Re: [HACKERS] [WIP] Zipfian distribution in pgbench

Hello,

>> Is this bias expected from the drawing method, say because it is 
>> approximated and the approximation is weak at some points, or is there 
>> an issue with its implementation, says some shift which gets smoothed 
>> down for higher indexes?
>
> I have checked paper where such implementation was proposed and there 
> theta allowed only on range between 0 and 1. It seems like it is not 
> guaranteed that it should work well when theta is more than 1.

Ok.

I see a significant issue with having a random_zipfian function which does 
not really return a zipfian distribution under some parameter values. If 
there is no better alternative, I would suggest to restrict the parameter 
for values between 0 and 1, or to find a better approximation for theta >= 
0.

> I am attaching paper, see page 23.

Thanks for the paper. It reminds me that I intended to propose a 
parametric pseudo-random permutation for pgbench, some day.

-- 
Fabien.