From: Chris Kampmeier <chris@kampers.net>
Date: Mon, 16 Mar 2009 05:56:32 -0700
Subject: [PATCH] Add #many? implementations for Scope and AssociationCollection so they use a SQL COUNT, if possible, instead of always loading the collection

---
 .../associations/association_collection.rb         |    8 ++++
 activerecord/lib/active_record/named_scope.rb      |   10 +++++-
 .../associations/has_many_associations_test.rb     |   39 ++++++++++++++++++++
 activerecord/test/cases/named_scope_test.rb        |   34 +++++++++++++++++
 4 files changed, 90 insertions(+), 1 deletions(-)

diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index 3aef1b2..1cb3051 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -302,6 +302,14 @@ module ActiveRecord
         end
       end
 
+      def many?
+        if block_given?
+          method_missing(:many?) { |*block_args| yield(*block_args) }
+        else
+          size > 1
+        end
+      end
+
       def uniq(collection = self)
         seen = Set.new
         collection.inject([]) do |kept, record|
diff --git a/activerecord/lib/active_record/named_scope.rb b/activerecord/lib/active_record/named_scope.rb
index 1f3ef30..569b89a 100644
--- a/activerecord/lib/active_record/named_scope.rb
+++ b/activerecord/lib/active_record/named_scope.rb
@@ -107,7 +107,7 @@ module ActiveRecord
 
     class Scope
       attr_reader :proxy_scope, :proxy_options, :current_scoped_methods_when_defined
-      NON_DELEGATE_METHODS = %w(nil? send object_id class extend find size count sum average maximum minimum paginate first last empty? any? respond_to?).to_set
+      NON_DELEGATE_METHODS = %w(nil? send object_id class extend find size count sum average maximum minimum paginate first last empty? any? many? respond_to?).to_set
       [].methods.each do |m|
         unless m =~ /^__/ || NON_DELEGATE_METHODS.include?(m.to_s)
           delegate m, :to => :proxy_found
@@ -166,6 +166,14 @@ module ActiveRecord
         end
       end
 
+      def many?
+        if block_given?
+          proxy_found.many? { |*block_args| yield(*block_args) }
+        else
+          size > 1
+        end
+      end
+
       protected
       def proxy_found
         @found || load_found
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 30edf79..012ef10 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -1017,6 +1017,45 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert firm.clients.loaded?
   end
 
+  def test_calling_many_should_count_instead_of_loading_association
+    firm = companies(:first_firm)
+    assert_queries(1) do
+      firm.clients.many?  # use count query
+    end
+    assert !firm.clients.loaded?
+  end
+
+  def test_calling_many_on_loaded_association_should_not_use_query
+    firm = companies(:first_firm)
+    firm.clients.collect  # force load
+    assert_no_queries { assert firm.clients.many? }
+  end
+
+  def test_calling_many_should_defer_to_collection_if_using_a_block
+    firm = companies(:first_firm)
+    assert_queries(1) do
+      firm.clients.expects(:size).never
+      firm.clients.many? { true }
+    end
+    assert firm.clients.loaded?
+  end
+
+  def test_calling_many_should_return_false_if_none_or_one
+    firm = companies(:another_firm)
+    assert !firm.clients_like_ms.many?
+    assert_equal 0, firm.clients_like_ms.size
+
+    firm = companies(:first_firm)
+    assert !firm.limited_clients.many?
+    assert_equal 1, firm.limited_clients.size
+  end
+
+  def test_calling_many_should_return_true_if_more_than_one
+    firm = companies(:first_firm)
+    assert firm.clients.many?
+    assert_equal 2, firm.clients.size
+  end
+
   def test_joins_with_namespaced_model_should_use_correct_type
     old = ActiveRecord::Base.store_full_sti_class
     ActiveRecord::Base.store_full_sti_class = true
diff --git a/activerecord/test/cases/named_scope_test.rb b/activerecord/test/cases/named_scope_test.rb
index ae6a54a..c33bee5 100644
--- a/activerecord/test/cases/named_scope_test.rb
+++ b/activerecord/test/cases/named_scope_test.rb
@@ -234,6 +234,40 @@ class NamedScopeTest < ActiveRecord::TestCase
     assert_no_queries { assert topics.any? }
   end
 
+  def test_many_should_not_load_results
+    topics = Topic.base
+    assert_queries(2) do
+      topics.many?   # use count query
+      topics.collect # force load
+      topics.many?   # use loaded (no query)
+    end
+  end
+
+  def test_many_should_call_proxy_found_if_using_a_block
+    topics = Topic.base
+    assert_queries(1) do
+      topics.expects(:size).never
+      topics.many? { true }
+    end
+  end
+
+  def test_many_should_not_fire_query_if_named_scope_loaded
+    topics = Topic.base
+    topics.collect # force load
+    assert_no_queries { assert topics.many? }
+  end
+
+  def test_many_should_return_false_if_none_or_one
+    topics = Topic.base.scoped(:conditions => {:id => 0})
+    assert !topics.many?
+    topics = Topic.base.scoped(:conditions => {:id => 1})
+    assert !topics.many?
+  end
+
+  def test_many_should_return_true_if_more_than_one
+    assert Topic.base.many?
+  end
+
   def test_should_build_with_proxy_options
     topic = Topic.approved.build({})
     assert topic.approved
-- 
1.6.1.3