CREATE FUNCTION 
	contractor_before_insert() returns opaque AS $$
		begin
			INSERT INTO document DEFAULT VALUES;
			new.document_id = currval('document_document_id_seq');
			RETURN new;
		end;
$$ LANGUAGE plpgsql;

CREATE FUNCTION 
	contractor_before_insert() returns opaque AS $$
		begin
			IF (new.document_id не определена) then
				INSERT INTO document DEFAULT VALUES;
				new.document_id = currval('document_document_id_seq');
				RETURN new;
			end;
		end;
$$ LANGUAGE plpgsql;