#442

backend/Gemfile

@@ -71,3 +71,5 @@ gem "rspec-rails", "~> 8.0", :groups => [:development, :test]
 gem 'aws-sdk-s3', require: false
 
 gem 'rails-i18n', '~> 8.0.0'
+
+gem "json", "~> 2.19.9"

backend/Gemfile.lock

@@ -1,29 +1,29 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (8.0.2)
+    actioncable (8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
       zeitwerk (~> 2.6)
-    actionmailbox (8.0.2)
+    actionmailbox (8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      activejob (= 8.0.2)
+      activejob (= 8.0.5.1)
-      activerecord (= 8.0.2)
+      activerecord (= 8.0.5.1)
-      activestorage (= 8.0.2)
+      activestorage (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       mail (>= 2.8.0)
-    actionmailer (8.0.2)
+    actionmailer (8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      actionview (= 8.0.2)
+      actionview (= 8.0.5.1)
-      activejob (= 8.0.2)
+      activejob (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (8.0.2)
+    actionpack (8.0.5.1)
-      actionview (= 8.0.2)
+      actionview (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       nokogiri (>= 1.8.5)
       rack (>= 2.2.4)
       rack-session (>= 1.0.1)
@@ -31,35 +31,35 @@ GEM
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actiontext (8.0.2)
+    actiontext (8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      activerecord (= 8.0.2)
+      activerecord (= 8.0.5.1)
-      activestorage (= 8.0.2)
+      activestorage (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (8.0.2)
+    actionview (8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (8.0.2)
+    activejob (8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       globalid (>= 0.3.6)
-    activemodel (8.0.2)
+    activemodel (8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
-    activerecord (8.0.2)
+    activerecord (8.0.5.1)
-      activemodel (= 8.0.2)
+      activemodel (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       timeout (>= 0.4.0)
-    activestorage (8.0.2)
+    activestorage (8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      activejob (= 8.0.2)
+      activejob (= 8.0.5.1)
-      activerecord (= 8.0.2)
+      activerecord (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       marcel (~> 1.0)
-    activesupport (8.0.2)
+    activesupport (8.0.5.1)
       base64
       benchmark (>= 0.3)
       bigdecimal
@@ -92,22 +92,22 @@ GEM
       aws-sigv4 (~> 1.5)
     aws-sigv4 (1.12.1)
       aws-eventstream (~> 1, >= 1.0.2)
-    base64 (0.2.0)
+    base64 (0.3.0)
     bcrypt_pbkdf (1.1.1)
     bcrypt_pbkdf (1.1.1-arm64-darwin)
     bcrypt_pbkdf (1.1.1-x86_64-darwin)
-    benchmark (0.4.0)
+    benchmark (0.5.0)
-    bigdecimal (3.1.9)
+    bigdecimal (4.1.3)
     bootsnap (1.18.6)
       msgpack (~> 1.2)
     brakeman (7.0.2)
       racc
     builder (3.3.0)
     chronic (0.10.2)
-    concurrent-ruby (1.3.5)
+    concurrent-ruby (1.3.8)
-    connection_pool (2.5.3)
+    connection_pool (3.0.2)
-    crass (1.0.6)
+    crass (1.0.7)
-    date (3.4.1)
+    date (3.6.0)
     diff-lcs (1.6.2)
     discard (1.4.0)
       activerecord (>= 4.2, < 9.0)
@@ -115,8 +115,9 @@ GEM
     dotenv-rails (3.1.8)
       dotenv (= 3.1.8)
       railties (>= 6.1)
-    drb (2.2.1)
+    drb (2.2.3)
     ed25519 (1.4.0)
+    erb (6.0.7)
     erubi (1.13.1)
     factory_bot (6.5.6)
       activesupport (>= 6.1.0)
@@ -134,7 +135,7 @@ GEM
     gemojione (4.3.3)
       json
     github-markup (4.0.2)
-    globalid (1.2.1)
+    globalid (1.4.0)
       activesupport (>= 6.1)
     gollum (6.1.0)
       gemojione (~> 4.1)
@@ -166,19 +167,20 @@ GEM
     gollum-rugged_adapter (3.0)
       mime-types (~> 3.4)
       rugged (~> 1.5)
-    i18n (1.14.7)
+    i18n (1.15.2)
       concurrent-ruby (~> 1.0)
     image_processing (1.14.0)
       mini_magick (>= 4.9.5, < 6)
       ruby-vips (>= 2.0.17, < 3)
-    io-console (0.8.0)
+    io-console (0.9.4)
-    irb (1.15.2)
+    irb (1.18.0)
       pp (>= 0.6.0)
+      prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
     jmespath (1.6.2)
-    json (2.12.0)
