Re: BUG #13453: PostgreSQL 9.5dev pgbench exponential distribution bug? (when threshold is small)

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: digoal(at)126(dot)com, PostgreSQL Bugs List <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: BUG #13453: PostgreSQL 9.5dev pgbench exponential distribution bug? (when threshold is small)
Date: 2015-06-18 15:32:21
Message-ID: 20150618153221.GG133018@postgresql.org
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Fabien COELHO wrote:
>
> Hello,
>
> >\setrandom id 1 50000 exponential 0.0000001
> >insert into test values (:id);
>
> Yes, a very small coefficient on a truncated exponential is pretty close to
> a uniform distribution. I think that this is a mathematical fact, not a bug.

It's a fact of life also ... you don't notice exponentially-growing
stuff until it's way out of hand :-)

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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