (from, select, +select, etc).
+
+=head2 Predefined searches
You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
and define often used searches as methods:
To use your resultset, first tell DBIx::Class to create an instance of it
for you, in your My::DBIC::Schema::CD class:
+ # class definition as normal
+ __PACKAGE__->load_components(qw/ Core /);
+ __PACKAGE__->table('cd');
+
+ # tell DBIC to use the custom ResultSet class
__PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
+Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods.
+
Then call your new method in your code:
my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+=head2 Using SQL functions on the left hand side of a comparison
-=head3 Predefined searches without writing a ResultSet class
+Using SQL functions on the left hand side of a comparison is generally
+not a good idea since it requires a scan of the entire table. However,
+it can be accomplished with C<DBIx::Class> when necessary.
-Alternatively you can automatically generate a DBIx::Class::ResultSet
-class by using the ResultSetManager component and tagging your method
-as ResultSet:
+If you do not have quoting on, simply include the function in your search
+specification as you would any column:
- __PACKAGE__->load_components(qw/ ResultSetManager Core /);
+ $rs->search({ 'YEAR(date_of_birth)' => 1979 });
- sub search_cds_ordered : ResultSet {
- my ($self) = @_;
- return $self->search(
- {},
- { order_by => 'name DESC' },
- );
- }
+With quoting on, or for a more portable solution, use the C<where>
+attribute:
-Then call your method in the same way from your code:
+ $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
- my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+=begin hidden
+
+(When the bind args ordering bug is fixed, this technique will be better
+and can replace the one above.)
+
+With quoting on, or for a more portable solution, use the C<where> and
+C<bind> attributes:
+
+ $rs->search({}, {
+ where => \'YEAR(date_of_birth) = ?',
+ bind => [ 1979 ]
+ });
+
+=end hidden
+
+=head1 JOINS AND PREFETCHING
=head2 Using joins and prefetch
'artist.name' => 'Bob Marley'
},
{
- join => [qw/artist/], # join the artist table
+ join => 'artist', # join the artist table
}
);
'artist.name' => 'Bob Marley'
},
{
- join => [qw/ artist /],
+ join => 'artist',
order_by => [qw/ artist.name /]
}
- };
+ );
# Equivalent SQL:
# SELECT cd.* FROM cd
'artist.name' => 'Bob Marley'
},
{
- join => [qw/ artist /],
+ join => 'artist',
order_by => [qw/ artist.name /],
- prefetch => [qw/ artist /] # return artist data too!
+ prefetch => 'artist' # return artist data too!
}
);
definitely use data from a related table. Pre-fetching related tables when you
only need columns from the main table will make performance worse!
-=head3 Multi-step joins
+=head2 Multiple joins
+
+In the examples above, the C<join> attribute was a scalar. If you
+pass an array reference instead, you can join to multiple tables. In
+this example, we want to limit the search further, using
+C<LinerNotes>:
+
+ # Relationships defined elsewhere:
+ # CD->belongs_to('artist' => 'Artist');
+ # CD->has_one('liner_notes' => 'LinerNotes', 'cd');
+ my $rs = $schema->resultset('CD')->search(
+ {
+ 'artist.name' => 'Bob Marley'
+ 'liner_notes.notes' => { 'like', '%some text%' },
+ },
+ {
+ join => [qw/ artist liner_notes /],
+ order_by => [qw/ artist.name /],
+ }
+ );
+
+ # Equivalent SQL:
+ # SELECT cd.*, artist.*, liner_notes.* FROM cd
+ # JOIN artist ON cd.artist = artist.id
+ # JOIN liner_notes ON cd.id = liner_notes.cd
+ # WHERE artist.name = 'Bob Marley'
+ # ORDER BY artist.name
+
+=head2 Multi-step joins
Sometimes you want to join more than one relationship deep. In this example,
we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes>
# Equivalent SQL:
# SELECT artist.* FROM artist
- # JOIN ( cd ON artist.id = cd.artist )
- # JOIN ( liner_notes ON cd.id = liner_notes.cd )
+ # LEFT JOIN cd ON artist.id = cd.artist
+ # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
# WHERE liner_notes.notes LIKE '%some text%'
Joins can be nested to an arbitrary level. So if we decide later that we
# Equivalent SQL:
# SELECT artist.* FROM artist
- # JOIN ( cd ON artist.id = cd.artist )
- # JOIN ( liner_notes ON cd.id = liner_notes.cd )
- # JOIN ( author ON author.id = liner_notes.author )
+ # LEFT JOIN cd ON artist.id = cd.artist
+ # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
+ # LEFT JOIN author ON author.id = liner_notes.author
# WHERE liner_notes.notes LIKE '%some text%'
# AND author.name = 'A. Writer'
+=head2 Multi-step and multiple joins
+
+With various combinations of array and hash references, you can join
+tables in any combination you desire. For example, to join Artist to
+CD and Concert, and join CD to LinerNotes:
+
+ # Relationships defined elsewhere:
+ # Artist->has_many('concerts' => 'Concert', 'artist');
+
+ my $rs = $schema->resultset('Artist')->search(
+ { },
+ {
+ join => [
+ {
+ cds => 'liner_notes'
+ },
+ 'concerts'
+ ],
+ }
+ );
+
