| From: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Raúl Marín Rodríguez <rmrodriguez(at)carto(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 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: | 2017-12-06 05:58:00 |
| Message-ID: | alpine.DEB.2.20.1712060647280.19178@lancre |
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| Thread: | |
| Lists: | pgsql-hackers |
>> In both cases we'd return a double but we use the fast ipow if it's
>> possible (which can be 20x faster), so at the cost of an extra cast if
>> you need an int, we'd have a consistent API. Would this be acceptable?
>
> It seems OK to me.
Computing as an int, casting to double and back to int8 can generate a
loss of precision. However for powers of 2 it works exactly, so eg
computing a mask it would be ok.
This proposal does not exactly match SQL behavior, but I do not see this
as a problem, which is why I was happy with the previous proposal.
--
Fabien.
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