#419

backend/app/models/nico_tag_relation.rb

@@ -7,21 +7,4 @@ class NicoTagRelation < ApplicationRecord
 
   validates :nico_tag_id, presence: true
   validates :tag_id, presence: true
-
-  validate :nico_tag_must_be_nico
-  validate :tag_mustnt_be_nico
-
-  private
-
-  def nico_tag_must_be_nico
-    if nico_tag && nico_tag.category != 'nico'
-      errors.add :nico_tag_id, 'タグのカテゴリがニコニコである必要があります．'
-    end
-  end
-
-  def tag_mustnt_be_nico
-    if tag && tag.category == 'nico'
-      errors.add :tag_id, '連携先タグのカテゴリはニコニコであってはなりません．'
-    end
-  end
 end

backend/app/models/post.rb

@@ -92,7 +92,7 @@ class Post < ApplicationRecord
            inverse_of: :parent_post
   has_many :children, through: :child_post_implications, source: :post
 
-  has_many :post_external_tags, dependent: :delete_all
+  has_many :post_external_tags, dependent: :destroy
   has_many :external_tags, through: :post_external_tags
 
   has_one_attached :thumbnail

backend/app/models/post_external_tag.rb

@@ -1,4 +1,4 @@
 class PostExternalTag < ApplicationRecord
   belongs_to :post
-  belongs_to :external_tag
+  belongs_to :external_tag, counter_cache: :post_count
 end

backend/app/models/tag.rb

@@ -30,7 +30,7 @@ class Tag < ApplicationRecord
 
   has_many :reversed_nico_tag_relations,
            class_name: 'NicoTagRelation',
-           foreign_key: :nico_tag_id,
+           foreign_key: :tag_id,
            dependent: :destroy
   has_many :linked_nico_tags, through: :reversed_nico_tag_relations, source: :nico_tag
 
@@ -71,8 +71,6 @@ class Tag < ApplicationRecord
   validate :tag_name_must_be_canonical
   validate :category_must_be_deerjikist_with_deerjikists
 
-  def self.nico_tags = ExternalTag.where(platform: :nico)
-
   CATEGORY_PREFIXES = {
       'general:'    => :general,
       'gen:'        => :general,