+ # Equivalent SQL:
+ # SELECT artist.* FROM artist
+ # LEFT JOIN cd ON artist.id = cd.artist
+ # LEFT JOIN liner_notes ON cd.id = liner_notes.cd
+ # LEFT JOIN concert ON artist.id = concert.artist
+
=head2 Multi-step prefetch
From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
# Equivalent SQL:
# SELECT tag.*, cd.*, artist.* FROM tag
- # JOIN cd ON tag.cd = cd.cdid
- # JOIN artist ON cd.artist = artist.artistid
+ # JOIN cd ON tag.cd = cd.id
+ # JOIN artist ON cd.artist = artist.id
Now accessing our C<cd> and C<artist> relationships does not need additional
SQL statements:
my $tag = $rs->first;
print $tag->cd->artist->name;
-=head2 Columns of data
-
-If you want to find the sum of a particular column there are several
-ways, the obvious one is to use search:
-
- my $rs = $schema->resultset('Items')->search(
- {},
- {
- select => [ { sum => 'Cost' } ],
- as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
- }
- );
- my $tc = $rs->first->get_column('total_cost');
-
-Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
-returned when you ask the C<ResultSet> for a column using
-C<get_column>:
-
- my $cost = $schema->resultset('Items')->get_column('Cost');
- my $tc = $cost->sum;
-
-With this you can also do:
-
- my $minvalue = $cost->min;
- my $maxvalue = $cost->max;
-
-Or just iterate through the values of this column only:
-
- while ( my $c = $cost->next ) {
- print $c;
- }
-
- foreach my $c ($cost->all) {
- print $c;
- }
-
-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:
-
- my $avg = $cost->func('AVERAGE');
-
-This will cause the following SQL statement to be run:
-
- SELECT AVERAGE(Cost) FROM Items me
-
-Which will of course only work if your database supports this function.
-See L<DBIx::Class::ResultSetColumn> for more documentation.
-
-=head2 Using relationships
-
-=head3 Create a new row in a related table
-
- my $book->create_related('author', { name => 'Fred'});
-
-=head3 Search in a related table
-
-Only searches for books named 'Titanic' by the author in $author.
-
- my $author->search_related('books', { name => 'Titanic' });
-
-=head3 Delete data in a related table
-
-Deletes only the book named Titanic by the author in $author.
-
- my $author->delete_related('books', { name => 'Titanic' });
-
-=head3 Ordering a relationship result set
-
-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.
-
- Book->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
-
-
-
-=head2 Transactions
-
-As of version 0.04001, there is improved transaction support in
-L<DBIx::Class::Storage::DBI> and L<DBIx::Class::Schema>. Here is an
-example of the recommended way to use it:
-
- my $genus = $schema->resultset('Genus')->find(12);
-
- my $coderef2 = sub {
- $genus->extinct(1);
- $genus->update;
- };
-
- my $coderef1 = sub {
- $genus->add_to_species({ name => 'troglodyte' });
- $genus->wings(2);
- $genus->update;
- $schema->txn_do($coderef2); # Can have a nested transaction
- return $genus->species;
- };
-
- my $rs;
- eval {
- $rs = $schema->txn_do($coderef1);
- };
-
- if ($@) { # Transaction failed
- die "the sky is falling!" #
- if ($@ =~ /Rollback failed/); # Rollback failed
-
- deal_with_failed_transaction();
- }
-
-Nested transactions will work as expected. That is, only the outermost
-transaction will actually issue a commit to the $dbh, and a rollback
-at any level of any transaction will cause the entire nested
-transaction to fail. Support for savepoints and for true nested
-transactions (for databases that support them) will hopefully be added
-in the future.
-
-=head2 Many-to-many relationships
-
-This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
-
- package My::DB;
- # ... set up connection ...
+=head1 ROW-LEVEL OPERATIONS
- package My::User;
- use base 'My::DB';
- __PACKAGE__->table('user');
- __PACKAGE__->add_columns(qw/id name/);
- __PACKAGE__->set_primary_key('id');
- __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
- __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
-
- package My::UserAddress;
- use base 'My::DB';
- __PACKAGE__->table('user_address');
- __PACKAGE__->add_columns(qw/user address/);
- __PACKAGE__->set_primary_key(qw/user address/);
- __PACKAGE__->belongs_to('user' => 'My::User');
- __PACKAGE__->belongs_to('address' => 'My::Address');
-
- package My::Address;
- use base 'My::DB';
- __PACKAGE__->table('address');
- __PACKAGE__->add_columns(qw/id street town area_code country/);
- __PACKAGE__->set_primary_key('id');
- __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
- __PACKAGE__->many_to_many('users' => 'user_address', 'user');
+=head2 Retrieving a row object's Schema
- $rs = $user->addresses(); # get all addresses for a user
- $rs = $address->users(); # get all users for an address
+It is possible to get a Schema object from a row object like so:
-=head2 Setting default values for a row
+ my $schema = $cd->result_source->schema;
+ # use the schema as normal:
+ my $artist_rs = $schema->resultset('Artist');
-It's as simple as overriding the C<new> method. Note the use of
-C<next::method>.