+    json (2.19.9)
-    jwt (2.10.1)
+    jwt (3.3.0)
       base64
     kamal (2.6.1)
       activesupport (>= 7.0)
@@ -198,15 +200,16 @@ GEM
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
     logger (1.7.0)
-    loofah (2.24.1)
+    loofah (2.25.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mail (2.8.1)
+    mail (2.9.1)
+      logger
       mini_mime (>= 0.1.1)
       net-imap
       net-pop
       net-smtp
-    marcel (1.0.4)
+    marcel (1.2.1)
     mime-types (3.7.0)
       logger
       mime-types-data (~> 3.2025, >= 3.2025.0507)
@@ -215,45 +218,46 @@ GEM
       benchmark
       logger
     mini_mime (1.1.5)
-    minitest (5.25.5)
+    minitest (6.0.6)
-    msgpack (1.8.0)
+      drb (~> 2.0)
-    multi_json (1.15.0)
+      prism (~> 1.5)
+    msgpack (1.8.5)
+    multi_json (1.21.2)
     mustache (1.1.1)
     mustache-sinatra (2.0.0)
       mustache (~> 1.0)
-    mustermann (3.0.3)
+    mustermann (3.1.1)
-      ruby2_keywords (~> 0.0.1)
     mysql2 (0.5.6)
-    net-imap (0.5.8)
+    net-imap (0.6.8)
       date
       net-protocol
     net-pop (0.1.2)
       net-protocol
-    net-protocol (0.2.2)
+    net-protocol (0.4.0)
       timeout
     net-scp (4.1.0)
       net-ssh (>= 2.6.5, < 8.0.0)
     net-sftp (4.0.0)
       net-ssh (>= 5.0.0, < 8.0.0)
-    net-smtp (0.5.1)
+    net-smtp (0.5.2)
       net-protocol
     net-ssh (7.3.0)
-    nio4r (2.7.4)
+    nio4r (2.7.5)
-    nokogiri (1.18.8-aarch64-linux-gnu)
+    nokogiri (1.19.4-aarch64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-aarch64-linux-musl)
+    nokogiri (1.19.4-aarch64-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm-linux-gnu)
+    nokogiri (1.19.4-arm-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm-linux-musl)
+    nokogiri (1.19.4-arm-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm64-darwin)
+    nokogiri (1.19.4-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-darwin)
+    nokogiri (1.19.4-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-linux-gnu)
+    nokogiri (1.19.4-x86_64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-linux-musl)
+    nokogiri (1.19.4-x86_64-linux-musl)
       racc (~> 1.4)
     octicons (19.15.2)
     ostruct (0.6.1)
@@ -261,70 +265,73 @@ GEM
     parser (3.3.8.0)
       ast (~> 2.4.1)
       racc
-    pp (0.6.2)
+    pp (0.6.4)
       prettyprint
-    prettyprint (0.2.0)
+    prettyprint (0.2.1)
-    prism (1.4.0)
+    prism (1.9.0)
-    psych (5.2.6)
+    psych (5.5.0)
       date
       stringio
     puma (6.6.0)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (3.1.14)
+    rack (3.2.7)
     rack-cors (2.0.2)
       rack (>= 2.0.0)
-    rack-protection (4.1.1)
+    rack-protection (4.2.1)
       base64 (>= 0.1.0)
       logger (>= 1.6.0)
       rack (>= 3.0.0, < 4)
-    rack-session (2.1.1)
+    rack-session (2.1.2)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
-    rack-test (2.2.0)
+    rack-test (2.3.0)
       rack (>= 1.3)
-    rackup (2.2.1)
+    rackup (2.3.1)
       rack (>= 3)
-    rails (8.0.2)
+    rails (8.0.5.1)
-      actioncable (= 8.0.2)
+      actioncable (= 8.0.5.1)
-      actionmailbox (= 8.0.2)
+      actionmailbox (= 8.0.5.1)
-      actionmailer (= 8.0.2)
+      actionmailer (= 8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      actiontext (= 8.0.2)
+      actiontext (= 8.0.5.1)
-      actionview (= 8.0.2)
+      actionview (= 8.0.5.1)
-      activejob (= 8.0.2)
+      activejob (= 8.0.5.1)
-      activemodel (= 8.0.2)
+      activemodel (= 8.0.5.1)
-      activerecord (= 8.0.2)
+      activerecord (= 8.0.5.1)
-      activestorage (= 8.0.2)
+      activestorage (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       bundler (>= 1.15.0)
-      railties (= 8.0.2)
+      railties (= 8.0.5.1)
-    rails-dom-testing (2.2.0)
+    rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.6.2)
+    rails-html-sanitizer (1.7.1)
-      loofah (~> 2.21)
+      loofah (~> 2.25, >= 2.25.2)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
     rails-i18n (8.0.2)
       i18n (>= 0.7, < 2)
       railties (>= 8.0.0, < 9)
