zammad/config/initializers/db_preferences.rb

case ActiveRecord::Base.connection_config[:adapter]
when 'mysql2'
  Rails.application.config.db_4bytes_utf8 = false
  Rails.application.config.db_case_sensitive = false
  Rails.application.config.db_like = 'LIKE'
  Rails.application.config.db_null_byte = true
when 'postgresql'
  Rails.application.config.db_4bytes_utf8 = true
  Rails.application.config.db_case_sensitive = true
  Rails.application.config.db_like = 'ILIKE'
  Rails.application.config.db_null_byte = false
end