Using subselect for `delete_all` with `limit` or `offset`

Arel doesn't support subselect generation for DELETE unlike UPDATE yet,
but we already have that generation in connection adapters. We can
simply use the subselect generated by that one.

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
*   Using subselect for `delete_all` with `limit` or `offset`.

    *Ryuta Kamizono*

*   Undefine attribute methods on descendants when resetting column
    information.

@@ -553,4 +557,5 @@

    *Kevin McPhillips*


Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activerecord/CHANGELOG.md) for previous changes.

activerecord/lib/active_record/relation.rb

@@ -10,7 +10,7 @@ class Relation
    SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering,
                            :reverse_order, :distinct, :create_with, :skip_query_cache]
    CLAUSE_METHODS = [:where, :having, :from]
    INVALID_METHODS_FOR_DELETE_ALL = [:limit, :distinct, :offset, :group, :having]
    INVALID_METHODS_FOR_DELETE_ALL = [:distinct, :group, :having]

    VALUE_METHODS = MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS + CLAUSE_METHODS

@@ -365,8 +365,8 @@ def destroy_all
    #
    # If an invalid method is supplied, #delete_all raises an ActiveRecordError:
    #
    #   Post.limit(100).delete_all
    #   # => ActiveRecord::ActiveRecordError: delete_all doesn't support limit
    #   Post.distinct.delete_all
    #   # => ActiveRecord::ActiveRecordError: delete_all doesn't support distinct
    def delete_all
      invalid_methods = INVALID_METHODS_FOR_DELETE_ALL.select do |method|
        value = get_value(method)
@@ -384,7 +384,7 @@ def delete_all
      stmt = Arel::DeleteManager.new
      stmt.from(table)

      if has_join_values?
      if has_join_values? || has_limit_or_offset?
        @klass.connection.join_to_delete(stmt, arel, arel_attribute(primary_key))
      else
        stmt.wheres = arel.constraints

activerecord/test/cases/persistence_test.rb

@@ -76,6 +76,26 @@ def test_update_all_with_order_and_limit_and_offset_updates_subset_only
      assert_equal "bulk update!", posts(:thinking).body
      assert_not_equal "bulk update!", posts(:welcome).body
    end

    def test_delete_all_with_order_and_limit_deletes_subset_only
      author = authors(:david)
      limited_posts = Post.where(author: author).order(:id).limit(1)
      assert_equal 1, limited_posts.size
      assert_equal 2, limited_posts.limit(2).size
      assert_equal 1, limited_posts.delete_all
      assert_raise(ActiveRecord::RecordNotFound) { posts(:welcome) }
      assert posts(:thinking)
    end

    def test_delete_all_with_order_and_limit_and_offset_deletes_subset_only
      author = authors(:david)
      limited_posts = Post.where(author: author).order(:id).limit(1).offset(1)
      assert_equal 1, limited_posts.size
      assert_equal 2, limited_posts.limit(2).size
      assert_equal 1, limited_posts.delete_all
      assert_raise(ActiveRecord::RecordNotFound) { posts(:thinking) }
      assert posts(:welcome)
    end
  end

  def test_update_many

activerecord/test/cases/relations_test.rb

@@ -896,11 +896,9 @@ def test_delete_all_loaded
  end

  def test_delete_all_with_unpermitted_relation_raises_error
    assert_raises(ActiveRecord::ActiveRecordError) { Author.limit(10).delete_all }
    assert_raises(ActiveRecord::ActiveRecordError) { Author.distinct.delete_all }
    assert_raises(ActiveRecord::ActiveRecordError) { Author.group(:name).delete_all }
    assert_raises(ActiveRecord::ActiveRecordError) { Author.having("SUM(id) < 3").delete_all }
    assert_raises(ActiveRecord::ActiveRecordError) { Author.offset(10).delete_all }
  end

  def test_select_with_aggregates