Merge branch 'main' into feature/215

backend/app/controllers/nico_tags_controller.rb

@@ -1,9 +1,13 @@
 class NicoTagsController < ApplicationController
+  TAG_JSON = { only: [:id, :category, :post_count], methods: [:name, :has_wiki] }.freeze
+
   def index
     limit = (params[:limit] || 20).to_i
     cursor = params[:cursor].presence
 
-    q = Tag.nico_tags.includes(:linked_tags).order(updated_at: :desc)
+    q = Tag.nico_tags
+           .includes(:tag_name, linked_tags: :tag_name)
+           .order(updated_at: :desc)
     q = q.where('tags.updated_at < ?', Time.iso8601(cursor)) if cursor
 
     tags = q.limit(limit + 1)
@@ -15,7 +19,9 @@ class NicoTagsController < ApplicationController
     end
 
     render json: { tags: tags.map { |tag|
-      tag.as_json(include: :linked_tags)
+      tag.as_json(TAG_JSON).merge(linked_tags: tag.linked_tags.map { |lt|
+        lt.as_json(TAG_JSON)
+      })
     }, next_cursor: }
   end
 
@@ -30,12 +36,11 @@ class NicoTagsController < ApplicationController
 
     linked_tag_names = params[:tags].to_s.split(' ')
     linked_tags = Tag.normalise_tags(linked_tag_names, with_tagme: false)
-    return head :bad_request if linked_tags.filter { |t| t.category == 'nico' }.present?
+    return head :bad_request if linked_tags.any? { |t| t.category == 'nico' }
 
     tag.linked_tags = linked_tags
-    tag.updated_at = Time.now
     tag.save!
 
-    render json: tag.linked_tags, status: :ok
+    render json: tag.linked_tags.map { |t| t.as_json(TAG_JSON) }, status: :ok
   end
 end

backend/app/controllers/posts_controller.rb

@@ -1,7 +1,6 @@
 class PostsController < ApplicationController
   Event = Struct.new(:post, :tag, :user, :change_type, :timestamp, keyword_init: true)
 
-  # GET /posts
   def index
     page = (params[:page].presence || 1).to_i
     limit = (params[:limit].presence || 20).to_i
@@ -18,7 +17,7 @@ class PostsController < ApplicationController
         'posts.created_at)'
     q =
         filtered_posts
-        .preload(:tags)
+        .preload(tags: :tag_name)
         .with_attached_thumbnail
         .select("posts.*, #{ sort_sql } AS sort_ts")
         .order(Arel.sql("#{ sort_sql } DESC"))
@@ -36,7 +35,8 @@ class PostsController < ApplicationController
     end
 
     render json: { posts: posts.map { |post|
-      post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }).tap do |json|
+      post.as_json(include: { tags: { only: [:id, :category, :post_count],
+                                      methods: [:name] } }).tap do |json|
         json['thumbnail'] =
             if post.thumbnail.attached?
               rails_storage_proxy_url(post.thumbnail, only_path: false)
@@ -48,19 +48,19 @@ class PostsController < ApplicationController
   end
 
   def random
-    post = filtered_posts.order('RAND()').first
+    post = filtered_posts.preload(tags: :tag_name).order('RAND()').first
     return head :not_found unless post
 
     viewed = current_user&.viewed?(post) || false
 
     render json: (post
-                  .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
+                  .as_json(include: { tags: { only: [:id, :category, :post_count],
+                                              methods: [:name] } })
                   .merge(viewed:))
   end
 
-  # GET /posts/1
   def show
-    post = Post.includes(:tags).find(params[:id])
+    post = Post.includes(tags: :tag_name).find(params[:id])
     return head :not_found unless post
 
     viewed = current_user&.viewed?(post) || false
@@ -73,7 +73,6 @@ class PostsController < ApplicationController
     render json:
   end
 
