[Bizgres-general] Re: Non equality operators and bitmap indexes (was : A bitmap index access method is available...)

[Mark Kirkwood]

Simon Riggs wrote:
> On Wed, 2005-12-28 at 23:02 -0800, Jie Zhang wrote:
> 
> 
>>There are three known encoding schemes for the bitmap index: the equality
>>scheme (each bitmap is associated with each one of all distinct values), the
>>interval scheme (each bitmap is associated with several distinct values that
>>lie within an interval), and the range scheme (each bitmap is associated
>>with distinct values that are less/greater than a given value). Each of
>>these schemes has different performance advantages for different queries.
>>Currently, we only support the equality scheme. I think that the better way
>>is to let users decide which encoding scheme to use. Any comments on this?
> 
> 
> You should be able to do as Mark suggests, irrespective of the coding
> scheme used. (More work....)
> 

Exactly - range encoding makes it *easier* to do non equality 
comparisons, but you certainly can do 'em with equality encoding too (it 
does take more bitmap operations as I understand it). I have been reading:

http://www.cs.brown.edu/courses/cs227/Papers/Indexing/ioannidis98.pdf

which seems to cover this stuff quite well!


Best wishes for 2006

Mark