DBIx::Class::Schema(3)

NAME
DBIx::Class::Schema - composable schemas

SYNOPSIS
  package Library::Schema;
  use base qw/DBIx::Class::Schema/;

  # load all Result classes in Library/Schema/Result/
  __PACKAGE__->load_namespaces();

  package Library::Schema::Result::CD;
  use base qw/DBIx::Class::Core/;

  __PACKAGE__->load_components(qw/InflateColumn::DateTime/); # for example
  __PACKAGE__->table('cd');

  # Elsewhere in your code:
  my $schema1 = Library::Schema->connect(
    $dsn,
    $user,
    $password,
    { AutoCommit => 1 },
  );

  my $schema2 = Library::Schema->connect($coderef_returning_dbh);

  # fetch objects using Library::Schema::Result::DVD
  my $resultset = $schema1->resultset('DVD')->search( ... );
  my @dvd_objects = $schema2->resultset('DVD')->search( ... );

DESCRIPTION
Creates database classes based on a schema. This is the recommended way to use DBIx::Class and allows you to use more than one concurrent connection with your classes.

NB: If you're used to Class::DBI it's worth reading the "SYNOPSIS" carefully, as DBIx::Class does things a little differently. Note in particular which module inherits off which.

SETUP METHODS

  load_namespaces

Arguments: %options?

  package MyApp::Schema;
  __PACKAGE__->load_namespaces();

  __PACKAGE__->load_namespaces(
     result_namespace => 'Res',
     resultset_namespace => 'RSet',
     default_resultset_class => '+MyApp::Othernamespace::RSet',
  );

With no arguments, this method uses Module::Find to load all of the Result and ResultSet classes under the namespace of the schema from which it is called. For example, "My::Schema" will by default find and load Result classes named "My::Schema::Result::*" and ResultSet classes named "My::Schema::ResultSet::*".

ResultSet classes are associated with Result class of the same name. For example, "My::Schema::Result::CD" will get the ResultSet class "My::Schema::ResultSet::CD" if it is present.

Both Result and ResultSet namespaces are configurable via the "result_namespace" and "resultset_namespace" options.

Another option, "default_resultset_class" specifies a custom default ResultSet class for Result classes with no corresponding ResultSet.

All of the namespace and classname options are by default relative to the schema classname. To specify a fully-qualified name, prefix it with a literal "+". For example, "+Other::NameSpace::Result".

Warnings

You will be warned if ResultSet classes are discovered for which there are no matching Result classes like this:

  load_namespaces found ResultSet class $classname with no corresponding Result class

If a Result class is found to already have a ResultSet class set using "resultset_class" to some other class, you will be warned like this:

  We found ResultSet class '$rs_class' for '$result', but it seems
  that you had already set '$result' to use '$rs_set' instead

Examples

  # load My::Schema::Result::CD, My::Schema::Result::Artist,
  #    My::Schema::ResultSet::CD, etc...
  My::Schema->load_namespaces;

  # Override everything to use ugly names.
  # In this example, if there is a My::Schema::Res::Foo, but no matching
  #   My::Schema::RSets::Foo, then Foo will have its
  #   resultset_class set to My::Schema::RSetBase
  My::Schema->load_namespaces(
    result_namespace => 'Res',
    resultset_namespace => 'RSets',
    default_resultset_class => 'RSetBase',
  );

  # Put things in other namespaces
  My::Schema->load_namespaces(
    result_namespace => '+Some::Place::Results',
    resultset_namespace => '+Another::Place::RSets',
  );

To search multiple namespaces for either Result or ResultSet classes, use an arrayref of namespaces for that option. In the case that the same result (or resultset) class exists in multiple namespaces, later entries in the list of namespaces will override earlier ones.

  My::Schema->load_namespaces(
    # My::Schema::Results_C::Foo takes precedence over My::Schema::Results_B::Foo :
    result_namespace => [ 'Results_A', 'Results_B', 'Results_C' ],
    resultset_namespace => [ '+Some::Place::RSets', 'RSets' ],
  );

  load_classes

Arguments: @classes?, { $namespace => [ @classes ] }+

"load_classes" is an alternative method to "load_namespaces", both of which serve similar purposes, each with different advantages and disadvantages. In the general case you should use "load_namespaces", unless you need to be able to specify that only specific classes are loaded at runtime.

