From: Guillermo Roditi <groditi@cpan.org>
Date: Tue, 16 Dec 2008 21:27:06 +0000 (+0000)
Subject: Introduce 'any_null_means_no_value' option to eliminate wasteful queries. The option... 
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=c89815db08bb4cc35d69efefa8a27bf71ae13142;p=dbsrgits%2FDBIx-Class-Historic.git

Introduce 'any_null_means_no_value' option to eliminate wasteful queries. The option is off by default and must be explicitly turned on. Tests, + docs included
---

diff --git a/Changes b/Changes
index 8bd0118..4a114eb 100644
--- a/Changes
+++ b/Changes
@@ -3,6 +3,9 @@ Revision history for DBIx::Class
         - Classes submitted as result_class for a resultsource are now
           automatically loaded via ensure_loaded()
         - 'result_class' resultset attribute, identical to result_class()
+        - add 'any_null_means_no_value' option for relationship accessors of
+          type 'single'. This will prevent DBIC from querying the database
+          if one or more of the key columns IS NULL. Tests + docs (groditi)
 
 0.08099_05 2008-10-30 21:30:00 (UTC)
         - Rewritte of Storage::DBI::connect_info(), extended with an
diff --git a/lib/DBIx/Class/Relationship.pm b/lib/DBIx/Class/Relationship.pm
index b3f8507..ce8a96f 100644
--- a/lib/DBIx/Class/Relationship.pm
+++ b/lib/DBIx/Class/Relationship.pm
@@ -208,6 +208,13 @@ Cascading deletes are off by default on a C<belongs_to>
 relationship. To turn them on, pass C<< cascade_delete => 1 >>
 in the $attr hashref.
 
+By default, DBIC will attempt to query the related table for a row when the
+relationship accessor is called even if a foreign key member column IS NULL,
+which can be wasteful. To avoid this query from being performed, pass
+C<< any_null_means_no_value => 1 >> in the C<$attr> hashref. This only applies
+to accessors of type 'single' (when your accessor and foreign key have
+different names e.g. 'cd_id', and 'cd').
+
 NOTE: If you are used to L<Class::DBI> relationships, this is the equivalent
 of C<has_a>.
 
diff --git a/lib/DBIx/Class/Relationship/Accessor.pm b/lib/DBIx/Class/Relationship/Accessor.pm
index d9c24a4..f23ec4c 100644
--- a/lib/DBIx/Class/Relationship/Accessor.pm
+++ b/lib/DBIx/Class/Relationship/Accessor.pm
@@ -18,7 +18,7 @@ sub add_relationship_accessor {
   my ($class, $rel, $acc_type) = @_;
   my %meth;
   if ($acc_type eq 'single') {
-    my $rel_cond = $class->relationship_info($rel)->{cond};
+    my $rel_info = $class->relationship_info($rel);
     $meth{$rel} = sub {
       my $self = shift;
       if (@_) {
@@ -28,9 +28,12 @@ sub add_relationship_accessor {
         return $self->{_relationship_data}{$rel};
       } else {
         my $cond = $self->result_source->resolve_condition(
-          $rel_cond, $rel, $self
+          $rel_info->{cond}, $rel, $self
         );
-        return if grep { not defined } values %$cond;
+        if( exists $rel_info->{attrs}->{any_null_means_no_value}
+              && $rel_info->{attrs}->{any_null_means_no_value} ){
+          return if grep { not defined } values %$cond;
+        }
         my $val = $self->find_related($rel, {}, {});
         return unless $val;
         return $self->{_relationship_data}{$rel} = $val;
diff --git a/t/66relationship.t b/t/66relationship.t
index 3a96107..bfe7781 100644
--- a/t/66relationship.t
+++ b/t/66relationship.t
@@ -8,7 +8,7 @@ use DBICTest;
 
 my $schema = DBICTest->init_schema();
 
-plan tests => 72;
+plan tests => 73;
 
 # has_a test
 my $cd = $schema->resultset("CD")->find(4);
@@ -41,7 +41,18 @@ if ($INC{'DBICTest/HelperRels.pm'}) {
   } );
 }
 
-is( ($artist->search_related('cds'))[3]->title, 'Big Flop', 'create_related ok' );
+my $big_flop_cd = ($artist->search_related('cds'))[3];
+is( $big_flop_cd->title, 'Big Flop', 'create_related ok' );
+
+{ # make sure we are not making pointless select queries when a FK IS NULL
+  my $queries = 0;
+  $schema->storage->debugcb(sub { $queries++; });
+  $schema->storage->debug(1);
+  $big_flop_cd->genre; #should not trigger a select query
+  is($queries, 0, 'No Select made for belongs_to if key IS NULL');
+  $schema->storage->debug(0);
+  $schema->storage->debugcb(undef);
+}
 
 my( $rs_from_list ) = $artist->search_related_rs('cds');
 is( ref($rs_from_list), 'DBIx::Class::ResultSet', 'search_related_rs in list context returns rs' );
diff --git a/t/lib/DBICTest/Schema/CD.pm b/t/lib/DBICTest/Schema/CD.pm
index 6175be4..0c79e60 100644
--- a/t/lib/DBICTest/Schema/CD.pm
+++ b/t/lib/DBICTest/Schema/CD.pm
@@ -67,7 +67,7 @@ __PACKAGE__->belongs_to('genre', 'DBICTest::Schema::Genre',
         join_type => 'left',
         on_delete => 'SET NULL',
         on_update => 'CASCADE',
-
+        any_null_means_no_value => 1,
     },
 );