-    railties (8.0.2)
+    railties (8.0.5.1)
-      actionpack (= 8.0.2)
+      actionpack (= 8.0.5.1)
-      activesupport (= 8.0.2)
+      activesupport (= 8.0.5.1)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
+      tsort (>= 0.2)
       zeitwerk (~> 2.6)
     rainbow (3.1.1)
-    rake (13.2.1)
+    rake (13.4.2)
-    rdoc (6.13.1)
+    rdoc (6.17.0)
+      erb
       psych (>= 4.0.0)
-    regexp_parser (2.10.0)
+      tsort
-    reline (0.6.1)
+    regexp_parser (2.13.1)
+    reline (0.7.0)
       io-console (~> 0.5)
-    rexml (3.4.1)
+    rexml (3.4.4)
     rouge (3.30.0)
     rspec-core (3.13.6)
       rspec-support (~> 3.13.0)
@@ -345,20 +352,20 @@ GEM
     rspec-support (3.13.6)
     rss (0.3.1)
       rexml
-    rubocop (1.75.6)
+    rubocop (1.92.0)
-      json (~> 2.3)
+      json (>= 2.3)
       language_server-protocol (~> 3.17.0.2)
       lint_roller (~> 1.1.0)
-      parallel (~> 1.10)
+      parallel (>= 1.10)
       parser (>= 3.3.0.2)
       rainbow (>= 2.2.2, < 4.0)
-      regexp_parser (>= 2.9.3, < 3.0)
+      regexp_parser (>= 2.11.3, < 3.0)
-      rubocop-ast (>= 1.44.0, < 2.0)
+      rubocop-ast (>= 1.49.0, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 2.4.0, < 4.0)
-    rubocop-ast (1.44.1)
+    rubocop-ast (1.50.0)
       parser (>= 3.3.7.2)
-      prism (~> 1.4)
+      prism (~> 1.7)
     rubocop-performance (1.25.0)
       lint_roller (~> 1.1)
       rubocop (>= 1.75.0, < 2.0)
@@ -377,24 +384,23 @@ GEM
     ruby-vips (2.2.3)
       ffi (~> 1.12)
       logger
-    ruby2_keywords (0.0.5)
     rugged (1.9.0)
     securerandom (0.4.1)
-    sinatra (4.1.1)
+    sinatra (4.2.1)
       logger (>= 1.6.0)
       mustermann (~> 3.0)
       rack (>= 3.0.0, < 4)
-      rack-protection (= 4.1.1)
+      rack-protection (= 4.2.1)
       rack-session (>= 2.0.0, < 3)
       tilt (~> 2.0)
-    sinatra-contrib (4.1.1)
+    sinatra-contrib (4.2.1)
       multi_json (>= 0.0.2)
       mustermann (~> 3.0)
-      rack-protection (= 4.1.1)
+      rack-protection (= 4.2.1)
-      sinatra (= 4.1.1)
+      sinatra (= 4.2.1)
       tilt (~> 2.0)
-    sprockets (4.2.2)
+    sprockets (4.4.1)
-      concurrent-ruby (~> 1.0)
+      concurrent-ruby (~> 1.1)
       logger
       rack (>= 2.2.4, < 4)
     sprockets-helpers (1.4.0)
@@ -403,14 +409,14 @@ GEM
       actionpack (>= 6.1)
       activesupport (>= 6.1)
       sprockets (>= 3.0.0)
-    sqlite3 (2.6.0-aarch64-linux-gnu)
+    sqlite3 (2.10.1-aarch64-linux-gnu)
-    sqlite3 (2.6.0-aarch64-linux-musl)
+    sqlite3 (2.10.1-aarch64-linux-musl)
-    sqlite3 (2.6.0-arm-linux-gnu)
+    sqlite3 (2.10.1-arm-linux-gnu)
-    sqlite3 (2.6.0-arm-linux-musl)
+    sqlite3 (2.10.1-arm-linux-musl)
-    sqlite3 (2.6.0-arm64-darwin)
+    sqlite3 (2.10.1-arm64-darwin)
-    sqlite3 (2.6.0-x86_64-darwin)
+    sqlite3 (2.10.1-x86_64-darwin)
-    sqlite3 (2.6.0-x86_64-linux-gnu)
+    sqlite3 (2.10.1-x86_64-linux-gnu)
-    sqlite3 (2.6.0-x86_64-linux-musl)
+    sqlite3 (2.10.1-x86_64-linux-musl)
     sshkit (1.24.0)
       base64
       logger
@@ -418,18 +424,19 @@ GEM
       net-sftp (>= 2.1.2)
       net-ssh (>= 2.8.0)
       ostruct
-    stringio (3.1.7)
+    stringio (3.2.0)
     therubyrhino (2.1.2)
       therubyrhino_jar (>= 1.7.4, < 1.7.9)
     therubyrhino_jar (1.7.8)
-    thor (1.3.2)
+    thor (1.5.0)
     thruster (0.1.13)
     thruster (0.1.13-aarch64-linux)
     thruster (0.1.13-arm64-darwin)
     thruster (0.1.13-x86_64-darwin)
     thruster (0.1.13-x86_64-linux)
-    tilt (2.6.0)
+    tilt (2.9.0)
-    timeout (0.4.3)
+    timeout (0.6.1)
+    tsort (0.2.0)
     twitter-text (1.14.7)
       unf (~> 0.1.0)
     tzinfo (2.0.6)
@@ -440,16 +447,16 @@ GEM
     unicode-display_width (3.1.4)
       unicode-emoji (~> 4.0, >= 4.0.4)
     unicode-emoji (4.0.4)
-    uri (1.0.3)
+    uri (1.1.2)
     useragent (0.16.11)
     webrick (1.9.1)
-    websocket-driver (0.7.7)
+    websocket-driver (0.8.2)
       base64
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
     whenever (1.0.0)
       chronic (>= 0.6.3)
-    zeitwerk (2.7.2)
+    zeitwerk (2.8.3)
 