-  # POST /posts
   def create
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.member?
@@ -96,7 +95,8 @@ class PostsController < ApplicationController
       tags = Tag.normalise_tags(tag_names)
       tags = Tag.expand_parent_tags(tags)
       sync_post_tags!(post, tags)
-      render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
+      render json: post.as_json(include: { tags: { only: [:id, :category, :post_count],
+                                                   methods: [:name] } }),
              status: :created
     else
       render json: { errors: post.errors.full_messages }, status: :unprocessable_entity
@@ -117,7 +117,6 @@ class PostsController < ApplicationController
     head :no_content
   end
 
-  # PATCH/PUT /posts/1
   def update
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.member?
@@ -153,13 +152,13 @@ class PostsController < ApplicationController
 
     pts = PostTag.with_discarded
     pts = pts.where(post_id: id) if id.present?
-    pts = pts.includes(:post, :tag, :created_user, :deleted_user)
+    pts = pts.includes(:post, { tag: :tag_name }, :created_user, :deleted_user)
 
     events = []
     pts.each do |pt|
       events << Event.new(
           post:         pt.post,
-          tag:          pt.tag,
+          tag:          pt.tag.as_json(only: [:id, :category], methods: [:name]),
           user:         pt.created_user && { id: pt.created_user.id, name: pt.created_user.name },
           change_type:  'add',
           timestamp:    pt.created_at)
@@ -167,7 +166,7 @@ class PostsController < ApplicationController
       if pt.discarded_at
         events << Event.new(
             post:         pt.post,
-            tag:          pt.tag,
+            tag:          pt.tag.as_json(only: [:id, :category], methods: [:name]),
             user:         pt.deleted_user && { id: pt.deleted_user.id, name: pt.deleted_user.name },
             change_type:  'remove',
             timestamp:    pt.discarded_at)
@@ -192,15 +191,15 @@ class PostsController < ApplicationController
   end
 
   def filter_posts_by_tags tag_names, match_type
-    posts = Post.joins(:tags)
+    posts = Post.joins(tags: :tag_name)
+
     if match_type == 'any'
-      posts = posts.where(tags: { name: tag_names }).distinct
+      posts.where(tag_names: { name: tag_names }).distinct
     else
-      tag_names.each do |tag|
-        posts = posts.where(id: Post.joins(:tags).where(tags: { name: tag }))
-      end
+      posts.where(tag_names: { name: tag_names })
+           .group('posts.id')
+           .having('COUNT(DISTINCT tag_names.id) = ?', tag_names.uniq.size)
     end
-    posts.distinct
   end
 
   def sync_post_tags! post, desired_tags
@@ -251,7 +250,8 @@ class PostsController < ApplicationController
       return nil unless tag
 
       if path.include?(tag_id)
-        return tag.as_json(only: [:id, :name, :category, :post_count]).merge(children: [])
+        return tag.as_json(only: [:id, :category, :post_count],
+                           methods: [:name]).merge(children: [])
       end
 
       if memo.key?(tag_id)
@@ -263,7 +263,8 @@ class PostsController < ApplicationController
 
       children = child_ids.filter_map { |cid| build_node.(cid, new_path) }
 
-      memo[tag_id] = tag.as_json(only: [:id, :name, :category, :post_count]).merge(children:)
+      memo[tag_id] = tag.as_json(only: [:id, :category, :post_count],
+                                 methods: [:name]).merge(children:)
     end
 
     root_ids.filter_map { |id| build_node.call(id, []) }

backend/app/controllers/tags_controller.rb

@@ -1,35 +1,41 @@
 class TagsController < ApplicationController
   def index
     post_id = params[:post]
-    tags = if post_id.present?
-             Tag.joins(:posts).where(posts: { id: post_id })
-           else
-             Tag.all
-           end
-    render json: tags
+
+    tags =
+        if post_id.present?
+          Tag.joins(:posts).where(posts: { id: post_id })
+        else
+          Tag.all
+        end
+
+    render json: tags.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
   end
 
   def autocomplete
     q = params[:q].to_s.strip
     return render json: [] if q.blank?
 