With no arguments, this method uses Module::Find to find all classes under the schema's namespace. Otherwise, this method loads the classes you specify (using use), and registers them (using "register_class").

It is possible to comment out classes with a leading "#", but note that perl will think it's a mistake (trying to use a comment in a qw list), so you'll need to add "no warnings 'qw';" before your load_classes call.

If any classes found do not appear to be Result class files, you will get the following warning:

   Failed to load $comp_class. Can't find source_name method. Is
   $comp_class really a full DBIC result class? Fix it, move it elsewhere,
   or make your load_classes call more specific.

Example:

  My::Schema->load_classes(); # loads My::Schema::CD, My::Schema::Artist,
                              # etc. (anything under the My::Schema namespace)

  # loads My::Schema::CD, My::Schema::Artist, Other::Namespace::Producer but
  # not Other::Namespace::LinerNotes nor My::Schema::Track
  My::Schema->load_classes(qw/ CD Artist #Track /, {
    Other::Namespace => [qw/ Producer #LinerNotes /],
  });

  storage_type

Arguments: $storage_type|{$storage_type, \%args}
Return Value: $storage_type|{$storage_type, \%args}
Default value: DBIx::Class::Storage::DBI

Set the storage class that will be instantiated when "connect" is called. If the classname starts with "::", the prefix "DBIx::Class::Storage" is assumed by "connect".

You want to use this to set subclasses of DBIx::Class::Storage::DBI in cases where the appropriate subclass is not autodetected.

If your storage type requires instantiation arguments, those are defined as a second argument in the form of a hashref and the entire value needs to be wrapped into an arrayref or a hashref. We support both types of refs here in order to play nice with your Config::[class] or your choice. See DBIx::Class::Storage::DBI::Replicated for an example of this.

  exception_action

Arguments: $code_reference
Return Value: $code_reference
Default value: None

When "throw_exception" is invoked and "exception_action" is set to a code reference, this reference will be called instead of "throw" in DBIx::Class::Exception, with the exception message passed as the only argument.

Your custom throw code must rethrow the exception, as "throw_exception" is an integral part of DBIC's internal execution control flow.

Example:

   package My::Schema;
   use base qw/DBIx::Class::Schema/;
   use My::ExceptionClass;
   __PACKAGE__->exception_action(sub { My::ExceptionClass->throw(@_) });
   __PACKAGE__->load_classes;

   # or:
   my $schema_obj = My::Schema->connect( .... );
   $schema_obj->exception_action(sub { My::ExceptionClass->throw(@_) });

  stacktrace

Arguments: boolean

Whether "throw_exception" should include stack trace information. Defaults to false normally, but defaults to true if $ENV{DBIC_TRACE} is true.

  sqlt_deploy_hook

Arguments: $sqlt_schema

An optional sub which you can declare in your own Schema class that will get passed the SQL::Translator::Schema object when you deploy the schema via "create_ddl_dir" or "deploy".

For an example of what you can do with this, see "Adding Indexes And Functions To Your SQL" in DBIx::Class::Manual::Cookbook.

Note that sqlt_deploy_hook is called by "deployment_statements", which in turn is called before "deploy". Therefore the hook can be used only to manipulate the SQL::Translator::Schema object before it is turned into SQL fed to the database. If you want to execute post-deploy statements which can not be generated by SQL::Translator, the currently suggested method is to overload "deploy" and use dbh_do.

METHODS

  connect

Arguments: @connectinfo
Return Value: $new_schema

Creates and returns a new Schema object. The connection info set on it is used to create a new instance of the storage backend and set it on the Schema object.

See "connect_info" in DBIx::Class::Storage::DBI for DBI-specific syntax on the @connectinfo argument, or DBIx::Class::Storage in general.

Note that "connect_info" expects an arrayref of arguments, but "connect" does not. "connect" wraps its arguments in an arrayref before passing them to "connect_info".