 PLATFORMS
   aarch64-linux
@@ -473,6 +480,7 @@ DEPENDENCIES
   factory_bot_rails
   gollum
   image_processing (~> 1.14)
+  json (~> 2.19.9)
   jwt
   kamal
   mysql2 (~> 0.5.6)

backend/app/controllers/post_versions_controller.rb

@@ -14,8 +14,9 @@ class PostVersionsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    q = HistoryAccess.visible(version_scope)
+    q = HistoryAccess.visible(PostVersion.all)
     q = q.where('post_versions.post_id = ?', post_id) if post_id
+    q = q.with_previous_version if tag_id || external_tag_id
     if external_tag_id || (tag_id && !(Tag.exists?(id: tag_id)))
       q = q.where('JSON_CONTAINS(post_versions.tags_json,' +
                   "JSON_OBJECT('external_tag_id', #{ external_tag_id || tag_id })) " +
@@ -28,9 +29,12 @@ class PostVersionsController < ApplicationController
 
     count = q.except(:select, :order, :limit, :offset).count
 
-    versions = q.order(Arel.sql('post_versions.created_at DESC, post_versions.id DESC'))
+    ids = q.order(Arel.sql('post_versions.created_at DESC, post_versions.id DESC'))
                 .limit(limit)
                 .offset(offset)
+                .pluck('post_versions.id')
+    versions = version_scope.merge(q).where(id: ids)
+        .order(Arel.sql('post_versions.created_at DESC, post_versions.id DESC'))
 