-    tags = (Tag
-            .where('(category = ? AND name LIKE ?) OR name LIKE ?',
+    tags = (Tag.joins(:tag_name).includes(:tag_name)
+            .where('(tags.category = ? AND tag_names.name LIKE ?) OR tag_names.name LIKE ?',
                    'nico', "nico:#{ q }%", "#{ q }%")
-            .order('post_count DESC, name ASC')
+            .order(Arel.sql('post_count DESC, tag_names.name ASC'))
             .limit(20))
-    render json: tags
+    render json: tags.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
   end
 
   def show
-    tag = Tag.find(params[:id])
-    render json: tag
+    tag = Tag.find_by(id: params[:id])
+    render json: tag.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
   end
 
   def show_by_name
-    tag = Tag.find_by(name: params[:name])
+    name = params[:name].to_s.strip
+    return head :bad_request if name.blank?
+
+    tag = Tag.joins(:tag_name).includes(:tag_name).find_by(tag_names: { name: })
     if tag
-      render json: tag
+      render json: tag.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
     else
       head :not_found
     end

backend/app/controllers/wiki_pages_controller.rb

@@ -2,19 +2,25 @@ class WikiPagesController < ApplicationController
   rescue_from Wiki::Commit::Conflict, with: :render_wiki_conflict
 
   def index
-    render json: WikiPage.all
+    pages = WikiPage.all
+    render json: pages.as_json(methods: [:title])
   end
 
   def show
-    render_wiki_page_or_404 WikiPage.find(params[:id])
+    page = WikiPage.find_by(id: params[:id])
+    render_wiki_page_or_404 page
   end
 
   def show_by_title
-    render_wiki_page_or_404 WikiPage.find_by(title: params[:title])
+    title = params[:title].to_s.strip
+    page = WikiPage.joins(:tag_name)
+                   .includes(:tag_name)
+                   .find_by(tag_names: { name: title })
+    render_wiki_page_or_404 page
   end
 
   def exists
-    if WikiPage.exists?(params[:id])
+    if WikiPage.exists?(id: params[:id])
       head :no_content
     else
       head :not_found
@@ -22,7 +28,8 @@ class WikiPagesController < ApplicationController
   end
 
   def exists_by_title
-    if WikiPage.exists?(title: params[:title])
+    title = params[:title].to_s.strip
+    if WikiPage.joins(:tag_name).exists?(tag_names: { name: title })
       head :no_content
     else
       head :not_found
@@ -81,7 +88,7 @@ class WikiPagesController < ApplicationController
       message = params[:message].presence
       Wiki::Commit.content!(page:, body:, created_user: current_user, message:)
 
-      render json: page, status: :created
+      render json: page.as_json(methods: [:title]), status: :created
     else
       render json: { errors: page.errors.full_messages },
              status: :unprocessable_entity
@@ -115,14 +122,14 @@ class WikiPagesController < ApplicationController
   end
 
   def search
-    title = params[:title]&.strip
+    title = params[:title].to_s.strip
 
-    q = WikiPage.all
+    q = WikiPage.joins(:tag_name).includes(:tag_name)
     if title.present?
-      q = q.where('title LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%")
+      q = q.where('tag_names.name LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%")
     end
 
-    render json: q.limit(20)
+    render json: q.limit(20).as_json(methods: [:title])
   end
 
   def changes
@@ -162,12 +169,14 @@ class WikiPagesController < ApplicationController
       pred = page.pred_revision_id(revision_id)
       succ = page.succ_revision_id(revision_id)
 
