我有两个模型。
专辑
class Album < ActiveRecord::Base
has_one :post, as: :post_module, dependent: :destroy
end
帖子（具有标题属性）
class Post < ActiveRecord::Base
belongs_to :post_module, polymorphic: true
end
这是我的模板
<% @albums.each do |album| %>
<tr>
<td>
<%= link_to album.post.title, edit_admin_album_path(album) %> <br/>
</td>
</tr>
<% end %>
我尝试使用:includes并:references避免 N + 1 查询。
def index
@albums = Album.includes(:post).references(:post).to_a
end
但似乎 N + 1 查询仍然存在。这有什么问题？
SQL (0.2ms) SELECT `albums`.`id` AS t0_r0, `albums`.`product_num` AS t0_r1, `albums`.`created_at` AS t0_r2, `albums`.`updated_at` AS t0_r3, `posts`.`id` AS t1_r0, `posts`.`title` AS t1_r1, `posts`.`date` AS t1_r2, `posts`.`post_module_id` AS t1_r3, `posts`.`post_module_type` AS t1_r4, `posts`.`created_at` AS t1_r5, `posts`.`updated_at` AS t1_r6 FROM `albums` LEFT OUTER JOIN `posts` ON `posts`.`post_module_id` = `albums`.`id` AND `posts`.`post_module_type` = 'Album'
Post Load (0.3ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`post_module_id` = 18 AND `posts`.`post_module_type` = 'Album' ORDER BY `posts`.`id` ASC LIMIT 1
Post Load (0.2ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`post_module_id` = 20 AND `posts`.`post_module_type` = 'Album' ORDER BY `posts`.`id` ASC LIMIT 1
Post Load (0.2ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`post_module_id` = 21 AND `posts`.`post_module_type` = 'Album' ORDER BY `posts`.`id` ASC LIMIT 1
Post Load (0.2ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`post_module_id` = 22 AND `posts`.`post_module_type` = 'Album' ORDER BY `posts`.`id` ASC LIMIT 1
Post Load (0.1ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`post_module_id` = 23 AND `posts`.`post_module_type` = 'Album' ORDER BY `posts`.`id` ASC LIMIT 1