From: Lars-Erik Bjørk
Date: January 21 2009 4:44pm
Subject: Re: search for null values in indexed columns
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Vlad,

I have been looking at something related today,  http://bugs.mysql.com/bug.php?id=42208
I will look more at this tomorrow ... Interesting!



On Jan 21, 2009, at 4:28 PM, Vladislav Vaintroub wrote:

> 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.
>
>
>
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