Re: BUG #17805: Unexpected results when bounds of FOR loop use non-integer numbers

The following bug has been logged on the website:

Bug reference:      17805
Logged by:          Jiangshan Liu
Email address:      jiangshan.liu@tju.edu.cn
PostgreSQL version: 15.2
Operating system:   Ubuntu 18.04
Description:       

I got unexpected results when I ran this PL/pgSQL function:

CREATE FUNCTION test() RETURNS void AS $$
BEGIN
  FOR i IN 1 .. 0.5*5 LOOP
          raise notice '%', i;
        END LOOP;
END;
$$ LANGUAGE plpgsql;
SELECT * FROM test();

The result of the execution is:
NOTICE:  1
NOTICE:  2
NOTICE:  3

I think this result is unexpected because the last round of loop variable is
beyond the specified upper bound of the loop. Is this a bug in a FOR loop?

But this seems to cause incomprehensible results. If it is unsafe to take
values outside the upper and lower bounds of the loop, then this will lead
to unintended consequences.

Is this implicit type conversion necessary? I
think there are two better ways to do it.
One is to report errors directly to the user.