Re: index structure for 114-dimension vector

Jeff Davis wrote:
> On Fri, 2007-04-20 at 12:07 -0700, Andrew Lazarus wrote:
>> I have a table with 2.5 million real[] arrays. (They are points in a
>> time series.) Given a new array X, I'd like to find, say, the 25
>> closest to X in some sense--for simplification, let's just say in the
>> usual vector norm. Speed is critical here, and everything I have tried
>> has been too slow.
>>
>> I imported the cube contrib package, and I tried creating an index on
>> a cube of the last 6 elements, which are the most important. Then I
>
> Have you tried just making normal indexes on each of the last 6 elements
> and see if postgresql will use a BitmapAnd to combine them?
>
>

I don't think that will work for the vector norm i.e:

|x - y| = sqrt(sum over j ((x[j] - y[j])^2))


Cheers

Mark