* Documented using PostgreSQL arrays in Cookbook.

[dbsrgits/DBIx-Class.git] / lib / DBIx / Class / Manual / Cookbook.pod

diff --git a/lib/DBIx/Class/Manual/Cookbook.pod b/lib/DBIx/Class/Manual/Cookbook.pod
index 83a633d..f63f067 100644 (file)
--- a/lib/DBIx/Class/Manual/Cookbook.pod
+++ b/lib/DBIx/Class/Manual/Cookbook.pod
@@ -68,6 +68,41 @@ This results in the following C<WHERE> clause:
 For more information on generating complex queries, see
 L<SQL::Abstract/WHERE CLAUSES>.
 
+=head2 Retrieve one and only one row from a resultset
+
+Sometimes you need only the first "top" row of a resultset. While this can be
+easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal,
+as a full blown cursor for the resultset will be created and then immediately
+destroyed after fetching the first row object. 
+L<< $rs->single|DBIx::Class::ResultSet/single >> is
+designed specifically for this case - it will grab the first returned result
+without even instantiating a cursor. 
+
+Before replacing all your calls to C<first()> with C<single()> please observe the 
+following CAVEATS:
+
+=over
+
+=item *
+While single() takes a search condition just like search() does, it does
+_not_ accept search attributes. However one can always chain a single() to
+a search():
+
+  my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single;
+
+
+=item *
+Since single() is the engine behind find(), it is designed to fetch a
+single row per database query. Thus a warning will be issued when the
+underlying SELECT returns more than one row. Sometimes however this usage
+is valid: i.e. we have an arbitrary number of cd's but only one of them is
+at the top of the charts at any given time. If you know what you are doing,
+you can silence the warning by explicitly limiting the resultset size:
+
+  my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single;
+
+=back
+
 =head2 Arbitrary SQL through a custom ResultSource
 
 Sometimes you have to run arbitrary SQL because your query is too complex
@@ -733,7 +768,7 @@ B<Test File> test.pl
     ### The statement below will print 
     print "I can do admin stuff\n" if $admin->can('do_admin_stuff'); 
 
-=head2 Skip object creation for faster results
+=head2 Skip row object creation for faster results
 
 DBIx::Class is not built for speed, it's built for convenience and
 ease of use, but sometimes you just need to get the data, and skip the
@@ -746,7 +781,7 @@ To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>.
  $rs->result_class('DBIx::Class::ResultClass::HashRefInflator');
  
  my $hash_ref = $rs->find(1);
-  
+
 Wasn't that easy?
   
 =head2 Get raw data for blindingly fast results
@@ -870,6 +905,12 @@ as follows:
 
   __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
 
+=head2 Filtering a relationship result set
+
+If you want to get a filtered result set, you can just add add to $attr as follows:
+
+ __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } );
+
 =head2 Many-to-many relationships
 
 This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>:
@@ -1257,6 +1298,40 @@ that Microsoft doesn't deliver native client libraries for. (e.g. Linux)
 The limit dialect can also be set at connect time by specifying a 
 C<limit_dialect> key in the final hash as shown above.
 
+=head2 Working with PostgreSQL array types
+
+If your SQL::Abstract version (>= 1.50) supports it, you can assign to
+PostgreSQL array values by passing array references in the C<\%columns>
+(C<\%vals>) hashref of the L<DBIx::Class::ResultSet/create> and
+L<DBIx::Class::Row/update> family of methods:
+
+  $resultset->create({
+    numbers => [1, 2, 3]
+  });
+
+  $row->update(
+    {
+      numbers => [1, 2, 3]
+    },
+    {
+      day => '2008-11-24'
+    }
+  );
+
+In conditions (eg. 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:
+
+  $resultset->search(
+    {
+      numbers => \[ '= ?', [1, 2, 3] ]
+    }
+  );
+
+See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with
+placeholders and bind values (subqueries)> for more explanation.
+
 =head1 BOOTSTRAPPING/MIGRATING 
 
 =head2 Easy migration from class-based to schema-based setup