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
deep using the same syntax as a multi-step join:
my $rs = $schema->resultset('Tag')->search(
- {},
+ undef,
{
prefetch => {
cd => 'artist'
=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 $coderef1 = sub {
+ my ($schema, $genus, $code) = @_;
$genus->add_to_species({ name => 'troglodyte' });
$genus->wings(2);
$genus->update;
- cromulate($genus); # Can have a nested transation
- MyDB->txn_commit;
+ $schema->txn_do($code, $genus); # Can have a nested transaction
+ return $genus->species;
+ };
+
+ my $coderef2 = sub {
+ my ($genus) = @_;
+ $genus->extinct(1);
+ $genus->update;
};
- if ($@) {
- # Rollback might fail, too
- eval {
- MyDB->txn_rollback
- };
+
+ my $rs;
+ eval {
+ $rs = $schema->txn_do($coderef1, $schema, $genus, $coderef2);
+ };
+
+ if ($@) { # 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');
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 schema update can be deployed to customers using the same method as before.
+=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 (Se more names
+in SQL::Abstract::Limit -documentation.
+
+ __PACKAGE__->storage->sql_maker->limit_dialect('mssql');
+
+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.
+
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff