Revert "fix(tag): prevent dupl. tags on concurrent inserts (mastodon#35792)"

This reverts commit ccd5542.

Author: hina

app/models/tag.rb

@@ -90,17 +90,8 @@ def history
 
   class << self
     def find_or_create_by_names(name_or_names)
-      names = Array(name_or_names).map { |str| [normalize(str), str] }.uniq(&:first)
-
-      names.map do |(normalized_name, display_name)|
-        tag = begin
-          matching_name(normalized_name).first || create!(
-            name: normalized_name,
-            display_name: display_name.gsub(HASHTAG_INVALID_CHARS_RE, '')
-          )
-        rescue ActiveRecord::RecordNotUnique
-          find_normalized(normalized_name)
-        end
+      Array(name_or_names).map(&method(:normalize)).uniq { |str| str.mb_chars.downcase.to_s }.map do |normalized_name|
+        tag = matching_name(normalized_name).first || create(name: normalized_name)
 
         yield tag if block_given?
 

spec/models/tag_spec.rb

@@ -134,27 +134,6 @@
     end
   end
 
-  describe '.find_or_create_by_names_race_condition' do
-    it 'handles simultaneous inserts of the same tag in different cases without error' do
-      tag_name_upper = 'Rails'
-      tag_name_lower = 'rails'
-
-      threads = []
-
-      2.times do |i|
-        threads << Thread.new do
-          described_class.find_or_create_by_names(i.zero? ? tag_name_upper : tag_name_lower)
-        end
-      end
-
-      threads.each(&:join)
-
-      tags = described_class.where('lower(name) = ?', tag_name_lower.downcase)
-      expect(tags.count).to eq(1)
-      expect(tags.first.name.downcase).to eq(tag_name_lower.downcase)
-    end
-  end
-
   describe '.search_for' do
     it 'finds tag records with matching names' do
       tag = Fabricate(:tag, name: "match")