This results in something like the following C<WHERE> clause:
- WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
+ WHERE artist LIKE ? AND title LIKE ?
+
+And the following bind values for the placeholders: C<'%Lamb%'>, C<'%Fear of
+Fours%'>.
Other queries might require slightly more complex logic:
package My::Schema::Result::UserFriendsComplex;
use strict;
use warnings;
- use base qw/DBIx::Class/;
+ use base qw/DBIx::Class::Core/;
- __PACKAGE__->load_components('Core');
__PACKAGE__->table_class('DBIx::Class::ResultSource::View');
# ->table, ->add_columns, etc.
);
... 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>,
+that you cannot modify the rows it contains, e.g. cannot call L</update>,
L</delete>, ... on it).
Note that you cannot have bind parameters unless is_virtual is set to true.
# SELECT name name, LENGTH( name )
# FROM artist
-Note that the C<as> attribute B<has absolutely nothing to do> with the sql
+Note that the C<as> attribute B<has absolutely nothing to do> with the SQL
syntax C< SELECT foo AS bar > (see the documentation in
L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the
generated SQL via the C<-as> field attribute as follows:
# Or use DBIx::Class::AccessorGroup:
__PACKAGE__->mk_group_accessors('column' => 'name_length');
+See also L</Using SQL functions on the left hand side of a comparison>.
+
=head2 SELECT DISTINCT with multiple columns
my $rs = $schema->resultset('Artist')->search(
are in any way unsure about the use of the attributes above (C< join
>, C< select >, C< as > and C< group_by >).
-=head2 Subqueries (EXPERIMENTAL)
+=head2 Subqueries
You can write subqueries relatively easily in DBIC.
artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
});
-The usual operators ( =, !=, IN, NOT IN, etc) are supported.
+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,
+ artist_id => $inside_rs->get_column('id')->as_query, # does NOT work
});
=head3 Support
WHERE artist_id = me.artist_id
)
-=head3 EXPERIMENTAL
-
-Please note that subqueries are considered an experimental feature.
-
=head2 Predefined searches
You can write your own L<DBIx::Class::ResultSet> class by inheriting from it
1;
-To use your resultset, first tell DBIx::Class to create an instance of it
-for you, in your My::DBIC::Schema::CD class:
+If you're using L<DBIx::Class::Schema/load_namespaces>, simply place the file
+into the C<ResultSet> directory next to your C<Result> directory, and it will
+be automatically loaded.
+
+If however you are still using L<DBIx::Class::Schema/load_classes>, first tell
+DBIx::Class to create an instance of the ResultSet class for you, in your
+My::DBIC::Schema::CD class:
# class definition as normal
- __PACKAGE__->load_components(qw/ Core /);
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('cd');
# tell DBIC to use the custom ResultSet class
=head2 Using SQL functions on the left hand side of a comparison
-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,
+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. (Unless your RDBMS
+supports indexes on expressions - including return values of functions - and
+you create an index on the return value of the function in question.) However,
it can be accomplished with C<DBIx::Class> when necessary.
If you do not have quoting on, simply include the function in your search
$rs->search({ 'YEAR(date_of_birth)' => 1979 });
-With quoting on, or for a more portable solution, use the C<where>
-attribute:
+With quoting on, or for a more portable solution, use literal SQL values with
+placeholders:
- $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' });
+ $rs->search(\[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ]);
-=begin hidden
+ # Equivalent SQL:
+ # SELECT * FROM employee WHERE YEAR(date_of_birth) = ?
-(When the bind args ordering bug is fixed, this technique will be better
-and can replace the one above.)
+ $rs->search({
+ name => 'Bob',
+ -nest => \[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ],
+ });
-With quoting on, or for a more portable solution, use the C<where> and
-C<bind> attributes:
+ # Equivalent SQL:
+ # SELECT * FROM employee WHERE name = ? AND YEAR(date_of_birth) = ?
