Re: five-key syscaches

On Wed, Jul 14, 2010 at 10:56 AM, Yeb Havinga <yebhavinga(at)gmail(dot)com> wrote:
> Robert Haas wrote:
>> On Wed, Jul 14, 2010 at 7:27 AM, Yeb Havinga <yebhavinga(at)gmail(dot)com> wrote:
>>> Attach is a new patch with all things described above addressed.
>> Thanks!
>>
>> I think we should probably hold off applying this until some of the
>> other KNNGIST work is ready, or we have some other concrete need for
>> 5-key syscaches.
>
> Any thoughts about the << 16 and >> 16 bit shifting on the 5th hash key
> computation? I blithely copied it from the 3rd key.

Hmm, I thought I had the bit in my version, but I see that I don't.
Must have gotten lost from an earlier incarnation. It's probably bad
to duplicate the bit-shifting pattern of an existing key. We might
want to shift by something that's not a multiple of 8, like 12/20.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company