+This can be useful when you don't want to pass around a Schema object to every
+method.
- sub new {
- my ( $class, $attrs ) = @_;
+=head2 Getting the value of the primary key for the last database insert
- $attrs->{foo} = 'bar' unless defined $attrs->{foo};
+AKA getting last_insert_id
- $class->next::method($attrs);
- }
+If you are using PK::Auto (which is a core component as of 0.07), this is
+straightforward:
-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.
+ my $foo = $rs->create(\%blah);
+ # do more stuff
+ my $id = $foo->id; # foo->my_primary_key_field will also work.
-People looking for ways to do "triggers" with DBIx::Class are probably
-just looking for this.
+If you are not using autoincrementing primary keys, this will probably
+not work, but then you already know the value of the last primary key anyway.
=head2 Stringification
return $self->Description;
}, fallback => 1;
-=head2 Disconnecting cleanly
+=head2 Want to know if find_or_create found or created a row?
-If you find yourself quitting an app with Control-C a lot during
-development, you might like to put the following signal handler in
-your main database class to make sure it disconnects cleanly:
-
- $SIG{INT} = sub {
- __PACKAGE__->storage->disconnect;
- };
+Just use C<find_or_new> instead, then check C<in_storage>:
-=head2 Schema import/export
+ my $obj = $rs->find_or_new({ blah => 'blarg' });
+ unless ($obj->in_storage) {
+ $obj->insert;
+ # do whatever else you wanted if it was a new row
+ }
-This functionality requires you to have L<SQL::Translator> (also known as
-"SQL Fairy") installed.
+=head2 Dynamic Sub-classing DBIx::Class proxy classes
-To create a DBIx::Class schema from an existing database:
+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
+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
+this.
- sqlt --from DBI
- --to DBIx::Class::File
- --prefix "MySchema" > MySchema.pm
+Overriding the C<inflate_result> method within the User proxy-class
+gives us the effect we want. This method is called by
+L<DBIx::Class::ResultSet> when inflating a result from storage. So we
+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 DB::Schema;
+
+ use base qw/DBIx::Class::Schema/;
+
+ __PACKAGE__->load_classes(qw/User/);
+
+
+B<Proxy-Class definitions>
+
+ package DB::Schema::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 ;
+ }
+
+
+ package DB::Schema::User::Admin;
+
+ use strict;
+ use warnings;
+ use base qw/DB::Schema::User/;
+
+ sub hello
+ {
+ print "I am an admin.\n";
+ return;
+ }
+
+ sub do_admin_stuff
+ {
+ print "I am doing admin stuff\n";
+ return ;
+ }
+
+B<Test File> test.pl
+
+ use warnings;
+ use strict;
+ use DB::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 = DB::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');
-To create a MySQL database from an existing L<DBIx::Class> schema, convert the
-schema to MySQL's dialect of SQL:
+=head2 Skip row object creation for faster results
- sqlt --from SQL::Translator::Parser::DBIx::Class
- --to MySQL
- --DBIx::Class "MySchema.pm" > Schema1.sql
+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>.
-And import using the mysql client:
+ my $rs = $schema->resultset('CD');
+
+ $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
+
+ my $hash_ref = $rs->find(1);
- mysql -h "host" -D "database" -u "user" -p < Schema1.sql
+Wasn't that easy?
-=head2 Easy migration from class-based to schema-based setup
+=head2 Get raw data for blindingly fast results
-You want to start using the schema-based approach to L<DBIx::Class>
-(see L<SchemaIntro.pod>), but have an established class-based setup with lots
-of existing classes that you don't want to move by hand. Try this nifty script
+If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution
+above is not fast enough for you, you can use a DBIx::Class to return values
+exactly as they come out of the data base with none of the convenience methods
+wrapped round them.
+
+This is used like so:
+
+ my $cursor = $rs->cursor
+ while (my @vals = $cursor->next) {
+ # use $val[0..n] here
+ }
+
+You will need to map the array offsets to particular columns (you can
+use the I<select> attribute of C<search()> to force ordering).
