Re: Optimizing Bitmap Heap Scan.

On Tue, 8 Dec 2009, niraj patel wrote:
> Thanks very much for the analysis. It does takes 17 sec to execute when
> data is not in cache.

It sounds like the table is already very much ordered by the workspaceid,
otherwise this would have taken much longer.

> What I would like to ask can partitioning around workspaceid would help?
> Or any sort of selective index would help me.

Depends on how many distinct values of workspaceid there are. I would
suggest that given how well ordered your table is, and if you aren't doing
too many writes, then there would be little benefit, and much hassle.

Matthew

--
Now, you would have thought these coefficients would be integers, given that
we're working out integer results. Using a fraction would seem really
stupid. Well, I'm quite willing to be stupid here - in fact, I'm going to
use complex numbers. -- Computer Science Lecturer