-      return render json: page.as_json.merge(body:, revision_id:, pred:, succ:)
+      return render json: page.as_json(methods: [:title])
+                              .merge(body:, revision_id:, pred:, succ:)
     end
 
     rev = page.current_revision
     unless rev
-      return render json: page.as_json.merge(body: nil, revision_id: nil, pred: nil, succ: nil)
+      return render json: page.as_json(methods: [:title])
+                              .merge(body: nil, revision_id: nil, pred: nil, succ: nil)
     end
 
     if rev.redirect?
@@ -181,7 +190,7 @@ class WikiPagesController < ApplicationController
     pred = page.pred_revision_id(revision_id)
     succ = page.succ_revision_id(revision_id)
 
-    render json: page.as_json.merge(body:, revision_id:, pred:, succ:)
+    render json: page.as_json(methods: [:title]).merge(body:, revision_id:, pred:, succ:)
   end
 
   def render_wiki_conflict err

backend/app/models/post_tag.rb

@@ -1,6 +1,10 @@
 class PostTag < ApplicationRecord
   include Discard::Model
 
+  before_destroy do
+    raise ActiveRecord::ReadOnlyRecord, '消さないでください．'
+  end
+
   belongs_to :post
   belongs_to :tag, counter_cache: :post_count
   belongs_to :created_user, class_name: 'User', optional: true

backend/app/models/tag.rb

@@ -21,6 +21,10 @@ class Tag < ApplicationRecord
                                        dependent: :destroy
   has_many :parents, through: :reversed_tag_implications, source: :parent_tag
 
+  belongs_to :tag_name
+  delegate :name, to: :tag_name, allow_nil: true
+  validates :tag_name, presence: true
+
   enum :category, { deerjikist:  'deerjikist',
                     meme:        'meme',
                     character:   'character',
@@ -29,7 +33,6 @@ class Tag < ApplicationRecord
                     nico:        'nico',
                     meta:        'meta' }
 
-  validates :name, presence: true, length: { maximum: 255 }
   validates :category, presence: true, inclusion: { in: Tag.categories.keys }
 
   validate :nico_tag_name_must_start_with_nico
@@ -44,31 +47,35 @@ class Tag < ApplicationRecord
       'mtr:'  => 'material',
       'meta:' => 'meta' }.freeze
 
+  def name= val
+    (self.tag_name ||= build_tag_name).name = val
+  end
+
+  def has_wiki
+    tag_name&.wiki_page.present?
+  end
+
   def self.tagme
-    @tagme ||= Tag.find_or_create_by!(name: 'タグ希望') do |tag|
-      tag.category = 'meta'
-    end
+    @tagme ||= find_or_create_by_tag_name!('タグ希望', category: 'meta')
   end
 
   def self.bot
-    @bot ||= Tag.find_or_create_by!(name: 'bot操作') do |tag|
-      tag.category = 'meta'
-    end
+    @bot ||= find_or_create_by_tag_name!('bot操作', category: 'meta')
   end
 
   def self.normalise_tags tag_names, with_tagme: true
     tags = tag_names.map do |name|
       pf, cat = CATEGORY_PREFIXES.find { |p, _| name.start_with?(p) } || ['', nil]
       name.delete_prefix!(pf)
-      Tag.find_or_initialize_by(name:).tap do |tag|
+      find_or_create_by_tag_name!(name, category: (cat || 'general')).tap do |tag|
         if cat && tag.category != cat
-          tag.category = cat
-          tag.save!
+          tag.update!(category: cat)
         end
       end
     end
+
     tags << Tag.tagme if with_tagme && tags.size < 10 && tags.none?(Tag.tagme)
-    tags.uniq
+    tags.uniq(&:id)
   end
 
   def self.expand_parent_tags tags
@@ -94,11 +101,19 @@ class Tag < ApplicationRecord
     (result + tags).uniq { |t| t.id }
   end
 
