He procedimiento almacenado:

create or replace function make_bi_temporal( _tbl regclass )
returns void as $$
BEGIN
execute format( 'alter table %s drop constraint if exists %s_pkey', _tbl, _tbl );
...

Pero me sale el error cuando se ejecuta select make_bi_temporal( 'check' )

ERROR:  syntax error at or near "_pkey"
LINE 1: alter table "check" drop constraint if exists "check"_pkey

He intentado cambiar de %s a %I:

ERROR:  syntax error at or near "_pkey"
LINE 1: ...ter table "check" drop constraint if exists """check"""_pkey

a %L:

ERROR:  syntax error at or near "'"check"'"
LINE 1: alter table "check" drop constraint if exists '"check"'_pkey

Quiero check_pkey.

Cómo formatear sin comillas?