[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?
> 
> 

Notwithstanding the comments in Simon's and my previous mails, Jie's 
suggestion of exposing the encoding type as a choice is certainly worth 
doing in my view.

For instance, if you know that you are mostly using range predicates in 
your queries, then it makes sense to choose range (or interval) 
encoding, conversely if you are mainly using equality predicates, then 
equality encoding would be the one to pick!

Syntactically, something like the 'pattern_ops' choices for btree 
indexes might be pretty painless.


Cheers

Mark