Alex Turner <armtuk@gmail.com> writes:
> I was wondering about index types. Oracle has an index type called a
> 'bitmap' index.
There's a great deal about this in the list archives (probably more in
pgsql-hackers than in -performance). Most of the current interest has
to do with building in-memory bitmaps on the fly, as a way of decoupling
index and heap scan processing. Which is not quite what you're talking
about but should be pretty effective for low-cardinality cases. In
particular it'd allow AND and OR combination of multiple indexes, which
we do poorly or not at all at the moment.
regards, tom lane