Overloading

"connect" is a convenience method. It is equivalent to calling $schema->clone->connection(@connectinfo). To write your own overloaded version, overload "connection" instead.

  resultset

Arguments: $source_name
Return Value: $resultset

  my $rs = $schema->resultset('DVD');

Returns the DBIx::Class::ResultSet object for the registered source name.

  sources

Return Value: @source_names

  my @source_names = $schema->sources;

Lists names of all the sources registered on this Schema object.

  source

Arguments: $source_name
Return Value: $result_source

  my $source = $schema->source('Book');

Returns the DBIx::Class::ResultSource object for the registered source name.

  class

Arguments: $source_name
Return Value: $classname

  my $class = $schema->class('CD');

Retrieves the Result class name for the given source name.

  txn_do

Arguments: $coderef, @coderef_args?
Return Value: The return value of $coderef

Executes $coderef with (optional) arguments @coderef_args atomically, returning its result (if any). Equivalent to calling $schema->storage->txn_do. See "txn_do" in DBIx::Class::Storage for more information.

This interface is preferred over using the individual methods "txn_begin", "txn_commit", and "txn_rollback" below.

WARNING: If you are connected with "AutoCommit => 0" the transaction is considered nested, and you will still need to call "txn_commit" to write your changes when appropriate. You will also want to connect with "auto_savepoint => 1" to get partial rollback to work, if the storage driver for your database supports it.

Connecting with "AutoCommit => 1" is recommended.

  txn_scope_guard
Runs "txn_scope_guard" on the schema's storage. See "txn_scope_guard" in DBIx::Class::Storage.

  txn_begin
Begins a transaction (does nothing if AutoCommit is off). Equivalent to calling $schema->storage->txn_begin. See "txn_begin" in DBIx::Class::Storage for more information.

  txn_commit
Commits the current transaction. Equivalent to calling $schema->storage->txn_commit. See "txn_commit" in DBIx::Class::Storage for more information.

  txn_rollback
Rolls back the current transaction. Equivalent to calling $schema->storage->txn_rollback. See "txn_rollback" in DBIx::Class::Storage for more information.

  storage
  my $storage = $schema->storage;

Returns the DBIx::Class::Storage object for this Schema. Grab this if you want to turn on SQL statement debugging at runtime, or set the quote character. For the default storage, the documentation can be found in DBIx::Class::Storage::DBI.

  populate

Arguments: $source_name, [ \@column_list, \@row_values+ ] | [ \%col_data+ ]
Return Value: \@result_objects (scalar context) | @result_objects (list context)

A convenience shortcut to "populate" in DBIx::Class::ResultSet. Equivalent to:

 $schema->resultset($source_name)->populate([...]);

NOTE
    The context of this method call has an important effect on what is submitted to storage. In void context data is fed directly to fastpath insertion routines provided by the underlying storage (most often "execute_for_fetch" in DBI), bypassing the new and insert calls on the Result class, including any augmentation of these methods provided by components. For example if you are using something like DBIx::Class::UUIDColumns to create primary keys for you, you will find that your PKs are empty. In this case you will have to explicitly force scalar or list context in order to create those values.

  connection

Arguments: @args
Return Value: $new_schema

Similar to "connect" except sets the storage object and connection data in-place on the Schema class. You should probably be calling "connect" to get a proper Schema object instead.

Overloading

Overload "connection" to change the behaviour of "connect".

  compose_namespace

Arguments: $target_namespace, $additional_base_class?
Return Value: $new_schema

For each DBIx::Class::ResultSource in the schema, this method creates a class in the target namespace (e.g. $target_namespace::CD, $target_namespace::Artist) that inherits from the corresponding classes attached to the current schema.

It also attaches a corresponding DBIx::Class::ResultSource object to the new $schema object. If $additional_base_class is given, the new composed classes will inherit from first the corresponding class from the current schema then the base class.

For example, for a schema with My::Schema::CD and My::Schema::Artist classes,

  $schema->compose_namespace('My::DB', 'Base::Class');
  print join (', ', @My::DB::CD::ISA) . "\n";
  print join (', ', @My::DB::Artist::ISA) ."\n";

will produce the output

  My::Schema::CD, Base::Class
  My::Schema::Artist, Base::Class

  svp_begin
Creates a new savepoint (does nothing outside a transaction). Equivalent to calling $schema->storage->svp_begin. See "svp_begin" in DBIx::Class::Storage for more information.

  svp_release
Releases a savepoint (does nothing outside a transaction). Equivalent to calling $schema->storage->svp_release. See "svp_release" in DBIx::Class::Storage for more information.

  svp_rollback
Rollback to a savepoint (does nothing outside a transaction). Equivalent to calling $schema->storage->svp_rollback. See "svp_rollback" in DBIx::Class::Storage for more information.

  clone

Arguments: %attrs?
Return Value: $new_schema

Clones the schema and its associated result_source objects and returns the copy. The resulting copy will have the same attributes as the source schema, except for those attributes explicitly overridden by the provided %attrs.

  throw_exception

Arguments: $message

Throws an exception. Obeys the exemption rules of DBIx::Class::Carp to report errors from outer-user's perspective. See "exception_action" for details on overriding this method's behavior. If "stacktrace" is turned on, "throw_exception"'s default behavior will provide a detailed stack trace.

  deploy

Arguments: \%sqlt_args, $dir

Attempts to deploy the schema to the current storage using SQL::Translator.