     render json: { versions: serialise_versions(versions, locale.language_code), count:, population_count: HistoryAccess.population_count(PostVersion) }
   end

backend/app/controllers/posts_controller.rb

@@ -37,20 +37,10 @@ class PostsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    pt_max_sql =
+    needs_history_join = order[0] == 'updated_at' || updated_between.any?(&:present?)
-        HistoryAccess.visible(PostVersion.all)
-        .select('post_id, MAX(created_at) AS max_updated_at')
-        .group('post_id')
-        .to_sql
-
-    updated_at_all_sql =
-        'GREATEST(posts.updated_at,' +
-        'COALESCE(pt_max.max_updated_at, posts.updated_at))'
 
     q =
         filtered_posts(locale)
-        .joins("LEFT JOIN (#{ pt_max_sql }) pt_max ON pt_max.post_id = posts.id")
-        .reselect('posts.*', Arel.sql("#{ updated_at_all_sql } AS updated_at_all"))
         .preload(:external_tags, :uploaded_user, :parents, :children,
                  post_tags: [:sections, { tag: [:deerjikists, :materials,
                                                 :tag_names, :tag_descriptions] }])
@@ -66,12 +56,25 @@ class PostsController < ApplicationController
     end
     q = q.where('posts.created_at >= ?', created_between[0]) if created_between[0]
     q = q.where('posts.created_at <= ?', created_between[1]) if created_between[1]
+    count_scope = q
+    if needs_history_join
+      history_times = HistoryAccess.visible(PostVersion.all)
+          .select('post_id, MAX(created_at) AS latest_at').group(:post_id)
+      q = q.joins("LEFT JOIN (#{ history_times.to_sql }) history_times " +
+                  'ON history_times.post_id = posts.id')
+      updated_at_all_sql = 'GREATEST(posts.updated_at, ' +
+          'COALESCE(history_times.latest_at, posts.updated_at))'
+    end
     if updated_between[0]
       q = q.where("#{ updated_at_all_sql } >= ?", updated_between[0])
     end
     if updated_between[1]
       q = q.where("#{ updated_at_all_sql } <= ?", updated_between[1])
     end
+    count_scope = q if updated_between.any?(&:present?)
+    if needs_history_join
+      q = q.select('posts.*', "#{ updated_at_all_sql } AS updated_at")
+    end
 
     sort_sql =
         case order[0]
@@ -88,12 +91,20 @@ class PostsController < ApplicationController
              .limit(limit)
              .offset(offset)
              .to_a
+    latest_version_times =
+        if needs_history_join
+          { }
+        else
+          HistoryAccess.visible(PostVersion.where(post_id: posts.map(&:id)))
+              .group(:post_id).maximum(:created_at)
+        end
 
-    q = q.except(:select, :order)
+    count_scope = count_scope.except(:select, :order)
 
     render json: { posts: posts.map { |post|
+      updated_at = [post.updated_at, latest_version_times[post.id]].compact.max
       PostRepr.base(post, language_code: locale.language_code)
-              .merge(updated_at: post.updated_at_all).tap do |json|
+          .merge('updated_at' => updated_at).tap do |json|
         json['thumbnail'] =
             if post.thumbnail.attached?
               rails_storage_proxy_url(post.thumbnail, only_path: false)
@@ -101,7 +112,7 @@ class PostsController < ApplicationController
               nil
             end
       end
-    }, count: q.group_values.present? ? q.count.size : q.count }
+    }, count: count_scope.group_values.present? ? count_scope.count.size : count_scope.count }
   end
 
   def random

backend/app/models/history_access.rb

@@ -59,20 +59,21 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
   end
 
   def self.json_reference(table, key, document)
-    "NOT EXISTS (SELECT 1 FROM JSON_TABLE(COALESCE(#{ document }, JSON_ARRAY()), " +
+    # A scalar lookup avoids MySQL's semijoin rewrite losing the JSON row correlation.
+    "(SELECT 1 FROM JSON_TABLE(COALESCE(#{ document }, JSON_ARRAY()), " +
         "'$[*]' COLUMNS (reference_id BIGINT PATH '$' NULL ON EMPTY)) reference_entry " +
         "JOIN (#{ discarded_keys(table, key) }) blocked " +
-        "ON reference_entry.reference_id = blocked.#{ key })"
+        "ON reference_entry.reference_id = blocked.#{ key } LIMIT 1) IS NULL"
   end
 