+  def self.find_or_create_by_tag_name!(name, category:)
+    tn = TagName.find_or_create_by!(name: name.to_s.strip)
+    Tag.find_or_create_by!(tag_name_id: tn.id) do |t|
+      t.category = category
+    end
+  end
+
   private
 
   def nico_tag_name_must_start_with_nico
-    if ((category == 'nico' && !(name.start_with?('nico:'))) || 
-        (category != 'nico' && name.start_with?('nico:')))
+    n = name.to_s
+    if ((category == 'nico' && !(n.start_with?('nico:'))) || 
+        (category != 'nico' && n.start_with?('nico:')))
       errors.add :name, 'ニコニコ・タグの命名規則に反してゐます．'
     end
   end

backend/app/models/tag_name.rb

@@ -0,0 +1,9 @@
+class TagName < ApplicationRecord
+  has_one :tag
+  has_one :wiki_page
+
+  belongs_to :canonical, class_name: 'TagName', optional: true
+  has_many :aliases, class_name: 'TagName', foreign_key: :canonical_id
+
+  validates :name, presence: true, length: { maximum: 255 }, uniqueness: true
+end

backend/app/models/wiki_page.rb

@@ -11,7 +11,16 @@ class WikiPage < ApplicationRecord
            foreign_key: :redirect_page_id,
            dependent: :nullify
 
-  validates :title, presence: true, length: { maximum: 255 }, uniqueness: true
+  belongs_to :tag_name
+  validates :tag_name, presence: true
+
+  def title
+    tag_name.name
+  end
+
+  def title= val
+    (self.tag_name ||= build_tag_name).name = val
+  end
 
   def current_revision
     wiki_revisions.order(id: :desc).first

backend/db/migrate/20260111180600_create_tag_names.rb

@@ -0,0 +1,10 @@
+class CreateTagNames < ActiveRecord::Migration[7.0]
+  def change
+    create_table :tag_names do |t|
+      t.string :name, limit: 255, null: false
+      t.references :canonical, null: true, foreign_key: { to_table: :tag_names }, index: true
+      t.timestamps
+    end
+    add_index :tag_names, :name, unique: true
+  end
+end

backend/db/migrate/20260111192600_add_tag_name_to_tags.rb

@@ -0,0 +1,42 @@
+class AddTagNameToTags < ActiveRecord::Migration[7.0]
+  class Tag < ApplicationRecord
+    self.table_name = 'tags'
+  end
+
+  class TagName < ApplicationRecord
+    self.table_name = 'tag_names'
+  end
+
+  def up
+    add_reference :tags, :tag_name, null: true, foreign_key: true, index: false, after: :id
+    add_index :tags, :tag_name_id, unique: true
+
+    Tag.find_each do |tag|
+      name = tag.read_attribute(:name)
+      tn = TagName.find_or_create_by!(name:) do |r|
+        r.canonical_id = nil
+      end
+      tag.update_columns(tag_name_id: tn.id)
+    end
+
+    change_column_null :tags, :tag_name_id, false
+
+    remove_column :tags, :name
+  end
+
+  def down
+    add_column :tags, :name, :string, limit: 255, null: true, after: :id
+
+    Tag.find_each do |tag|
+      tag_name_id = tag.read_attribute(:tag_name_id)
+      name = TagName.find(tag_name_id).read_attribute(:name)
+      tag.update_columns(name:)
+    end
+
+    change_column_null :tags, :name, false
+
+    remove_foreign_key :tags, column: :tag_name_id
+    remove_index :tags, :tag_name_id
+    remove_column :tags, :tag_name_id
+  end
+end

