From: Matt Phillips <mattp@cpan.org>
Date: Thu, 25 Apr 2013 17:56:36 +0000 (-0400)
Subject: Stop adding empty caches to resultsets chained off prefetched objects
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=bdb4d9404c947de09d19c6af830518b5c9801094;p=dbsrgits%2FDBIx-Class-Historic.git

Stop adding empty caches to resultsets chained off prefetched objects

Prior to ce55688, the related_rs cache loading mechanism only conditionally
loaded if the base rs cache was defined. After this was removed an empty
arrayref (meaning "no related results") could potentially be set as the cache.
This commit ensures the cache is only set when there are actual cache results.
---

diff --git a/lib/DBIx/Class/ResultSet.pm b/lib/DBIx/Class/ResultSet.pm
index c322f06..fe00753 100644
--- a/lib/DBIx/Class/ResultSet.pm
+++ b/lib/DBIx/Class/ResultSet.pm
@@ -3163,15 +3163,6 @@ sub related_resultset {
     #XXX - temp fix for result_class bug. There likely is a more elegant fix -groditi
     delete @{$attrs}{qw(result_class alias)};
 
-    my $related_cache;
-
-    if (my $cache = $self->get_cache) {
-      $related_cache = [ map
-        { @{$_->related_resultset($rel)->get_cache||[]} }
-        @$cache
-      ];
-    }
-
     my $rel_source = $rsrc->related_source($rel);
 
     my $new = do {
@@ -3192,7 +3183,16 @@ sub related_resultset {
                        where => $attrs->{where},
                    });
     };
-    $new->set_cache($related_cache) if $related_cache;
+
+    if (my $cache = $self->get_cache) {
+      my @related_cache = map
+        { @{$_->related_resultset($rel)->get_cache||[]} }
+        @$cache
+      ;
+
+      $new->set_cache(\@related_cache) if @related_cache;
+    }
+
     $new;
   };
 }
diff --git a/t/prefetch/via_search_related.t b/t/prefetch/via_search_related.t
index e95d960..588b125 100644
--- a/t/prefetch/via_search_related.t
+++ b/t/prefetch/via_search_related.t
@@ -69,6 +69,47 @@ lives_ok ( sub {
 
 }, 'search_related prefetch with condition referencing unqualified column of a joined table works');
 
+# make sure chains off prefetched results still work
+{
+  my $cd = $schema->resultset('CD')->search({}, { prefetch => 'cd_to_producer' })->find(1);
+
+  $queries = 0;
+  $schema->storage->debugcb ($debugcb);
+  $schema->storage->debug (1);
+
+  is( $cd->cd_to_producer->count, 3 ,'Count of prefetched m2m links via accessor' );
+  is( scalar $cd->cd_to_producer->all, 3, 'Amount of prefetched m2m link objects via accessor' );
+  is( $cd->search_related('cd_to_producer')->count, 3, 'Count of prefetched m2m links via search_related' );
+  is( scalar $cd->search_related('cd_to_producer')->all, 3, 'Amount of prefetched m2m links via search_related' );
+
+  is($queries, 0, 'No queries ran so far');
+
+  is( scalar $cd->cd_to_producer->search_related('producer')->all, 3,
+      'Amount of objects via search_related off prefetched linker' );
+  is( $cd->cd_to_producer->search_related('producer')->count, 3,
+      'Count via search_related off prefetched linker' );
+  is( scalar $cd->search_related('cd_to_producer')->search_related('producer')->all, 3,
+      'Amount of objects via chained search_related off prefetched linker' );
+  is( $cd->search_related('cd_to_producer')->search_related('producer')->count, 3,
+      'Count via chained search_related off prefetched linker' );
+  is( scalar $cd->producers->all, 3,
+      'Amount of objects via m2m accessor' );
+  is( $cd->producers->count, 3,
+      'Count via m2m accessor' );
+
+  $queries = 0;
+
+  is( $cd->cd_to_producer->count, 3 ,'Review count of prefetched m2m links via accessor' );
+  is( scalar $cd->cd_to_producer->all, 3, 'Review amount of prefetched m2m link objects via accessor' );
+  is( $cd->search_related('cd_to_producer')->count, 3, 'Review count of prefetched m2m links via search_related' );
+  is( scalar $cd->search_related('cd_to_producer')->all, 3, 'Rreview amount of prefetched m2m links via search_related' );
+
+  is($queries, 0, 'Still no queries on prefetched linker');
+  $schema->storage->debugcb (undef);
+  $schema->storage->debug ($orig_debug);
+}
+
+# tests with distinct => 1
 lives_ok (sub {
     my $rs = $schema->resultset("Artwork")->search(undef, {distinct => 1})
               ->search_related('artwork_to_artist')->search_related('artist',