+
+=head1 RESULTSET OPERATIONS
+
+=head2 Getting Schema from a ResultSet
+
+To get the schema object from a result set, do the following:
+
+ $rs->result_source->schema
+
+=head2 Getting Columns Of Data
+
+AKA Aggregating Data
+
+If you want to find the sum of a particular column there are several
+ways, the obvious one is to use search:
+
+ my $rs = $schema->resultset('Items')->search(
+ {},
+ {
+ select => [ { sum => 'Cost' } ],
+ as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
+ }
+ );
+ my $tc = $rs->first->get_column('total_cost');
+
+Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets
+returned when you ask the C<ResultSet> for a column using
+C<get_column>:
+
+ my $cost = $schema->resultset('Items')->get_column('Cost');
+ my $tc = $cost->sum;
+
+With this you can also do:
+
+ my $minvalue = $cost->min;
+ my $maxvalue = $cost->max;
+
+Or just iterate through the values of this column only:
+
+ while ( my $c = $cost->next ) {
+ print $c;
+ }
+
+ foreach my $c ($cost->all) {
+ print $c;
+ }
+
+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:
- use MyDB;
- use SQL::Translator;
-
- my $schema = MyDB->schema_instance;
-
- my $translator = SQL::Translator->new(
- debug => $debug || 0,
- trace => $trace || 0,
- no_comments => $no_comments || 0,
- show_warnings => $show_warnings || 0,
- add_drop_table => $add_drop_table || 0,
- validate => $validate || 0,
- parser_args => {
- 'DBIx::Schema' => $schema,
- },
- producer_args => {
- 'prefix' => 'My::Schema',
- },
+ my $avg = $cost->func('AVERAGE');
+
+This will cause the following SQL statement to be run:
+
+ SELECT AVERAGE(Cost) FROM Items me
+
+Which will of course only work if your database supports this function.
+See L<DBIx::Class::ResultSetColumn> for more documentation.
+
+=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
+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:
+
+ my @uploadable_groups;
+ while (my $group = $groups->next) {
+ if ($group->can_upload($self)) {
+ push @uploadable_groups, $group;
+ }
+ }
+ my $new_rs = $self->result_source->resultset;
+ $new_rs->set_cache(\@uploadable_groups);
+ return $new_rs;
+
+
+=head1 USING RELATIONSHIPS
+
+=head2 Create a new row in a related table
+
+ my $author = $book->create_related('author', { name => 'Fred'});
+
+=head2 Search in a related table
+
+Only searches for books named 'Titanic' by the author in $author.
+
+ my $books_rs = $author->search_related('books', { name => 'Titanic' });
+
+=head2 Delete data in a related table
+
+Deletes only the book named Titanic by the author in $author.
+
+ $author->delete_related('books', { name => 'Titanic' });
+
+=head2 Ordering a relationship result set
+
+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
+as follows:
+
+ __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
+
+=head2 Filtering a relationship result set
+
+If you want to get a filtered result set, you can just add add to $attr as follows:
+
+ __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
+
+=head2 Many-to-many relationships
+
+This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
+
+ package My::User;
+ use base 'DBIx::Class';
+ __PACKAGE__->load_components('Core');
+ __PACKAGE__->table('user');
+ __PACKAGE__->add_columns(qw/id name/);
+ __PACKAGE__->set_primary_key('id');
+ __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user');
+ __PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
+
+ package My::UserAddress;
+ use base 'DBIx::Class';
+ __PACKAGE__->load_components('Core');
+ __PACKAGE__->table('user_address');
+ __PACKAGE__->add_columns(qw/user address/);
+ __PACKAGE__->set_primary_key(qw/user address/);
+ __PACKAGE__->belongs_to('user' => 'My::User');
+ __PACKAGE__->belongs_to('address' => 'My::Address');
+
+ package My::Address;
+ use base 'DBIx::Class';
+ __PACKAGE__->load_components('Core');
+ __PACKAGE__->table('address');
+ __PACKAGE__->add_columns(qw/id street town area_code country/);
+ __PACKAGE__->set_primary_key('id');
+ __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address');
+ __PACKAGE__->many_to_many('users' => 'user_address', 'user');
+
+ $rs = $user->addresses(); # get all addresses for a user
+ $rs = $address->users(); # get all users for an address
+
+=head1 TRANSACTIONS
+
+As of version 0.04001, there is improved transaction support in
+L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an
+example of the recommended way to use it:
+
+ my $genus = $schema->resultset('Genus')->find(12);
+
+ my $coderef2 = sub {
+ $genus->extinct(1);
+ $genus->update;
+ };
+
+ my $coderef1 = sub {
+ $genus->add_to_species({ name => 'troglodyte' });
+ $genus->wings(2);
+ $genus->update;
+ $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit
+ return $genus->species;
+ };
+
+ my $rs;
+ eval {
+ $rs = $schema->txn_do($coderef1);
+ };
+
+ if ($@) { # Transaction failed
+ die "the sky is falling!" #
+ if ($@ =~ /Rollback failed/); # Rollback failed
+
+ deal_with_failed_transaction();
+ }
+
+Nested transactions will work as expected. That is, only the outermost
+transaction will actually issue a commit to the $dbh, and a rollback
+at any level of any transaction will cause the entire nested
+transaction to fail. Support for savepoints and for true nested
+transactions (for databases that support them) will hopefully be added
+in the future.
+
+=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> and associated sources by examining the database.
+
+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 \
+ -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])'
+
+This will create a tree of files rooted at C<./lib/My/Schema/> containing
+source definitions for all the tables found in the C<foo> database.
