Re: Hashes from composite keys?

Daniel Pitts wrote:

> On 7/26/2010 4:03 PM, Bob Badour wrote:
>

>> Daniel Pitts wrote:
>>
>>> On 7/23/2010 1:14 PM, Karsten Wutzke wrote:
>>>
>>>> Hello,
>>>>
>>>> what are the best practices for generating hash codes from composite
>>>> keys? I need to mimic something like what a composite index does. In
>>>> fact, it's for mapping between relational keys and object IDs.
>>>>
>>>> Can anyone point me into the right direction please?
>>>
>>> Yes, don't use Hashing, but use a composite key. Aggregate the keys
>>> into one value (eg, the BIT pattern of that one key value is the
>>> concatination of the bit patterns of all the other values.)
>>
>> That's rather dumb advice.

Yes, really.

> The OP said "I need to mimic something like what a composite
> index does" Well, I suggested a simplified (yet correct) version of
> what a composite index does.

Your advice assumes it makes any sense to "do what a composite index does" to "map between relational keys and object IDs". That's a dumb assumption making your advice dumb advice. Received on Tue Jul 27 2010 - 02:47:25 CEST