=head3 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();
For more information on generating complex queries, see
L<SQL::Abstract/WHERE CLAUSES>.
+=head3 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_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>.
+
=head3 Using specific columns
When you only want specific columns from a table, you can use
);
# Equivalent SQL:
- # SELECT name name, LENGTH( name ) name_length
+ # SELECT name name, LENGTH( name )
# FROM artist
-If your alias exists as a column in your base class (i.e. it was added
-with C<add_columns>), you just access it as normal. Our C<Artist>
-class has a C<name> column, so we just use the C<name> accessor:
+Note that the C< as > attribute has absolutely nothing to with the sql
+syntax C< SELECT foo AS bar > (see the documentation in
+L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a
+column in your base class (i.e. it was added with C<add_columns>), you
+just access it as normal. Our C<Artist> class has a C<name> column, so
+we just use the C<name> accessor:
my $artist = $rs->first();
my $name = $artist->name();
select => [
{ distinct => [ $source->columns ] }
],
- as => [ $source->columns ]
+ as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-)
}
);
# LEFT JOIN cd cds ON ( cds.artist = me.artistid )
# 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
You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
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
join => [qw/ artist /],
order_by => [qw/ artist.name /]
}
- };
+ );
# Equivalent SQL:
# SELECT cd.* FROM cd
{},
{
select => [ { sum => 'Cost' } ],
- as => [ 'total_cost' ],
+ as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL
}
);
my $tc = $rs->first->get_column('total_cost');
=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
+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);
$attrs->{foo} = 'bar' unless defined $attrs->{foo};
- $class->next::method($attrs);
+ my $new = $class->next::method($attrs);
+
+ return $new;
}
For more information about C<next::method>, look in the L<Class::C3>
ways to write your own base classes to do this.
People looking for ways to do "triggers" with DBIx::Class are probably
-just looking for this.
+just looking for this.
=head2 Stringification
To make an object stringify itself as a single column, use something
like this (replace C<foo> with the column/method of your choice):
- use overload '""' => 'foo', fallback => 1;
+ use overload '""' => sub { shift->name}, fallback => 1;
For more complex stringification, you can use an anonymous subroutine:
=head2 Schema import/export
-This functionality requires you to have L<SQL::Translator> (also known as
-"SQL Fairy") installed.
+To create a DBIx::Class schema from an existing database, use
+L<DBIx::Class::Schema::Loader>'s C<make_schema_at>:
-To create a DBIx::Class schema from an existing database:
+ 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" ])'
- sqlt --from DBI
- --to DBIx::Class::File
- --prefix "MySchema" > MySchema.pm
+The following functionality requires you to have L<SQL::Translator>
+(also known as "SQL Fairy") installed.
-To create a MySQL database from an existing L<DBIx::Class> schema, convert the
-schema to MySQL's dialect of SQL:
+To create a set of database-specific .sql files for the above schema:
- sqlt --from SQL::Translator::Parser::DBIx::Class
- --to MySQL
- --DBIx::Class "MySchema.pm" > Schema1.sql
-
-And import using the mysql client:
+ 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);
+ $schema->deploy({ add_drop_tables => 1});
+
+To import created .sql files using the mysql client:
+
+ mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql
+
+To create C<ALTER TABLE> conversion scripts to update a database to a
+newer version of your schema at a later point, first set a new
+$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.
- mysql -h "host" -D "database" -u "user" -p < Schema1.sql
=head2 Easy migration from class-based to schema-based setup
=head3 Save the schema
-Use C<sqlt> to transform your schema into an SQL script suitable for your
-customer's database. E.g. for MySQL:
-
- 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
+Call L<DBIx::Class::Schema/create_ddl_dir> as above under L<Schema
+import/export>.
=head3 Deploy to customers
=head3 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 as before, taking care not to overwrite the original:
-
- sqlt --from SQL::Translator::DBIx::Class
- --to MySQL
- --DBIx::Class "Anything.pm" > Schema2.mysql.sql
-
-Next, use sqlt-diff to create an SQL script that will update the customer's
-database schema:
-
- sqlt-diff --to MySQL Schema1=MySQL Schema2=MySQL > SchemaUpdate.mysql.sql
+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<Schema import/export>.
=head3 Deploy update to customers
-The schema update can be deployed to customers using the same method as before.
+Add the L<DBIx::Class::Schema::Versioned> schema component to your
+Schema class. This will add a new table to your database called
+C<SchemaVersions> 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 limit dialect for SQL::Abstract::Limit
=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> 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>.
=head3 Changing one field whenever another changes
=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
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.
+fancy objects.
+
+To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
+
+ my $rs = $schema->resultset('CD');
+
+ $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
+
+ my $hash_ref = $rs->find(1);
+
+Wasn't that easy?
+
+=head2 Get raw data for blindingly fast results
- sub mk_hash {
- my ($me, $rest) = @_;
+If the C<inflate_result> solution above is not fast enough for you, you
+can use a DBIx::Class to return values exactly as they come out of the
+data base with none of the convenience methods wrapped round them.
- return { %$me,
- map { ($_ => mk_hash(@{$rest->{$_}})) } keys %$rest
- };
- }
+This is used like so:-
- sub inflate_result {
- my ($self, $source, $me, $prefetch) = @_;
- return mk_hash($me, $prefetch);
+ my $cursor = $rs->cursor
+ while (my @vals = $cursor->next) {
+ # use $val[0..n] here
}
- # 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
- }
- }
+You will need to map the array offsets to particular columns (you can
+use the I<select> attribute of C<search()> to force ordering).
=head2 Want to know if find_or_create found or created a row?
projects / dbsrgits/DBIx-Class.git / blobdiff