Re: BUG #14737: Wrong PL/pgSQL behaviour

On Fri, Jul 7, 2017 at 9:10 AM, <frank(dot)von(dot)postgresql(dot)org(at)familie-gard(dot)de>
wrote:

> Bug reference: 14737
> Logged by: Frank Gard
> Email address: frank(dot)von(dot)postgresql(dot)org(at)familie-gard(dot)de
> PostgreSQL version: 9.6.3
> Operating system: Debian GNU/Linux
>

​Not a bug - RANDOM() is a volatile function so it gets evaluated once per
row.

UPDATE ttb_histogramm
> SET
> anzahl = anzahl + 1
> WHERE
> wert = p_von + FLOOR( ( 1 + p_bis - p_von ) * RANDOM() )

Unfortunately this is not the case. When calling it
> multiple times, it returns numbers smaller and greater, and always
> different
> values for each call. Very strange (to me)!!!
>

​Which is the symptom one will see if, for every row, the value of random
is different.
​

> When I change my function a little bit, writing the random number into an
> INTEGER variable, and using this variable within my UPDATE statement,
> everything works fine:
>

​Then this is what you should do.

​David J.