- $rs->search({}, {
- where => \'YEAR(date_of_birth) = ?',
- bind => [ 1979 ]
- });
+Note: the C<plain_value> string in the C<< [ plain_value => 1979 ] >> part
+should be either the same as the name of the column (do this if the type of the
+return value of the function is the same as the type of the column) or
+otherwise it's essentially a dummy string currently (use C<plain_value> as a
+habit). It is used by L<DBIx::Class> to handle special column types.
-=end hidden
+See also L<SQL::Abstract/Literal SQL with placeholders and bind values
+(subqueries)>.
=head1 JOINS AND PREFETCHING
package My::App::Schema;
- use base DBIx::Class::Schema;
+ use base 'DBIx::Class::Schema';
# load subclassed classes from My::App::Schema::Result/ResultSet
__PACKAGE__->load_namespaces;
use strict;
use warnings;
- use base My::Shared::Model::Result::Baz;
+ use base 'My::Shared::Model::Result::Baz';
# WARNING: Make sure you call table() again in your subclass,
# otherwise DBIx::Class::ResultSourceProxy::Table will not be called
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
+separate 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.
use strict;
use warnings;
- use base qw/DBIx::Class/;
+ use base qw/DBIx::Class::Core/;
### Define 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
### The statement below will print
print "I can do admin stuff\n" if $admin->can('do_admin_stuff');
+Alternatively you can use L<DBIx::Class::DynamicSubclass> that implements
+exactly the above functionality.
+
=head2 Skip row object creation for faster results
DBIx::Class is not built for speed, it's built for convenience and
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'} );
+ __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => { -desc => 'page_number'} } );
=head2 Filtering a relationship result set
This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
package My::User;
- use base 'DBIx::Class';
- __PACKAGE__->load_components('Core');
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('user');
__PACKAGE__->add_columns(qw/id name/);
__PACKAGE__->set_primary_key('id');
__PACKAGE__->many_to_many('addresses' => 'user_address', 'address');
package My::UserAddress;
- use base 'DBIx::Class';
- __PACKAGE__->load_components('Core');
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('user_address');
__PACKAGE__->add_columns(qw/user address/);
__PACKAGE__->set_primary_key(qw/user address/);
__PACKAGE__->belongs_to('address' => 'My::Address');
package My::Address;
- use base 'DBIx::Class';
- __PACKAGE__->load_components('Core');
+ use base 'DBIx::Class::Core';
__PACKAGE__->table('address');
__PACKAGE__->add_columns(qw/id street town area_code country/);
__PACKAGE__->set_primary_key('id');
$rs = $user->addresses(); # get all addresses for a user
$rs = $address->users(); # get all users for an address
+ my $address = $user->add_to_addresses( # returns a My::Address instance,
+ # NOT a My::UserAddress instance!
+ {
+ country => 'United Kingdom',
+ area_code => 'XYZ',
+ town => 'London',
+ street => 'Sesame',
+ }
+ );
+
=head2 Relationships across DB schemas
Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema>
declaration, like so...
package MyDatabase::Main::Artist;
- use base qw/DBIx::Class/;
- __PACKAGE__->load_components(qw/PK::Auto Core/);
+ use base qw/DBIx::Class::Core/;
__PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause
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.
+transaction to fail.
+
+=head2 Nested transactions and auto-savepoints
+
+If savepoints are supported by your RDBMS, it is possible to achieve true
+nested transactions with minimal effort. To enable auto-savepoints via nested
+transactions, supply the C<< auto_savepoint = 1 >> connection attribute.
+
+Here is an example of true nested transactions. In the example, we start a big
+task which will create several rows. Generation of data for each row is a
+fragile operation and might fail. If we fail creating something, depending on
+the type of failure, we want to abort the whole task, or only skip the failed
+row.
+
+ my $schema = MySchema->connect("dbi:Pg:dbname=my_db");
+
+ # Start a transaction. Every database change from here on will only be
+ # committed into the database if the eval block succeeds.
