> > The most nearly comparable thing is be the notion of "partial
> > indexes," where, supposing you had 60 region codes (e.g. - 50 US
> > states, 10 Canadian provinces), you might set up indices thus:
> For example, imagine you have a table on a dating website with 18 columns
> representing 18 different characteristics for matching. Imagine that you
> index each of those columns seperately. If you do:
>
> SELECT * FROM people WHERE orientation = 'gay' AND gender = 'male' AND city =
> 'San Francisco';
I think bitmap indexes do have valid use cases, but partitioned indexes
are really a wonderful feature with a lot of use cases, maybe including this one.
Workable examples for useful partitioned indexes, that help here are:
create index people_male_ix on people (city) where gender = 'male';
create index people_gay_ix on people (city) where orientation = 'gay';
create index people_male_gay_ix on people (city) where gender = 'male' and orientation = 'gay';
Note, that the indexed column differs from the partitioning clause.
Note also, that the last index will perform way better than a combo of bitmap indexes.
Andreas