Fix `count(:all)` with eager loading and having an order other than the driving table

This is a regression caused by 6beb4de.

In PostgreSQL, ORDER BY expressions must appear in SELECT list when
using DISTINCT.

When using `count(:all)` with eager loading, Active Record enforces
DISTINCT to count the driving table records only. 6beb4de was caused the
regression because `count(:all)` with DISTINCT path no longer removes
ORDER BY.

We need to ignore ORDER BY when DISTINCT is enforced, otherwise not
always generated valid SQL for PostgreSQL.

Fixes #31783.

1 files changed, 7 insertions, 1 deletions

diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index e682da6fed..82b15e565b 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -21,7 +21,7 @@ require "models/comment"
 require "models/rating"
 
 class CalculationsTest < ActiveRecord::TestCase
-  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books
+  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books, :posts, :comments
 
   def test_should_sum_field
     assert_equal 318, Account.sum(:credit_limit)
@@ -236,6 +236,12 @@ class CalculationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_count_with_eager_loading_and_custom_order
+    posts = Post.includes(:comments).order("comments.id")
+    assert_queries(1) { assert_equal 11, posts.count }
+    assert_queries(1) { assert_equal 11, posts.count(:all) }
+  end
+
   def test_distinct_count_all_with_custom_select_and_order
     accounts = Account.distinct.select("credit_limit % 10").order(Arel.sql("credit_limit % 10"))
     assert_queries(1) { assert_equal 3, accounts.count(:all) }