backend/db/migrate/20260111204400_add_tag_name_to_wiki_pages.rb

@@ -0,0 +1,42 @@
+class AddTagNameToWikiPages < ActiveRecord::Migration[7.0]
+  class WikiPage < ApplicationRecord
+    self.table_name = 'wiki_pages'
+  end
+
+  class TagName < ApplicationRecord
+    self.table_name = 'tag_names'
+  end
+
+  def up
+    add_reference :wiki_pages, :tag_name, null: true, foreign_key: true, index: false, after: :id
+    add_index :wiki_pages, :tag_name_id, unique: true
+
+    WikiPage.find_each do |page|
+      name = page.read_attribute(:title)
+      tn = TagName.find_or_create_by!(name:) do |r|
+        r.canonical_id = nil
+      end
+      page.update_columns(tag_name_id: tn.id)
+    end
+
+    change_column_null :wiki_pages, :tag_name_id, false
+
+    remove_column :wiki_pages, :title
+  end
+
+  def down
+    add_column :wiki_pages, :title, :string, limit: 255, null: true, after: :id
+
+    WikiPage.find_each do |page|
+      tag_name_id = page.read_attribute(:tag_name_id)
+      title = TagName.find(tag_name_id).read_attribute(:name)
+      page.update_columns(title:)
+    end
+
+    change_column_null :wiki_pages, :title, false
+
+    remove_foreign_key :wiki_pages, column: :tag_name_id
+    remove_index :wiki_pages, :tag_name_id
+    remove_column :wiki_pages, :tag_name_id
+  end
+end

backend/db/migrate/20260112111800_drop_tag_aliases.rb

@@ -0,0 +1,9 @@
+class DropTagAliases < ActiveRecord::Migration[7.0]
+  def up
+    drop_table :tag_aliases
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
+ActiveRecord::Schema[8.0].define(version: 2026_01_12_111800) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -84,7 +84,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
   end
 
   create_table "posts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "title", null: false
+    t.string "title"
     t.string "url", limit: 2000, null: false
     t.string "thumbnail_base", limit: 2000
     t.bigint "parent_id"
@@ -106,14 +106,6 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
     t.index ["user_id"], name: "index_settings_on_user_id"
   end
 
-  create_table "tag_aliases", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "tag_id", null: false
-    t.string "name", null: false
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["tag_id"], name: "index_tag_aliases_on_tag_id"
-  end
-
   create_table "tag_implications", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_id", null: false
     t.bigint "parent_tag_id", null: false
@@ -124,6 +116,15 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
     t.index ["tag_id"], name: "index_tag_implications_on_tag_id"
   end
 
+  create_table "tag_names", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "name", null: false
+    t.bigint "canonical_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["canonical_id"], name: "index_tag_names_on_canonical_id"
+    t.index ["name"], name: "index_tag_names_on_name", unique: true
+  end
+
   create_table "tag_similarities", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_id", null: false
     t.bigint "target_tag_id", null: false
@@ -133,11 +134,12 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
   end
 
   create_table "tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "name", null: false
+    t.bigint "tag_name_id", null: false
     t.string "category", default: "general", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.integer "post_count", default: 0, null: false
+    t.index ["tag_name_id"], name: "index_tags_on_tag_name_id", unique: true
   end
 
   create_table "user_ips", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -176,12 +178,13 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
   end
 
   create_table "wiki_pages", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "title", null: false
+    t.bigint "tag_name_id", null: false
     t.bigint "created_user_id", null: false
     t.bigint "updated_user_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["created_user_id"], name: "index_wiki_pages_on_created_user_id"
+    t.index ["tag_name_id"], name: "index_wiki_pages_on_tag_name_id", unique: true
     t.index ["updated_user_id"], name: "index_wiki_pages_on_updated_user_id"
   end
 
@@ -228,15 +231,17 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
   add_foreign_key "posts", "posts", column: "parent_id"
   add_foreign_key "posts", "users", column: "uploaded_user_id"
   add_foreign_key "settings", "users"
-  add_foreign_key "tag_aliases", "tags"
   add_foreign_key "tag_implications", "tags"
   add_foreign_key "tag_implications", "tags", column: "parent_tag_id"
+  add_foreign_key "tag_names", "tag_names", column: "canonical_id"
   add_foreign_key "tag_similarities", "tags"
   add_foreign_key "tag_similarities", "tags", column: "target_tag_id"
+  add_foreign_key "tags", "tag_names"
   add_foreign_key "user_ips", "ip_addresses"
   add_foreign_key "user_ips", "users"
   add_foreign_key "user_post_views", "posts"
   add_foreign_key "user_post_views", "users"
+  add_foreign_key "wiki_pages", "tag_names"
   add_foreign_key "wiki_pages", "users", column: "created_user_id"
   add_foreign_key "wiki_pages", "users", column: "updated_user_id"
   add_foreign_key "wiki_revision_lines", "wiki_lines"

