search for null values in indexed columns

[Vladislav Vaintroub]

Hi,
I'm quite intrigued by this place in StorageDatabase::makeKey (this one
translates MySQL key values to Falcon key values during the search).

It appears that we stop building a key when encountering a null value and
ignore all following ranges
	
Foreach key segment
	if (nullFlag)
		{
		<blah>		
		break;
		}
Endforeach

That is, when NULL is given in the first segment, we produce zero-length
Falcon key
So how does searching for NULL works in practice?

How does search  range search in multisegment indexes
lower bound (a = NULL, b = const1) 
upper bound (a = NULL ,b = const2) 

is supposed to work?

Thanks for the answer!

My first suspicion is that NULLs are excluded because NULL is encoded the
same as numeric 0 (0x80 in index) and this lead to wrong answer. But I'd
prefer to hear a qualified answer on how it was originally designed and
supposed to work.