[innagadadavida]

One option when your DB doesn't have those primitives is to convert the bits to word 011 -> "unsetbit2 setbit1 setbit0" then treat that column to have a text index - this is equivalent to doing hamming distance search. I did this with MySQL for 20M gifs for near duplicate detection and it worked very well.

[willcodeforfoo]

Interesting idea, I'll have to give this a shot!