Re: Single client performance on trivial SELECTs

On Thu, Apr 14, 2011 at 4:10 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
>> On Thu, Apr 14, 2011 at 11:15:00AM -0700, Robert Haas wrote:
>>> It shouldn't be
>>> terribly difficult to come up with some kind of hash function based
>>> on, say, the first two characters of the keyword that would be a lot
>>> faster than what we're doing now.
>
>> I'd look at `gperf', which generates code for this from your keyword list.
>
> FWIW, mysql used to use gperf for this purpose, but they've abandoned it
> in favor of some homegrown hashing scheme.  I don't know exactly why,
> but I wonder if it was for licensing reasons.  gperf itself is GPL, and
> I don't see any disclaimer in the docs saying that its output isn't.

I dont think it matters -- see the entry in the bison faq:
"Is there some way that I can GPL the output people get from use of my
program? For example, if my program is used to develop hardware
designs, can I require that these designs must be free?

In general this is legally impossible; copyright law does not give
you any say in the use of the output people make from their data using
your program. If the user uses your program to enter or convert his
own data, the copyright on the output belongs to him, not you. More
generally, when a program translates its input into some other form,
the copyright status of the output inherits that of the input it was
generated from."

merlin