| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Raúl Marín Rodríguez <rmrodriguez(at)carto(dot)com> |
| Cc: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] pow support for pgbench |
| Date: | 2017-12-26 19:29:03 |
| Message-ID: | CA+TgmoY_ywv1zXi_2cOCB7rmvTSweqdHbN+5jj+hjGHLaJZmpA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Dec 22, 2017 at 12:46 AM, Raúl Marín Rodríguez
<rmrodriguez(at)carto(dot)com> wrote:
>> 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.
This version looks good to me, except that I wonder if we should try
to switch to the floating-point version if the integer version
would/does overflow.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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