paged resultset, which will fetch only a small number of records at a time:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
page => 1, # page to return (defaults to 1)
rows => 10, # number of results per page
The C<page> attribute does not have to be specified in your search:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
rows => 10,
}
specify which ones you need:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
- cols => [qw/ name /]
+ columns => [qw/ name /]
}
);
to access the returned value:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
select => [ 'name', { LENGTH => 'name' } ],
as => [qw/ name name_length /],
=head3 SELECT DISTINCT with multiple columns
my $rs = $schema->resultset('Foo')->search(
- {},
+ undef,
{
select => [
{ distinct => [ $source->columns ] }
}
);
+ my $count = $rs->next->get_column('count');
+
=head3 SELECT COUNT(DISTINCT colname)
my $rs = $schema->resultset('Foo')->search(
- {},
+ undef,
{
select => [
{ count => { distinct => 'colname' } }
L<DBIx::Class> supports C<GROUP BY> as follows:
my $rs = $schema->resultset('Artist')->search(
- {},
+ undef,
{
join => [qw/ cds /],
select => [ 'name', { count => 'cds.cdid' } ],
# LEFT JOIN cd cds ON ( cds.artist = me.artistid )
# GROUP BY name
+=head3 Predefined searches
+
+You can write your own DBIx::Class::ResultSet class by inheriting from it
+and define often used searches as methods:
+
+ package My::DBIC::ResultSet::CD;
+ use strict;
+ use warnings;
+ use base 'DBIx::Class::ResultSet';
+
+ sub search_cds_ordered {
+ my ($self) = @_;
+
+ return $self->search(
+ {},
+ { order_by => 'name DESC' },
+ );
+ }
+
+ 1;
+
+To use your resultset, first tell DBIx::Class to create an instance of it
+for you, in your My::DBIC::Schema::CD class:
+
+ __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
+
+Then call your new method in your code:
+
+ my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+
+
+=head3 Predefined searches without writing a ResultSet class
+
+Alternatively you can automatically generate a DBIx::Class::ResultSet
+class by using the ResultSetManager component and tagging your method
+as ResultSet:
+
+ __PACKAGE__->load_components(qw/ ResultSetManager Core /);
+
+ sub search_cds_ordered : ResultSet {
+ my ($self) = @_;
+ return $self->search(
+ {},
+ { order_by => 'name DESC' },
+ );
+ }
+
+Then call your method in the same way from your code:
+
+ my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+
=head2 Using joins and prefetch
You can use the C<join> attribute to allow searching on, or sorting your
so no additional SQL statements are executed. You now have a much more
efficient query.
-Note that as of L<DBIx::Class> 0.04, C<prefetch> cannot be used with
-C<has_many> relationships. You will get an error along the lines of "No
-accessor for prefetched ..." if you try.
+Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
+C<has_many> relationships.
Also note that C<prefetch> should only be used when you know you will
definitely use data from a related table. Pre-fetching related tables when you
deep using the same syntax as a multi-step join:
my $rs = $schema->resultset('Tag')->search(
- {},
+ undef,
{
prefetch => {
cd => 'artist'
my $tag = $rs->first;
print $tag->cd->artist->name;
+=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' });
+
=head2 Transactions
As of version 0.04001, there is improved transaction support in
-L<DBIx::Class::Storage::DBI>. Here is an example of the recommended
-way to use it:
+L<DBIx::Class::Storage::DBI> and L<DBIx::Class::Schema>. Here is an
+example of the recommended way to use it:
- my $genus = Genus->find(12);
- eval {
- MyDB->txn_begin;
+ 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);
$genus->update;
- cromulate($genus); # Can have a nested transation
- MyDB->txn_commit;
+ $schema->txn_do($coderef2); # Can have a nested transaction
+ return $genus->species;
+ };
+
+ my $rs;
+ eval {
+ $rs = $schema->txn_do($coderef1);
};
- if ($@) {
- # Rollback might fail, too
- eval {
- MyDB->txn_rollback
- };
+
+ if ($@) { # Transaction failed
+ die "the sky is falling!" #
+ if ($@ =~ /Rollback failed/); # Rollback failed
+
+ deal_with_failed_transaction();
}
-Currently, a nested commit will do nothing and a nested rollback will
-die. The code at each level must be sure to call rollback in the case
-of an error, to ensure that the rollback will propagate to the top
-level and be issued. Support for savepoints and for true nested
+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.
$class->next::method($attrs);
}
+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.
+
=head2 Stringification
Employ the standard stringification technique by using the C<overload>
your main database class to make sure it disconnects cleanly:
$SIG{INT} = sub {
- __PACKAGE__->storage->dbh->disconnect;
+ __PACKAGE__->storage->disconnect;
};
=head2 Schema import/export
validate => $validate || 0,
parser_args => {
'DBIx::Schema' => $schema,
- }
+ },
producer_args => {
'prefix' => 'My::Schema',
- }
+ },
);
- $translator->parser('DBIx::Class');
- $translator->producer('DBIx::Class::File');
+ $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::*
-namespace, which is currently left as an excercise for the reader.