+
+=head2 Creating DDL SQL
+
+The following functionality requires you to have L<SQL::Translator>
+(also known as "SQL Fairy") installed.
+
+To create a set of database-specific .sql files for the above schema:
+
+ my $schema = My::Schema->connect($dsn);
+ $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
+ '0.1',
+ './dbscriptdir/'
+ );
+
+By default this will create schema files in the current directory, for
+MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm.
+
+To create a new database using the schema:
+
+ my $schema = My::Schema->connect($dsn);
+ $schema->deploy({ add_drop_tables => 1});
+
+To import created .sql files using the mysql client:
+
+ mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
+
+To create C<ALTER TABLE> conversion scripts to update a database to a
+newer version of your schema at a later point, first set a new
+C<$VERSION> in your Schema file, then:
+
+ my $schema = My::Schema->connect($dsn);
+ $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'],
+ '0.2',
+ '/dbscriptdir/',
+ '0.1'
+ );
+
+This will produce new database-specific .sql files for the new version
+of the schema, plus scripts to convert from version 0.1 to 0.2. This
+requires that the files for 0.1 as created above are available in the
+given directory to diff against.
+
+=head2 Select from dual
+
+Dummy tables are needed by some databases to allow calling functions
+or expressions that aren't based on table content, for examples of how
+this applies to various database types, see:
+L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>.
+
+Note: If you're using Oracles dual table don't B<ever> do anything
+other than a select, if you CRUD on your dual table you *will* break
+your database.
+
+Make a table class as you would for any other table
+
+ package MyAppDB::Dual;
+ use strict;
+ use warnings;
+ use base 'DBIx::Class';
+ __PACKAGE__->load_components("Core");
+ __PACKAGE__->table("Dual");
+ __PACKAGE__->add_columns(
+ "dummy",
+ { data_type => "VARCHAR2", is_nullable => 0, size => 1 },
);
-
- $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;
+
+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";
+ }
+
+Or use L<DBIx::Class::ResultClass::HashRefInflator>
+
+ $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
+ while ( my $dual = $rs->next ) {
+ print $dual->{now}."\n";
+ }
+
+Here are some example C<select> conditions to illustrate the different syntax
+you could use for doing stuff like
+C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')>
+
+ # get a sequence value
+ select => [ 'A_SEQ.nextval' ],
+
+ # get create table sql
+ select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ],
+
+ # get a random num between 0 and 100
+ select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ],
+
+ # what year is it?
+ select => [ { 'extract' => [ \'year from sysdate' ] } ],
+
+ # do some math
+ select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}],
+
+ # which day of the week were you born on?
+ select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}],
+
+ # select 16 rows from dual
+ select => [ "'hello'" ],
+ as => [ 'world' ],
+ group_by => [ 'cube( 1, 2, 3, 4 )' ],
+
+
+
+=head2 Adding Indexes And Functions To Your SQL
+
+Often you will want indexes on columns on your table to speed up searching. To
+do this, create a method called C<sqlt_deploy_hook> in the relevant source
+class (refer to the advanced
+L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish
+to share a hook between multiple sources):
+
+ package My::Schema::Artist;
+
+ __PACKAGE__->table('artist');
+ __PACKAGE__->add_columns(id => { ... }, name => { ... })
+
+ sub sqlt_deploy_hook {
+ my ($self, $sqlt_table) = @_;
+
+ $sqlt_table->add_index(name => 'idx_name', fields => ['name']);
+ }
+
+ 1;
+
+Sometimes you might want to change the index depending on the type of the
+database for which SQL is being generated:
+
+ my ($db_type = $sqlt_table->schema->translator->producer_type)
+ =~ s/^SQL::Translator::Producer:://;
+
+You can also add hooks to the schema level to stop certain tables being
+created:
+
+ package My::Schema;
+
+ ...
+
+ sub sqlt_deploy_hook {
+ my ($self, $sqlt_schema) = @_;
+
+ $sqlt_schema->drop_table('table_name');
+ }
+
+You could also add views, procedures or triggers to the output using
+L<SQL::Translator::Schema/add_view>,
+L<SQL::Translator::Schema/add_procedure> or
+L<SQL::Translator::Schema/add_trigger>.
-You could use L<Module::Find> to search for all subclasses in the MyDB::*
-namespace, which is currently left as an exercise for the reader.
=head2 Schema versioning
=back
-=head3 Create a DBIx::Class schema
+B<Create a DBIx::Class schema>
This can either be done manually, or generated from an existing database as
-described under C<Schema import/export>.
+described under L</Creating Schemas From An Existing Database>
-=head3 Save the schema
+B<Save the schema>
-Use C<sqlt> to transform your schema into an SQL script suitable for your
-customer's database. E.g. for MySQL:
+Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>.