   def self.list_reference(table, key, document)
     # Preserve FIND_IN_SET's exact token semantics, including empty tokens.
     array = "CONCAT('[', REPLACE(JSON_QUOTE(REPLACE(COALESCE(#{ document }, ''), " +
         "' ', ',')), ',', '\",\"'), ']')"
-    "NOT EXISTS (SELECT 1 FROM JSON_TABLE(#{ array }, '$[*]' " +
+    "(SELECT 1 FROM JSON_TABLE(#{ array }, '$[*]' " +
         "COLUMNS (reference_id VARCHAR(255) PATH '$')) reference_entry " +
         "JOIN (#{ discarded_keys(table, key) }) blocked " +
-        "ON reference_entry.reference_id = CAST(blocked.#{ key } AS CHAR))"
+        "ON reference_entry.reference_id = CAST(blocked.#{ key } AS CHAR) LIMIT 1) IS NULL"
   end
 
   def self.snapshot_reference(model, row, external: false)
@@ -91,8 +92,8 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
       match += ' AND reference_version.version_no = tag_reference.version_no'
       latest = ''
     end
-    "NOT EXISTS (SELECT 1 FROM #{ source } JOIN #{ table } reference_version ON #{ match } " +
+    "(SELECT 1 FROM #{ source } JOIN #{ table } reference_version ON #{ match } " +
-        "WHERE NOT (#{ sql(model, 'reference_version') }) #{ latest })"
+        "WHERE NOT (#{ sql(model, 'reference_version') }) #{ latest } LIMIT 1) IS NULL"
   end
 
   def self.reference_sql(table, row)
@@ -109,11 +110,15 @@ class HistoryAccess < ActiveSupport::CurrentAttributes
       # conservatively; never expose a private linked name through an external tag.
       names = "JSON_MERGE_PRESERVE(JSON_ARRAY(private_tag.name), " +
           "COALESCE(JSON_EXTRACT(private_tag.names, '$**.name'), JSON_ARRAY()))"
-      ["NOT EXISTS (SELECT 1 FROM tag_versions private_tag " +
+      # DISTINCT prevents merging this independent name set into the correlated scan.
+      # Keep byte-distinct names even when the column collation considers them equal.
+      private_names = 'SELECT DISTINCT private_name.name, ' +
+          'CAST(private_name.name AS BINARY) AS name_bytes FROM tag_versions private_tag ' +
           "JOIN (#{ discarded_keys('tag_versions', 'tag_id') }) blocked " +
-          "ON blocked.tag_id = private_tag.tag_id " +
+          'ON blocked.tag_id = private_tag.tag_id ' +
           "JOIN JSON_TABLE(#{ names }, '$[*]' COLUMNS (name TEXT PATH '$')) private_name " +
-          "WHERE private_name.name <> '' AND " +
+          "WHERE private_name.name <> ''"
+      ["NOT EXISTS (SELECT 1 FROM (#{ private_names }) private_name WHERE " +
           "LOCATE(CONCAT(' ', private_name.name, ' '), " +
           "CONCAT(' ', COALESCE(#{ row }.linked_tags, ''), ' ')) > 0)"]
     when 'tag_versions'

