1、使用postgre账号进入到相应的模式下执行：

CREATE OR REPLACE FUNCTION boolean_to_smallint(b boolean) RETURNS smallint AS $$
    BEGIN
            RETURN (b::boolean)::bool::int;
    END;
$$LANGUAGE plpgsql;

CREATE CAST (boolean AS smallint) WITH FUNCTION boolean_to_smallint(boolean) AS implicit;

2、测试：（is_leader字段为smallint类型）

UPDATE public."user"
        SET is_leader=True
        WHERE id='125';

参考
[1] http://www.voidcn.com/article/p-exdbkvab-bve.html
[2] https://github.com/digoal/blog/blob/master/201710/20171013_03.md
[3] https://blog.csdn.net/weixin_33816300/article/details/90001704