+ eval {
+ $schema->txn_do(sub {
+ # SQL: BEGIN WORK;
+
+ my $job = $schema->resultset('Job')->create({ name=> 'big job' });
+ # SQL: INSERT INTO job ( name) VALUES ( 'big job' );
+
+ for (1..10) {
+
+ # Start a nested transaction, which in fact sets a savepoint.
+ eval {
+ $schema->txn_do(sub {
+ # SQL: SAVEPOINT savepoint_0;
+
+ my $thing = $schema->resultset('Thing')->create({ job=>$job->id });
+ # SQL: INSERT INTO thing ( job) VALUES ( 1 );
+
+ if (rand > 0.8) {
+ # This will generate an error, thus setting $@
+
+ $thing->update({force_fail=>'foo'});
+ # SQL: UPDATE thing SET force_fail = 'foo'
+ # WHERE ( id = 42 );
+ }
+ });
+ };
+ if ($@) {
+ # SQL: ROLLBACK TO SAVEPOINT savepoint_0;
+
+ # There was an error while creating a $thing. Depending on the error
+ # we want to abort the whole transaction, or only rollback the
+ # changes related to the creation of this $thing
+
+ # Abort the whole job
+ if ($@ =~ /horrible_problem/) {
+ print "something horrible happend, aborting job!";
+ die $@; # rethrow error
+ }
+
+ # Ignore this $thing, report the error, and continue with the
+ # next $thing
+ print "Cannot create thing: $@";
+ }
+ # There was no error, so save all changes since the last
+ # savepoint.
+
+ # SQL: RELEASE SAVEPOINT savepoint_0;
+ }
+ });
+ };
+ if ($@) {
+ # There was an error while handling the $job. Rollback all changes
+ # since the transaction started, including the already committed
+ # ('released') savepoints. There will be neither a new $job nor any
+ # $thing entry in the database.
+
+ # SQL: ROLLBACK;
+
+ print "ERROR: $@\n";
+ }
+ else {
+ # There was no error while handling the $job. Commit all changes.
+ # Only now other connections can see the newly created $job and
+ # @things.
+
+ # SQL: COMMIT;
+
+ print "Ok\n";
+ }
+
+In this example it might be hard to see where the rollbacks, releases and
+commits are happening, but it works just the same as for plain L<<txn_do>>: If
+the C<eval>-block around C<txn_do> fails, a rollback is issued. If the C<eval>
+succeeds, the transaction is committed (or the savepoint released).
+
+While you can get more fine-grained controll using C<svp_begin>, C<svp_release>
+and C<svp_rollback>, it is strongly recommended to use C<txn_do> with coderefs.
=head1 SQL
To create a new database using the schema:
my $schema = My::Schema->connect($dsn);
- $schema->deploy({ add_drop_tables => 1});
+ $schema->deploy({ add_drop_table => 1});
To import created .sql files using the mysql client:
package MyAppDB::Dual;
use strict;
use warnings;
- use base 'DBIx::Class';
- __PACKAGE__->load_components("Core");
+ use base 'DBIx::Class::Core';
__PACKAGE__->table("Dual");
__PACKAGE__->add_columns(
"dummy",
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
+and warn if the user tries to run a newer schema version than the
database thinks it has.
-Alternatively, you can send the conversion sql scripts to your
+Alternatively, you can send the conversion SQL scripts to your
customers as above.
-=head2 Setting quoting for the generated SQL.
+=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:
}
);
-In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of
+In conditions (e.g. 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:
Typically L<DBIx::Class> result classes start off with
- use base qw/DBIx::Class/;
- __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
+ use base qw/DBIx::Class::Core/;
+ __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
If this preamble is moved into a common base class:-
package MyDBICbase;
- use base qw/DBIx::Class/;
- __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/);
+ use base qw/DBIx::Class::Core/;
+ __PACKAGE__->load_components(qw/InflateColumn::DateTime/);
1;
and each result class then uses this as a base:-
projects / dbsrgits/DBIx-Class.git / blobdiff