+namespace, which is currently left as an exercise for the reader.
=head2 Schema versioning
The following example shows simplistically how you might use DBIx::Class to
deploy versioned schemas to your customers. The basic process is as follows:
-1) Create a DBIx::Class schema
-2) Save the schema
-3) Deploy to customers
-4) Modify schema to change functionality
-5) Deploy update to customers
+=over 4
+
+=item 1.
+
+Create a DBIx::Class schema
+
+=item 2.
+
+Save the schema
+
+=item 3.
+
+Deploy to customers
+
+=item 4.
+
+Modify schema to change functionality
+
+=item 5.
+
+Deploy update to customers
+
+=back
=head3 Create a DBIx::Class schema
There are several ways you could deploy your schema. These are probably
beyond the scope of this recipe, but might include:
-1) Require customer to apply manually using their RDBMS.
-2) Package along with your app, making database dump/schema update/tests
+=over 4
+
+=item 1.
+
+Require customer to apply manually using their RDBMS.
+
+=item 2.
+
+Package along with your app, making database dump/schema update/tests
all part of your install.
+=back
+
=head3 Modify the schema to change functionality
As your application evolves, it may be necessary to modify your schema to
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 quotes for the generated SQL.
+
+If the database contains columnames with spaces and/or reserved words, the
+SQL-query needs to be quoted. This is done using:
+
+ __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] );
+ __PACKAGE__->storage->sql_maker->name_sep('.');
+
+The first sets the quotesymbols. If the quote i "symmetric" as " or '
+
+ __PACKAGE__->storage->sql_maker->quote_char('"');
+
+is enough. If the left quote differs form the right quote, the first
+notation should be used. name_sep needs to be set to allow the
+SQL generator to put the quotes the correct place.
+
+=head2 Overloading methods
+
+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>.
+
+=head3 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
+C<squared> be automagically set to the value of C<number> squared.
+You can accomplish this by overriding C<store_column>:
+
+ sub store_column {
+ my ( $self, $name, $value ) = @_;
+ if ($name eq 'number') {
+ $self->squared($value * $value);
+ }
+ $self->next::method($name, $value);
+ }
+
+Note that the hard work is done by the call to C<next::method>, which
+redispatches your call to store_column to the superclass(es).
+
+=head3 Automatically creating related objects
+
+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:
+
+ sub insert {
+ my ( $self, @args ) = @_;
+ $self->next::method(@args);
+ $self->cds->new({})->fill_from_artist($self)->insert;
+ return $self;
+ }
+
+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
+
+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.
+Specifically, if one naively tries to use it like so,
+
+ use Data::Dumper;
+
+ my $cd = $schema->resultset('CD')->find(1);
+ print Dumper($cd);
+
+several pages worth of data from the CD object's schema and result source will
+be dumped to the screen. Since usually one is only interested in a few column
+values of the object, this is not very helpful.
+
+Luckily, it is possible to modify the data before L<Data::Dumper> outputs
+it. Simply define a hook that L<Data::Dumper> will call on the object before
+dumping it. For example,
+
+ package My::DB::CD;
+
+ sub _dumper_hook {
+ $_[0] = bless {
+ %{ $_[0] },
+ result_source => undef,
+ }, ref($_[0]);
+ }
+
+ [...]
+
+ use Data::Dumper;
+
+ local $Data::Dumper::Freezer = '_dumper_hook';
+
+ my $cd = $schema->resultset('CD')->find(1);
+ print Dumper($cd);
+ # dumps $cd without its ResultSource
+
+If the structure of your schema is such that there is a common base class for
+all your table classes, simply put a method similar to C<_dumper_hook> in the
+base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
+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;
+ my $artist_rs = $schema->resultset('Artist');
+ # for example
+
+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
+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
+mechanism:
+
+ package My::Profiler;
+ use strict;
+
+ use base 'DBIx::Class::Storage::Statistics';
+
+ use Time::HiRes qw(time);
+
+ my $start;
+
+ sub query_start {
+ my $self = shift();
+ my $sql = shift();
+ my $params = @_;
+
+ print "Executing $sql: ".join(', ', @params)."\n";
+ $start = time();
+ }
+
+ sub query_end {
+ my $self = shift();
+ my $sql = shift();
+ my @params = @_;
+
+ printf("Execution took %0.4f seconds.\n", time() - $start);
+ $start = undef;
+ }
+
+ 1;
+
+You can then install that class as the debugging object:
+
+ __PACKAGE__->storage()->debugobj(new My::Profiler());
+ __PACKAGE__->storage()->debug(1);
+
+A more complicated example might involve storing each execution of SQL in an
+array:
+
+ sub query_end {
+ my $self = shift();
+ my $sql = shift();
+ my @params = @_;
+
+ my $elapsed = time() - $start;
+ push(@{ $calls{$sql} }, {
+ params => \@params,
+ elapsed => $elapsed
+ });
+ }
+
+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.
+
+=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_results()> 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. Running the test file below will confirm this works.
+
+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/PK::Auto 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');
+
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff