def up
ActiveRecord::Base.connection.execute 'CREATE INDEX index_links_on_substring_head_uuid on links (substring(head_uuid, 7, 5))'
ActiveRecord::Base.connection.execute 'CREATE INDEX index_links_on_substring_tail_uuid on links (substring(tail_uuid, 7, 5))'
def up
ActiveRecord::Base.connection.execute 'CREATE INDEX index_links_on_substring_head_uuid on links (substring(head_uuid, 7, 5))'
ActiveRecord::Base.connection.execute 'CREATE INDEX index_links_on_substring_tail_uuid on links (substring(tail_uuid, 7, 5))'