Fix GROUP BY queries to apply LIMIT/OFFSET after aggregations

If `eager_loading` is true, `apply_join_dependency` force applies
LIMIT/OFFSET before JOINs by `limited_ids_for` to keep parent records
count. But for aggregation queries, LIMIT/OFFSET should be applied after
aggregations the same as SQL semantics.

And also, we could not replace SELECT list by `limited_ids_for` when a
query has a GROUP BY clause. It had never been worked since it will
causes generating invalid SQL for MySQL, PostgreSQL, and probably most
backends.

```
% ARCONN=postgresql be ruby -w -Itest test/cases/calculations_test.rb -n test_group_by_with_limit
Using postgresql
Run options: -n test_group_by_with_limit --seed 20925

# Running:

E

Error:
CalculationsTest#test_group_by_with_limit:
ActiveRecord::StatementInvalid: PG::GroupingError: ERROR:  column "posts.id" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: SELECT  DISTINCT "posts"."id", "posts"."type" AS alias_0 FRO...                         ^
: SELECT  DISTINCT "posts"."id", "posts"."type" AS alias_0 FROM "posts" LEFT OUTER JOIN "comments" ON "comments"."post_id" = "posts"."id" GROUP BY "posts"."type" ORDER BY "posts"."type" ASC LIMIT $1
```

Fixes #8103.
Closes #27249.

1 files changed, 18 insertions, 0 deletions

diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 080d2a54bc..6ceac59eec 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -705,6 +705,24 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal [], Topic.includes(:replies).order(:id).offset(5).pluck(:id)
   end
 
+  def test_group_by_with_limit
+    expected = { "Post" => 8, "SpecialPost" => 1 }
+    actual = Post.includes(:comments).group(:type).order(:type).limit(2).count("comments.id")
+    assert_equal expected, actual
+  end
+
+  def test_group_by_with_offset
+    expected = { "SpecialPost" => 1, "StiPost" => 2 }
+    actual = Post.includes(:comments).group(:type).order(:type).offset(1).count("comments.id")
+    assert_equal expected, actual
+  end
+
+  def test_group_by_with_limit_and_offset
+    expected = { "SpecialPost" => 1 }
+    actual = Post.includes(:comments).group(:type).order(:type).offset(1).limit(1).count("comments.id")
+    assert_equal expected, actual
+  end
+
   def test_pluck_not_auto_table_name_prefix_if_column_included
     Company.create!(name: "test", contracts: [Contract.new(developer_id: 7)])
     ids = Company.includes(:contracts).pluck(:developer_id)