BITMAP MERGE vs BITMAP OR

This question is in reference to operations that you may encounter when doing an EXPLAIN PLAN. I'm trying to understand the difference between the BITMAP MERGE and a BITMAP OR operations.

Here's what the manual says about BITMAP MERGE:

	Merges several bitmaps resulting from a
	range scan into one bitmap

Here's what the manual says about BITMAP OR:

        computes the bitwise OR of two bitmaps

To me, it seems as if the manual is saying the same thing in two different ways. When ORing two bitmaps, I would expect to get back rows that appear in either bitmap. When merging two bitmaps, I would also expect the same thing. So what's the difference?

Jonathan Received on Sun Aug 30 1998 - 12:15:19 CDT