backend/spec/requests/post_history_privacy_spec.rb

@@ -0,0 +1,129 @@
+require 'rails_helper'
+
+RSpec.describe 'Post history privacy', type: :request do
+  let(:origin) { Time.utc(2020, 1, 1) }
+  let!(:post_record) do
+    create(:post, title: 'current', created_at: origin, updated_at: origin)
+  end
+  let!(:other_post) do
+    create(:post, created_at: origin, updated_at: origin + 3.days + 1.hour)
+  end
+  let!(:tag) { create(:tag, primary_name: 'private-history-tag') }
+  let!(:external) { create(:external_tag, name: 'external-history-tag') }
+
+  before do
+    ['create', 'discard'].each_with_index do |event, index|
+      TagVersion.create!(tag:, version_no: index + 1, event_type: event,
+          name: 'private-history-tag', category: 'general', aliases: '', parent_tag_ids: '',
+          names: { ja: { name: 'private-history-tag', script_code: 'Jpan',
+                         auto_generated: false, aliases: [] } },
+          created_at: origin + index.hours)
+    end
+    NicoTagVersion.create!(external_tag: external, version_no: 1, event_type: 'create',
+        name: 'nico:external-history-tag', linked_tags: 'private-history-tag',
+        created_at: origin)
+    ['create', 'discard', 'restore', 'update'].each_with_index do |event, index|
+      snapshots =
+          if index < 2
+            [{ tag_id: tag.id, version_no: 1, name: 'private-history-tag', sections: [] }]
+          elsif index == 3
+            [{ external_tag_id: external.id }]
+          else
+            []
+          end
+      PostVersion.create!(post: post_record, version_no: index + 1, event_type: event,
+          title: "version #{ index + 1 }", url: post_record.url, tags: '',
+          tags_json: snapshots, parent_post_ids: '', created_at: origin + (index + 1).days)
+    end
+  end
+
+  it 'evaluates each reference condition against the restored snapshot alone' do
+    HistoryAccess.set(user: nil) do
+      restored = PostVersion.where(post_id: post_record.id, version_no: 3)
+      HistoryAccess.reference_sql('post_versions', 'post_versions').each do |condition|
+        expect(restored.where(Arel.sql(condition)).pluck(:version_no)).to eq([3])
+      end
+      expect(HistoryAccess.visible(PostVersion.where(post_id: post_record.id))
+          .pluck(:version_no)).to eq([3])
+    end
+  end
+
+  it 'keeps every version through a later discard private after another restore' do
+    ['discard', 'restore'].each_with_index do |event, index|
+      PostVersion.create!(post: post_record, version_no: index + 5, event_type: event,
+          title: 'later snapshot', url: post_record.url, tags: '', tags_json: [],
+          parent_post_ids: '', created_at: origin + (index + 5).days)
+    end
+
+    get '/posts/versions', params: { post: post_record.id }
+
+    expect(response).to have_http_status(:ok)
+    expect(response.parsed_body.fetch('versions').pluck('version_no')).to eq([6])
+    expect(response.parsed_body.fetch('count')).to eq(1)
+    expect(response.parsed_body.fetch('versions').first.fetch('title').fetch('prev')).to be_nil
+  end
+
+  ['anonymous', 'member', 'admin'].each do |role|
+    context "as #{ role }" do
+      before do
+        sign_in_as(create(:user, role.to_sym)) unless role == 'anonymous'
+      end
+
+      it 'uses only authorised history timestamps for display' do
+        get '/posts'
+        expect(response).to have_http_status(:ok)
+        row = response.parsed_body.fetch('posts').find { _1.fetch('id') == post_record.id }
+        expected = origin + (role == 'admin' ? 4 : 3).days
+        expect(Time.zone.parse(row.fetch('updated_at'))).to eq(expected)
+      end
+
+      it 'uses the same visibility for date bounds and count' do
+        get '/posts', params: { updated_from: (origin + 4.days).iso8601,
+                                updated_to: (origin + 4.days).iso8601 }
+        expect(response).to have_http_status(:ok)
+        ids = response.parsed_body.fetch('posts').pluck('id')
+        expect(ids).to eq(role == 'admin' ? [post_record.id] : [])
+        expect(response.parsed_body.fetch('count')).to eq(ids.length)
+      end
+
+      it 'sorts using authorised timestamps in both directions' do
+        ['asc', 'desc'].each do |direction|
+          get '/posts', params: { order: "updated_at:#{ direction }" }
+          expect(response).to have_http_status(:ok)
+          expected = role == 'admin' ? [other_post.id, post_record.id] :
+              [post_record.id, other_post.id]
+          expected.reverse! if direction == 'desc'
+          expect(response.parsed_body.fetch('posts').pluck('id')).to eq(expected)
+        end
+      end
+
+      it 'applies authorised timestamp ordering before pagination' do
+        get '/posts', params: { order: 'updated_at:desc', limit: 1 }
+
+        expect(response).to have_http_status(:ok)
+        expected = role == 'admin' ? post_record.id : other_post.id
+        expect(response.parsed_body.fetch('posts').pluck('id')).to eq([expected])
+        expect(response.parsed_body.fetch('count')).to eq(2)
+      end
+
+      it 'counts only visible versions and masks a private previous version' do
+        get '/posts/versions', params: { post: post_record.id }
+        expect(response).to have_http_status(:ok)
+        body = response.parsed_body
+        expected = role == 'admin' ? [4, 3, 2, 1] : [3]
+        expect(body.fetch('count')).to eq(expected.length)
+        expect(body.fetch('versions').pluck('version_no')).to eq(expected)
+        restored = body.fetch('versions').find { _1.fetch('version_no') == 3 }
+        expect(restored.fetch('title').fetch('prev')).to eq(role == 'admin' ? 'version 2' : nil)
+      end
+
+      it 'uses only an authorised previous version for tag filtering' do
+        get '/posts/versions', params: { post: post_record.id, tag: tag.id }
+        expect(response).to have_http_status(:ok)
+        expected = role == 'admin' ? [3, 2, 1] : []
+        expect(response.parsed_body.fetch('versions').pluck('version_no')).to eq(expected)
+        expect(response.parsed_body.fetch('count')).to eq(expected.length)
+      end
+    end
+  end
+end