backend/lib/tasks/sync_nico.rake

@@ -4,6 +4,7 @@ namespace :nico do
     require 'open3'
     require 'open-uri'
     require 'nokogiri'
+    require 'set'
 
     fetch_thumbnail = -> url do
       html = URI.open(url, read_timeout: 60, 'User-Agent' => 'Mozilla/5.0').read
@@ -12,9 +13,9 @@ namespace :nico do
       doc.at('meta[name="thumbnail"]')&.[]('content').presence
     end
 
-    def sync_post_tags! post, desired_tag_ids
+    def sync_post_tags! post, desired_tag_ids, current_ids: nil
+      current_ids ||= PostTag.kept.where(post_id: post.id).pluck(:tag_id).to_set
       desired_ids = desired_tag_ids.compact.to_set
-      current_ids = post.tags.pluck(:id).to_set
 
       to_add = desired_ids - current_ids
       to_remove = current_ids - desired_ids
@@ -43,12 +44,12 @@ namespace :nico do
 
     data = JSON.parse(stdout)
     data.each do |datum|
-      post = Post.where('url LIKE ?', '%nicovideo.jp%').find { |post|
-        post.url =~ %r{#{ Regexp.escape(datum['code']) }(?!\d)}
-      }
+      code = datum['code']
+      post = Post.where('url REGEXP ?', "nicovideo\\.jp/watch/#{ Regexp.escape(code) }([^0-9]|$)")
+                 .first
       unless post
         title = datum['title']
-        url = "https://www.nicovideo.jp/watch/#{ datum['code'] }"
+        url = "https://www.nicovideo.jp/watch/#{ code }"
         thumbnail_base = fetch_thumbnail.(url) rescue nil
         post = Post.new(title:, url:, thumbnail_base:, uploaded_user: nil)
         if thumbnail_base.present?
@@ -62,21 +63,19 @@ namespace :nico do
         sync_post_tags!(post, [Tag.tagme.id])
       end
 
-      kept_tags = post.tags.reload
-      kept_non_nico_ids = kept_tags.where.not(category: 'nico').pluck(:id).to_set
+      kept_ids = PostTag.kept.where(post_id: post.id).pluck(:tag_id).to_set
+      kept_non_nico_ids = post.tags.where.not(category: 'nico').pluck(:id).to_set
 
       desired_nico_ids = []
       desired_non_nico_ids = []
       datum['tags'].each do |raw|
         name = "nico:#{ raw }"
-        tag = Tag.find_or_initialize_by(name:) do |t|
-          t.category = 'nico'
-        end
-        tag.save! if tag.new_record?
+        tag = Tag.find_or_create_by_tag_name!(name, category: 'nico')
         desired_nico_ids << tag.id
-        unless tag.in?(kept_tags)
-          desired_non_nico_ids.concat(tag.linked_tags.pluck(:id))
-          desired_nico_ids.concat(tag.linked_tags.pluck(:id))
+        unless tag.id.in?(kept_ids)
+          linked_ids = tag.linked_tags.pluck(:id)
+          desired_non_nico_ids.concat(linked_ids)
+          desired_nico_ids.concat(linked_ids)
         end
       end
       desired_nico_ids.uniq!
@@ -89,7 +88,7 @@ namespace :nico do
       end
       desired_all_ids.uniq!
 
-      sync_post_tags!(post, desired_all_ids)
+      sync_post_tags!(post, desired_all_ids, current_ids: kept_ids)
     end
   end
 end