From: Rob Kinyon <rkinyon@cpan.org>
Date: Mon, 16 Feb 2009 21:27:49 +0000 (+0000)
Subject: Added a bit of explanation to resultsets to cut down on the repeated questions in... 
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=f57764b91d51a0c23ff0dd34b11a30689d456b95;p=dbsrgits%2FDBIx-Class-Historic.git

Added a bit of explanation to resultsets to cut down on the repeated questions in #dbix-class
---

diff --git a/lib/DBIx/Class/ResultSet.pm b/lib/DBIx/Class/ResultSet.pm
index 24b8981..1d0131a 100644
--- a/lib/DBIx/Class/ResultSet.pm
+++ b/lib/DBIx/Class/ResultSet.pm
@@ -52,6 +52,86 @@ In the examples below, the following table classes are used:
   __PACKAGE__->belongs_to(artist => 'MyApp::Schema::Artist');
   1;
 
+=head1 DISCUSSION
+
+When you create a resultset (usually as a result of calling search()), DBIx::Class
+B<doesn't> make a DB call. Not yet. A resultset is (in simplistic terms) a set of
+where conditions, join conditions, and other metadata that would be needed to execute
+a SELECT statement. This has several big implications:
+
+=over 4
+
+=item * You can chain resultsets
+
+=item * You can run multiple queries using the same resultset
+
+=back
+
+=head2 Chaining resultsets
+
+Let's say you've got a query that needs to be run to return some data to the user. But,
+you have an authorization system in place that prevents certain users from seeing certain
+information. So, you want to construct the query in one method, but add constraints to it
+in another.
+
+  sub get_data {
+    my $self = shift;
+    my $request = $self->get_request; # Get a request object somehow.
+    my $schema = $self->get_schema;   # Get the DBIC schema object somehow.
+
+    my $rs = $schema->resultset('some_data')->search({
+      foo => $request->param('foo'),
+      bar => $request->param('bar'),
+    });
+
+    $self->apply_security_policy( $rs );
+
+    return $rs->all;
+  }
+
+  sub apply_security_policy {
+    my $self = shift;
+    my ($rs) = @_;
+
+    return $rs->search({
+      hidden_data => 0,
+    });
+  }
+
+=head2 Multiple queries
+
+Since a resultset hasn't hit the database yet, you can do all sorts of things with it.
+
+  # Don't hit the DB yet.
+  my $rs = $schema->resultset('some_table')->search({
+    foo => 1,
+    bar => 2,
+  });
+
+  # Each of these hits the DB individually.
+  my $count = $rs->count;
+  my $max_baz = $rs->get_column('baz')->max;
+  my @records = $rs->all;
+
+And it's not just limited to SELECT statements.
+
+  $rs->delete;
+
+This is even cooler
+
+  $rs->create({ baz => 20 });
+
+That is equivalent to
+
+  $schema->resultset('some_table')->create({
+    foo => 1,
+    bar => 2,
+    baz => 20,
+  });
+
+Note that C<get_column()> returns a ResultSetColumn object. This will behave almost
+exactly like a resultset, except it has methods tuned for working with columns.
+
 =head1 OVERLOADING
 
 If a resultset is used in a numeric context it returns the L</count>.