backend/spec/requests/posts_spec.rb

@@ -629,6 +629,37 @@ RSpec.describe 'Posts API', type: :request do
         create(:post_tag, post: plain_post, tag:, created_at: t3)
       end
 
+      it 'displays history time after pagination without joining history to posts or count' do
+        queries = []
+        subscriber = ->(event) { queries << event.payload.fetch(:sql) }
+        ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+          get '/posts', params: { url: '/version-time/', order: 'url:asc', limit: 1 }
+        end
+
+        expect(response).to have_http_status(:ok)
+        expect(json.fetch('posts').pluck('id')).to eq([history_post.id])
+        expect(Time.zone.parse(json.fetch('posts').first.fetch('updated_at'))).to eq(t2)
+        expect(json.fetch('count')).to eq(3)
+        post_queries = queries.select { _1.include?('FROM `posts`') }
+        expect(post_queries).not_to be_empty
+        expect(post_queries.grep(/post_versions/)).to be_empty
+      end
+
+      it 'omits the history aggregate from count when only sorting by update time' do
+        queries = []
+        subscriber = ->(event) { queries << event.payload.fetch(:sql) }
+        ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+          get '/posts', params: { url: '/version-time/', order: 'updated_at:desc', limit: 1 }
+        end
+
+        expect(response).to have_http_status(:ok)
+        expect(json.fetch('posts').pluck('id')).to eq([newer_post.id])
+        expect(json.fetch('count')).to eq(3)
+        count_queries = queries.select { _1.include?('FROM `posts`') && _1.match?(/COUNT\(/i) }
+        expect(count_queries).not_to be_empty
+        expect(count_queries.grep(/post_versions/)).to be_empty
+      end
+
       ['asc', 'desc'].each do |direction|
         it "sorts by the later of post update and latest version time (#{ direction })" do
           get '/posts', params: { url: '/version-time/', order: "updated_at:#{ direction }" }
@@ -658,6 +689,16 @@ RSpec.describe 'Posts API', type: :request do
         expect(json.fetch('posts').map { |item| item.fetch('id') }).to eq([history_post.id])
         expect(json.fetch('count')).to eq(1)
       end
+
+      it 'counts every timestamp match before pagination' do
+        get '/posts', params: { url: '/version-time/', order: 'updated_at:asc',
+                               updated_from: t1.iso8601, updated_to: t3.iso8601,
+                               limit: 1, page: 2 }
+
+        expect(response).to have_http_status(:ok)
+        expect(json.fetch('posts').pluck('id')).to eq([history_post.id])
+        expect(json.fetch('count')).to eq(3)
+      end
     end
 
     context 'when original_created_from/original_created_to are provided' do

backend/spec/services/counts_export_spec.rb

@@ -221,9 +221,15 @@ RSpec.describe CountsExportDownload::ResponseBody do
       body = described_class.new(source) { |state| states << state; true }
       response = ActionDispatch::Response.new
       response.body = body
-      deferred = response.stream.to_ary
+
+      _, _, rack_body = response.to_a
+
       expect(states).to eq([])
-      expect(deferred.to_a.join).to eq(payload)
+
+      chunks = []
+      rack_body.each { |chunk| chunks << chunk }
+
+      expect(chunks.join).to eq(payload)
       expect(states.count('started')).to eq(1)
     end
   end