Re: [HACKERS] pow support for pgbench

Hi Fabien,

Thanks for the review.

If a double is always returned, I'm wondering whether keeping the ipow
> version makes much sense: In case of double loss of precision, the
> precision is lost, too bad, and casting back to int won't bring it back.

I've kept it because knowing that both are ints enables not making a lot of
checks (done in math.h pow) so it's way faster. In my system it's 2-3ns vs
~40ns. I'm willing to settle for using just pow() if that makes it clearer.

In the doc, I'm not sure that "Numeric" brings anything. "Exponentiation"
> would be enough.

Done.

Also, in pg I just noticed that POW is a shorthand for POWER. Maybe both
> should be supported? Or not.

I've never used power instead of pow, but I've added for compatibility
shake.

Attached the updated patch.

On Thu, Dec 21, 2017 at 10:48 PM, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> wrote:

>
> Hello Raúl,
>
> v7 needs a rebase.
>>>
>>> Also, you might try to produce a version which is compatible with
>>> Robert's
>>> constraints.
>>>
>>
> My 0.02€ on this new version: Applies cleanly, compiles and works.
>
> I cannot say that I like it more than the previous version.
>
> If a double is always returned, I'm wondering whether keeping the ipow
> version makes much sense: In case of double loss of precision, the
> precision is lost, too bad, and casting back to int won't bring it back.
>
> In the doc, I'm not sure that "Numeric" brings anything. "Exponentiation"
> would be enough.
>
> Also, in pg I just noticed that POW is a shorthand for POWER. Maybe both
> should be supported? Or not.
>
> --
> Fabien.

--

*Raúl Marín Rodríguez *carto.com