- sqlt --from SQL::Translator::Parser::DBIx::Class
- --to MySQL
- --DBIx::Class "MySchema.pm" > Schema1.mysql.sql
-
-If you need to target databases from multiple vendors, just generate an SQL
-script suitable for each. To support PostgreSQL too:
-
- sqlt --from SQL::Translator::DBIx::Class
- --to PostgreSQL
- --DBIx::Class "MySchema.pm" > Schema1.pgsql.sql
-
-=head3 Deploy to customers
+B<Deploy to customers>
There are several ways you could deploy your schema. These are probably
beyond the scope of this recipe, but might include:
=back
-=head3 Modify the schema to change functionality
+B<Modify the schema to change functionality>
+
+As your application evolves, it may be necessary to modify your schema
+to change functionality. Once the changes are made to your schema in
+DBIx::Class, export the modified schema and the conversion scripts as
+in L</Creating DDL SQL>.
+
+B<Deploy update to customers>
+
+Add the L<DBIx::Class::Schema::Versioned> schema component to your
+Schema class. This will add a new table to your database called
+C<dbix_class_schema_vesion> which will keep track of which version is installed
+and warn if the user trys to run a newer schema version than the
+database thinks it has.
+
+Alternatively, you can send the conversion sql scripts to your
+customers as above.
+
+=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:
+
+ __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
+ __PACKAGE__->storage->sql_maker->name_sep('.');
+
+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
+L<DBIx::Class::Schema/connect>:
+
+ my $schema = My::Schema->connect(
+ 'dbi:mysql:my_db',
+ 'db_user',
+ 'db_password',
+ {
+ quote_char => '"',
+ name_sep => '.'
+ }
+ )
+
+=head2 Setting limit dialect for SQL::Abstract::Limit
+
+In some cases, SQL::Abstract::Limit cannot determine the dialect of
+the remote SQL server by looking at the database handle. This is a
+common problem when using the DBD::JDBC, since the DBD-driver only
+know that in has a Java-driver available, not which JDBC driver the
+Java component has loaded. This specifically sets the limit_dialect
+to Microsoft SQL-server (See more names in SQL::Abstract::Limit
+-documentation.
+
+ __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
-As your application evolves, it may be necessary to modify your schema to
-change functionality. Once the changes are made to your schema in DBIx::Class,
-export the modified schema as before, taking care not to overwrite the original:
+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)
- sqlt --from SQL::Translator::DBIx::Class
- --to MySQL
- --DBIx::Class "Anything.pm" > Schema2.mysql.sql
+The limit dialect can also be set at connect time by specifying a
+C<limit_dialect> key in the final hash as shown above.
-Next, use sqlt-diff to create an SQL script that will update the customer's
-database schema:
+=head2 Working with PostgreSQL array types
- sqlt-diff --to MySQL Schema1=MySQL Schema2=MySQL > SchemaUpdate.mysql.sql
+If your SQL::Abstract version (>= 1.50) supports it, you can assign to
+PostgreSQL array values by passing array references in the C<\%columns>
+(C<\%vals>) hashref of the L<DBIx::Class::ResultSet/create> and
+L<DBIx::Class::Row/update> family of methods:
-=head3 Deploy update to customers
+ $resultset->create({
+ numbers => [1, 2, 3]
+ });
-The schema update can be deployed to customers using the same method as before.
+ $row->update(
+ {
+ numbers => [1, 2, 3]
+ },
+ {
+ day => '2008-11-24'
+ }
+ );
+
+In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
+methods) you cannot directly use array references (since this is interpreted as
+a list of values to be C<OR>ed), but you can use the following syntax to force
+passing them as bind values:
+
+ $resultset->search(
+ {
+ numbers => \[ '= ?', [numbers => [1, 2, 3]] ]
+ }
+ );
+
+See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
+placeholders and bind values (subqueries)> for more explanation. Note that
+L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass
+the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in
+arrayrefs together with the column name, like this: C<< [column_name => value]
+>>.
+
+=head1 BOOTSTRAPPING/MIGRATING
+
+=head2 Easy migration from class-based to schema-based setup
+
+You want to start using the schema-based approach to L<DBIx::Class>
+(see L<SchemaIntro.pod>), but have an established class-based setup with lots
+of existing classes that you don't want to move by hand. Try this nifty script
+instead:
+
+ use MyDB;
+ use SQL::Translator;
+
+ my $schema = MyDB->schema_instance;
+
+ my $translator = SQL::Translator->new(
+ debug => $debug || 0,
+ trace => $trace || 0,
+ no_comments => $no_comments || 0,
+ show_warnings => $show_warnings || 0,
+ add_drop_table => $add_drop_table || 0,
+ validate => $validate || 0,
+ parser_args => {
+ 'DBIx::Schema' => $schema,
+ },
+ producer_args => {
+ '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;
-=head2 Setting limit dialect for SQL::Abstract::Limit
+You could use L<Module::Find> to search for all subclasses in the MyDB::*
+namespace, which is currently left as an exercise for the reader.
-In some cases, SQL::Abstract::Limit cannot determine the dialect of
-the remote SQL server by looking at the database handle. This is a
-common problem when using the DBD::JDBC, since the DBD-driver only
-know that in has a Java-driver available, not which JDBC driver the
-Java component has loaded. This specifically sets the limit_dialect
-to Microsoft SQL-server (See more names in SQL::Abstract::Limit
--documentation.
