}
);
+ my $count = $rs->next->get_column('count');
+
=head3 SELECT COUNT(DISTINCT colname)
my $rs = $schema->resultset('Foo')->search(
},
);
- $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;
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>:
+
+ sub insert {
+ my ( $class, $args_ref ) = @_;
+ my $self = $class->next::method($args_ref);
+ $self->cds->new({})->fill_from_artist($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;
+
+ $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.
+
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff