Debería poder consultar la tabla pg_class para ver si existe el relname.
IF EXISTS (SELECT 0 FROM pg_class where relname = '<my sequence name here>' )
THEN
--stuff here
END IF;
Debería poder consultar la tabla pg_class para ver si existe el relname.
IF EXISTS (SELECT 0 FROM pg_class where relname = '<my sequence name here>' )
THEN
--stuff here
END IF;