+=head1 OVERLOADING METHODS
- __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
+L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
+method calls, useful for things like default values and triggers. You have to
+use calls to C<next::method> to overload methods. More information on using
+L<Class::C3> with L<DBIx::Class> can be found in
+L<DBIx::Class::Manual::Component>.
-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)
+=head2 Setting default values for a row
-=head2 Setting quoting for the generated SQL.
+It's as simple as overriding the C<new> method. Note the use of
+C<next::method>.
-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:
+ sub new {
+ my ( $class, $attrs ) = @_;
- __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
- __PACKAGE__->storage->sql_maker->name_sep('.');
+ $attrs->{foo} = 'bar' unless defined $attrs->{foo};
-The first sets the quote characters. Either a pair of matching
-brackets, or a C<"> or C<'>:
-
- __PACKAGE__->storage->sql_maker->quote_char('"');
+ my $new = $class->next::method($attrs);
-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.
+ return $new;
+ }
-=head2 Overloading methods
+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.
-L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of
-method calls. You have to use calls to C<next::method> to overload methods.
-More information on using L<Class::C3> with L<DBIx::Class> can be found in
-L<DBIx::Class::Manual::Component>.
+People looking for ways to do "triggers" with DBIx::Class are probably
+just looking for this.
-=head3 Changing one field whenever another changes
+=head2 Changing one field whenever another changes
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
Note that the hard work is done by the call to C<next::method>, which
redispatches your call to store_column in the superclass(es).
-=head3 Automatically creating related objects
+=head2 Automatically creating related objects
You might have a class C<Artist> which has many C<CD>s. Further, if you
want to create a C<CD> object every time you insert an C<Artist> object.
where C<fill_from_artist> is a method you specify in C<CD> which sets
values in C<CD> based on the data in the C<Artist> object you pass in.
-=head2 Debugging DBIx::Class objects with Data::Dumper
+=head2 Wrapping/overloading a column accessor
+
+B<Problem:>
+
+Say you have a table "Camera" and want to associate a description
+with each camera. For most cameras, you'll be able to generate the description from
+the other columns. However, in a few special cases you may want to associate a
+custom description with a camera.
+
+B<Solution:>
+
+In your database schema, define a description field in the "Camera" table that
+can contain text and null values.
+
+In DBIC, we'll overload the column accessor to provide a sane default if no
+custom description is defined. The accessor will either return or generate the
+description, depending on whether the field is null or not.
+
+First, in your "Camera" schema class, define the description field as follows:
+
+ __PACKAGE__->add_columns(description => { accessor => '_description' });
+
+Next, we'll define the accessor-wrapper subroutine:
+
+ sub description {
+ my $self = shift;
+
+ # If there is an update to the column, we'll let the original accessor
+ # deal with it.
+ return $self->_description(@_) if @_;
+
+ # Fetch the column value.
+ my $description = $self->_description;
+
+ # If there's something in the description field, then just return that.
+ return $description if defined $description && length $descripton;
+
+ # Otherwise, generate a description.
+ return $self->generate_description;
+ }
+
+=head1 DEBUGGING AND PROFILING
+
+=head2 DBIx::Class objects with Data::Dumper
L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
be hard to find the pertinent data in all the data it can generate.
will automagically clean up your data before printing it. See
L<Data::Dumper/EXAMPLES> for more information.
-=head2 Retrieving a row object's Schema
-
-It is possible to get a Schema object from a row object like so:
-
- my $schema = $cd->result_source->schema;
- # use the schema as normal:
- 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 Profiling
-When you enable L<DBIx::Class::Storage::DBI>'s debugging it prints the SQL
+When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL
executed as well as notifications of query completion and transaction
begin/commit. If you'd like to profile the SQL you can subclass the
L<DBIx::Class::Storage::Statistics> class and write your own profiling
my $sql = shift();
my $params = @_;
- print "Executing $sql: ".join(', ', @params)."\n";
+ $self->print("Executing $sql: ".join(', ', @params)."\n");
$start = time();
}
my $sql = shift();
my @params = @_;
- printf("Execution took %0.4f seconds.\n", time() - $start);
+ my $elapsed = sprintf("%0.4f", time() - $start);
+ $self->print("Execution took $elapsed seconds.\n");
$start = undef;
}
You can then install that class as the debugging object:
- __PACKAGE__->storage()->debugobj(new My::Profiler());
- __PACKAGE__->storage()->debug(1);
+ __PACKAGE__->storage->debugobj(new My::Profiler());
+ __PACKAGE__->storage->debug(1);
A more complicated example might involve storing each execution of SQL in an
array:
You could then create average, high and low execution times for an SQL
statement and dig down to see if certain parameters cause aberrant behavior.
+You might want to check out L<DBIx::Class::QueryLog> as well.
