Is a bitmap index the best choice for a range query?

Question

I'm trying to choose between these query plans for a range query:

• Sequential table scan
• Bitmap index
• B+ tree index
• Hash index

My instinct is that a bitmap index would work here based on what I've read. Does that sound right?

Answer 1

This link has a pretty good explanation: http://dylanwan.wordpress.com/2008/02/01/bitmap-index-when-to-use-it/

And of course wikipedia: http://en.wikipedia.org/wiki/Bitmap_index

In short, it depends on the percentage of unique values to the total number of rows. If you have only a few unique values, the bitmap index is probably the way to go.