Re: plans for bitmap indexes?

On Tue, 19 Oct 2004, Sailesh Krishnamurthy wrote:

> >>>>> "Tom" == Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>
> Tom> One huge advantage is that the actual heap visiting becomes
> Tom> efficient, eg you never visit the same page more than once.
> Tom> (What you lose is the ability to retrieve data in index
> Tom> order, so this isn't a replacement for existing indexscan
> Tom> methods, just another plan type to consider.)
>
> Even without bitmap indexes, without trying to use multiple indexes
> etc. this (visiting a page only once) is useful.
>
> In other words, I'd like to see the indexscan broken up into: (1) an
> operator that returns a list of TIDs, (2) Sort the TIDs and (3) an
> operator that fetches heap tuples from the sorted TID list.

I'm uncertain about the potential benefit of this. Isn't/shouldn't the
effects of caching be assisting us here?

Gavin