+Columns and relationships which are excluded from the updates hashref aren't
+touched at all.
+
+=head2 Treatment of belongs_to relations
+
+In case the relationship is included but undefined in the updates hashref,
+all columns forming the relationship will be set to null.
+If not all of them are nullable, DBIx::Class will throw an error.
+
+Updating the relationship:
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ owner => $user->id,
+ });
+
+Clearing the relationship (only works if cols are nullable!):
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ owner => undef,
+ });
+
+=head2 Treatment of might_have relationships
+
+In case the relationship is included but undefined in the updates hashref,
+all columns forming the relationship will be set to null.
+
+Updating the relationship:
+
+ my $user = $user_rs->recursive_update( {
+ id => 1,
+ address => {
+ street => "101 Main Street",
+ city => "Podunk",
+ state => "New York",
+ }
+ });
+
+Clearing the relationship:
+
+ my $user = $user_rs->recursive_update( {
+ id => 1,
+ address => undef,
+ });
+
+=head2 Treatment of has_many relations
+
+If a relationship key is included in the data structure with a value of undef
+or an empty array, all existing related rows will be deleted, or their foreign
+key columns will be set to null.
+
+The exact behaviour depends on the nullability of the foreign key columns and
+the value of the "if_not_submitted" parameter. The parameter defaults to
+undefined which neither nullifies nor deletes.
+
+When the array contains elements they are updated if they exist, created when
+not and deleted if not included.
+
+=head3 All foreign table columns are nullable
+
+In this case recursive_update defaults to nullifying the foreign columns.
+
+=head3 Not all foreign table columns are nullable
+
+In this case recursive_update deletes the foreign rows.
+
+Updating the relationship:
+
+ Passing ids:
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ tags => [1, 2],
+ });
+
+ Passing hashrefs:
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ tags => [
+ {
+ id => 1,
+ file => 'file0'
+ },
+ {
+ id => 2,
+ file => 'file1',
+ },
+ ],
+ });
+
+ Passing objects:
+
+ TODO
+
+ You can even mix them:
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ tags => [ '2', { id => '3' } ],
+ });
+
+Clearing the relationship:
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ tags => undef,
+ });
+
+ This is the same as passing an empty array:
+
+ my $dvd = $dvd_rs->recursive_update( {
+ id => 1,
+ tags => [],
+ });
+
+=head2 Treatment of many-to-many pseudo relations
projects / chaz / p5-DBIx-Class-ResultSet-RecursiveUpdate / blobdiff