Performance issues when adding or updating tags

[bduran82]

Running on Rails 4.2.8 and gem version 5.0.0 we experience a poor performance when updating the tags of a model with big number of tags.

In our project we need to handle models with sometimes big number of tags (up to around 300). We have experienced performance issues in our database when updating tags in those models that even led to request timeouts. The source seems to be the huge amount of database queries like the following:

SELECT `tags`.* FROM `tags` WHERE (name = BINARY 'editor' OR name = BINARY 'funding' OR name = BINARY 'transfers' OR name = BINARY 'role' OR name = BINARY 'editorial' OR ...

It looks like in ActsAsTaggableOn::Tag find_or_create_all_with_like_by_name all the tags attached to the model are repeatedly reloaded for every tag to avoid collisions in the database. Shouldn't the tags be loaded once in the beginning of the method and then only refreshed again in case there is a collision?

  def self.find_or_create_all_with_like_by_name(*list)
      list = Array(list).flatten

      return [] if list.empty?

      list.map do |tag_name|
        begin
          tries ||= 3

          existing_tags = named_any(list)
          comparable_tag_name = comparable_name(tag_name)
          existing_tag = existing_tags.find { |tag| comparable_name(tag.name) == comparable_tag_name }
          existing_tag || create(name: tag_name)
        rescue ActiveRecord::RecordNotUnique
          if (tries -= 1).positive?
            ActiveRecord::Base.connection.execute 'ROLLBACK'
            retry
          end

          raise DuplicateTagError.new("'#{tag_name}' has already been taken")
        end
      end
    end