Merge pull request #12137 from lann/fix_association_first_last

Make CollectionAssociation first/last with integer fetch with query

Conflicts:
	activerecord/CHANGELOG.md

3 files changed, 11 insertions, 6 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index fd06dc4862..05fc079033 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   `CollectionAssociation#first`/`#last` (e.g. `has_many`) use a `LIMIT`ed
+    query to fetch results rather than loading the entire collection.
+
+    *Lann Martin*
+
 *   Make possible to run SQLite rake tasks without the `Rails` constant defined.
 
     *Damien Mathieu*
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index 8744a57355..e32c0b0377 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -528,15 +528,13 @@ module ActiveRecord
         #   * target already loaded
         #   * owner is new record
         #   * target contains new or changed record(s)
-        #   * the first arg is an integer (which indicates the number of records to be returned)
         def fetch_first_or_last_using_find?(args)
           if args.first.is_a?(Hash)
             true
           else
             !(loaded? ||
               owner.new_record? ||
-              target.any? { |record| record.new_record? || record.changed? } ||
-              args.first.kind_of?(Integer))
+              target.any? { |record| record.new_record? || record.changed? })
           end
         end
 
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 4c0fa88917..ebeead0dc2 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -1414,15 +1414,17 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_calling_first_or_last_with_integer_on_association_should_load_association
+  def test_calling_first_or_last_with_integer_on_association_should_not_load_association
     firm = companies(:first_firm)
+    firm.clients.create(:name => 'Foo')
+    assert !firm.clients.loaded?
 
-    assert_queries 1 do
+    assert_queries 2 do
       firm.clients.first(2)
       firm.clients.last(2)
     end
 
-    assert firm.clients.loaded?
+    assert !firm.clients.loaded?
   end
 
   def test_calling_many_should_count_instead_of_loading_association