Revert "Optimize <association>_ids for hm:t with belongs_to source". The optimisation has too many edge cases, such as when the reflection, source reflection, or through reflection has conditions, orders, etc. [#6153 state:resolved]

This reverts commit 373b053dc8b99dac1abc3879a17a2bf8c30302b5.

Conflicts:

	activerecord/lib/active_record/associations.rb

2 files changed, 3 insertions, 14 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index c0cd222244..e4dff69efe 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1512,16 +1512,9 @@ module ActiveRecord
             if send(reflection.name).loaded? || reflection.options[:finder_sql]
               send(reflection.name).map { |r| r.id }
             else
-              if reflection.through_reflection && reflection.source_reflection.belongs_to?
-                through = reflection.through_reflection
-                primary_key = reflection.source_reflection.primary_key_name
-                send(through.name).select("DISTINCT #{through.quoted_table_name}.#{primary_key}").map! { |r| r.send(primary_key) }
-              else
-                send(reflection.name).select("#{reflection.quoted_table_name}.#{reflection.klass.primary_key}").except(:includes).map! { |r| r.id }
-              end
+              send(reflection.name).select("#{reflection.quoted_table_name}.#{reflection.klass.primary_key}").except(:includes).map! { |r| r.id }
             end
           end
-
         end
 
         def collection_accessor_methods(reflection, association_proxy_class, writer = true)
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index ad67886202..a244d310c8 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -334,12 +334,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal 2, people(:michael).jobs.size
   end
 
-  def test_get_ids_for_belongs_to_source
-    assert_sql(/DISTINCT/) { assert_equal [posts(:welcome).id, posts(:authorless).id].sort, people(:michael).post_ids.sort }
-  end
-
-  def test_get_ids_for_has_many_source
-    assert_equal [comments(:eager_other_comment1).id], authors(:mary).comment_ids
+  def test_get_ids
+    assert_equal [posts(:welcome).id, posts(:authorless).id].sort, people(:michael).post_ids.sort
   end
 
   def test_get_ids_for_loaded_associations