-=head2 Getting the value of the primary key for the last database insert
-
-AKA getting last_insert_id
-
-If you are using PK::Auto, this is straightforward:
-
- my $foo = $rs->create(\%blah);
- # do more stuff
- my $id = $foo->id; # foo->my_primary_key_field will also work.
-
-If you are not using autoincrementing primary keys, this will probably
-not work, but then you already know the value of the last primary key anyway.
-
-=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
-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
-this.
-
-Overriding the C<inflate_result> method within the User proxy-class
-gives us the effect we want. This method is called by
-L<DBIx::Class::ResultSet> when inflating a result from storage. So we
-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 DB::Schema;
-
- use base qw/DBIx::Class::Schema/;
-
- __PACKAGE__->load_classes(qw/User/);
-
-
-B<Proxy-Class definitions>
-
- package DB::Schema::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 ;
- }
-
-
- package DB::Schema::User::Admin;
-
- use strict;
- use warnings;
- use base qw/DB::Schema::User/;
-
- sub hello
- {
- print "I am an admin.\n";
- return;
- }
-
- sub do_admin_stuff
- {
- print "I am doing admin stuff\n";
- return ;
- }
-
-B<Test File> test.pl
-
- use warnings;
- use strict;
- use DB::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 = DB::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 object creation for faster results
+=head1 STARTUP SPEED
-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. Luckily this is also fairly easy using
-C<inflate_result>:
-
- # Define a class which just returns the results as a hashref:
- package My::HashRefInflator;
-
- ## $me is the hashref of cols/data from the immediate resultsource
- ## $prefetch is a deep hashref of all the data from the prefetched
- ## related sources.
+L<DBIx::Class|DBIx::Class> programs can have a significant startup delay
+as the ORM loads all the relevant classes. This section examines
+techniques for reducing the startup delay.
- sub mk_hash {
- my ($me, $rest) = @_;
-
- return { %$me,
- map { ($_ => mk_hash(@{$rest->{$_}})) } keys %$rest
- };
- }
-
- sub inflate_result {
- my ($self, $source, $me, $prefetch) = @_;
- return mk_hash($me, $prefetch);
- }
+These tips are are listed in order of decreasing effectiveness - so the
+first tip, if applicable, should have the greatest effect on your
+application.
- # Change the object inflation to a hashref for just this resultset:
- $rs->result_class('My::HashRefInflator');
-
- my $datahashref = $rs->next;
- foreach my $col (keys %$datahashref) {
- if(!ref($datahashref->{$col})) {
- # It's a plain value
- }
- elsif(ref($datahashref->{$col} eq 'HASH')) {
- # It's a related value in a hashref
- }
- }
+=head2 Statically Define Your Schema
-=head2 Want to know if find_or_create found or created a row?
+If you are using
+L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the
+classes dynamically based on the database schema then there will be a
+significant startup delay.
-Just use C<find_or_new> instead, then check C<in_storage>:
+For production use a statically defined schema (which can be generated
+using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump
+the database schema once - see
+L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and
+L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more
+details on creating static schemas from a database).
- my $obj = $rs->find_or_new({ blah => 'blarg' });
- unless ($obj->in_storage) {
- $obj->insert;
- # do whatever else you wanted if it was a new row
- }
+=head2 Move Common Startup into a Base Class
-=head3 Wrapping/overloading a column accessor
+Typically L<DBIx::Class> result classes start off with
-Problem: Say you have a table "Camera" and want to associate a description
-with each camera. For most cameras, you'll be able to generate the description from
-the other columns. However, in a few special cases you may want to associate a
-custom description with a camera.
+ use base qw/DBIx::Class/;
+ __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
-Solution:
+If this preamble is moved into a common base class:-
-In your database schema, define a description field in the "Camera" table that
-can contain text and null values.
+ package MyDBICbase;
+
+ use base qw/DBIx::Class/;
+ __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
+ 1;
-In DBIC, we'll overload the column accessor to provide a sane default if no
-custom description is defined. The accessor will either return or generate the
-description, depending on whether the field is null or not.
+and each result class then uses this as a base:-
-First, in your "Camera" schema class, define the description field as follows:
+ use base qw/MyDBICbase/;
- __PACKAGE__->add_columns(description => { accessor => '_description' });
+then the load_components is only performed once, which can result in a
+considerable startup speedup for schemas with many classes.
-Next, we'll define the accessor-wrapper subroutine:
+=head2 Explicitly List Schema Result Classes
- sub description {
- my $self = shift;
+The schema class will normally contain
- # If there is an update to the column, we'll let the original accessor
- # deal with it.
- return $self->_description(@_) if @_;
+ __PACKAGE__->load_classes();
- # Fetch the column value.
- my $description = $self->_description;
+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:-
- # If there's something in the description field, then just return that.
- return $description if defined $description && length $descripton;
+ __PACKAGE__->load_classes(qw/ CD Artist Track /);
- # Otherwise, generate a description.
- return $self->generate_description;
- }
+If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces>
+syntax to load the appropriate classes there is not a direct alternative
+avoiding L<Module::Find|Module::Find>.
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff