Re: [PATCH] Custom code int(32|64) => text conversions out of performance reasons

Greg Stark <gsstark(at)mit(dot)edu> writes:
> On Sat, Nov 20, 2010 at 6:31 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>> I had given some thought to whether it might make sense to try to
>>> figure out how long the string will be before we actually start
>>> generating it, so that we can just start in the exactly right space
>>> and have to clean up afterward. But the obvious implementation seems
>>> like it could be more expensive than just doing the copy.

>> Yeah. You certainly don't want to do the division sequence twice,
>> and a log() call wouldn't be cheap either, and there don't seem to
>> be many other alternatives.

> There are bittwiddling hacks for computing log based 2. I'm not sure
> it's worth worrying about to this degree though.

I think converting log2 to log10 *exactly* would end up being not so
cheap, anyhow.

regards, tom lane