See "METHODS" in SQL::Translator for a list of values for "\%sqlt_args". The most common value for this would be "{ add_drop_table => 1 }" to have the SQL produced include a "DROP TABLE" statement for each table created. For quoting purposes supply "quote_identifiers".

Additionally, the DBIx::Class parser accepts a "sources" parameter as a hash ref or an array ref, containing a list of source to deploy. If present, then only the sources listed will get deployed. Furthermore, you can use the "add_fk_index" parser parameter to prevent the parser from creating an index for each FK.

  deployment_statements

Arguments: See "deployment_statements" in DBIx::Class::Storage::DBI
Return Value: $listofstatements

A convenient shortcut to "$self->storage->deployment_statements($self, @args)". Returns the SQL statements used by "deploy" and "deploy" in DBIx::Class::Schema::Storage.

  create_ddl_dir

Arguments: See "create_ddl_dir" in DBIx::Class::Storage::DBI

A convenient shortcut to "$self->storage->create_ddl_dir($self, @args)".

Creates an SQL file based on the Schema, for each of the specified database types, in the given directory.

  ddl_filename

Arguments: $database-type, $version, $directory, $preversion
Return Value: $normalised_filename

  my $filename = $table->ddl_filename($type, $version, $dir, $preversion)

This method is called by "create_ddl_dir" to compose a file name out of the supplied directory, database type and version number. The default file name format is: "$dir$schema-$version-$type.sql".

You may override this method in your schema if you wish to use a different format.

 WARNING

 Prior to DBIx::Class version 0.08100 this method had a different signature:

    my $filename = $table->ddl_filename($type, $dir, $version, $preversion)

 In recent versions variables $dir and $version were reversed in order to
 bring the signature in line with other Schema/Storage methods. If you
 really need to maintain backward compatibility, you can do the following
 in any overriding methods:

    ($dir, $version) = ($version, $dir) if ($DBIx::Class::VERSION < 0.08100);

  thaw
Provided as the recommended way of thawing schema objects. You can call "Storable::thaw" directly if you wish, but the thawed objects will not have a reference to any schema, so are rather useless.

  freeze
This doesn't actually do anything more than call "nfreeze" in Storable, it is just provided here for symmetry.

  dclone

Arguments: $object
Return Value: dcloned $object

Recommended way of dcloning DBIx::Class::Row and DBIx::Class::ResultSet objects so their references to the schema object (which itself is not cloned) are properly maintained.

  schema_version
Returns the current schema class' $VERSION in a normalised way.

  register_class

Arguments: $source_name, $component_class

This method is called by "load_namespaces" and "load_classes" to install the found classes into your Schema. You should be using those instead of this one.

You will only need this method if you have your Result classes in files which are not named after the packages (or all in the same file). You may also need it to register classes at runtime.

Registers a class which isa DBIx::Class::ResultSourceProxy. Equivalent to calling:

  $schema->register_source($source_name, $component_class->result_source_instance);

  register_source

Arguments: $source_name, $result_source

This method is called by "register_class".

Registers the DBIx::Class::ResultSource in the schema with the given source name.

  unregister_source

Arguments: $source_name

Removes the DBIx::Class::ResultSource from the schema for the given source name.

  register_extra_source

Arguments: $source_name, $result_source

As "register_source" but should be used if the result class already has a source and you want to register an extra one.

  compose_connection (DEPRECATED)

Arguments: $target_namespace, @db_info
Return Value: $new_schema

DEPRECATED. You probably wanted compose_namespace.

Actually, you probably just wanted to call connect.

AUTHOR AND CONTRIBUTORS
See AUTHOR and CONTRIBUTORS in DBIx::Class

LICENSE
You may distribute this code under the same terms as Perl itself.