Re: Re: sampling.c and potential divisions by 0 ang log(0) with tablesample and ANALYZE in 9.5 - Mailing list pgsql-bugs

I wrote:
> Petr Jelinek <petr@2ndquadrant.com> writes:
>> On 2015-06-25 10:01, Michael Paquier wrote:
>>> I think that we should change the returned double to be (0.0,1.0]

>> Agreed.

> I find this to be a pretty bad idea.  That definition is simply weird;
> where else in the world will you find a random number generator that does
> that?  What are the odds that any callers are actually designed for that
> behavior?

And, in fact, a bit of looking quickly finds a counterexample, in
analyze.c:

            int     k = (int) (targrows * sampler_random_fract(rstate.randstate));

            Assert(k >= 0 && k < targrows);

You can't just whack this around to satisfy some new call sites without
considering the behavior of existing use-cases.

            regards, tom lane