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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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Thread
Problems with record visibility and how it is computedOlav Sandstaa21 Jan
  • search for null values in indexed columnsVladislav Vaintroub21 Jan
    • Re: search for null values in indexed columnsLars-Erik Bjørk21 Jan
    • Re: search for null values in indexed columnsKevin Lewis21 Jan
      • RE: search for null values in indexed columnsVladislav Vaintroub21 Jan
        • Re: search for null values in indexed columnsKevin Lewis21 Jan
      • Re: search for null values in indexed columnsJames Day23 Jan
  • Re: Problems with record visibility and how it is computedOlav Sandstaa23 Jan
    • Re: Problems with record visibility and how it is computedJim Starkey23 Jan
      • Re: Problems with record visibility and how it is computedKevin Lewis28 Jan
        • Re: Problems with record visibility and how it is computedJim Starkey28 Jan
          • Re: Problems with record visibility and how it is computedKevin Lewis28 Jan
            • Cycle Locking (was Problems with record visibility and how it iscomputed)Jim Starkey28 Jan
            • Re: Problems with record visibility and how it is computedAnn W. Harrison28 Jan
              • Re: Problems with record visibility and how it is computedJim Starkey28 Jan
                • Re: Problems with record visibility and how it is computedAnn W. Harrison28 Jan
                  • Re: Problems with record visibility and how it is computedOlav Sandstaa26 Feb
                    • New Transaction State object (Was: Problems with record visibility andhow it is computed)Olav Sandstaa16 Mar
                      • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Kevin Lewis16 Mar
                      • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Jim Starkey16 Mar
                        • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Olav Sandstaa19 Mar
                          • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Jim Starkey19 Mar
                            • RE: New Transaction State object (Was: Problems with record visibilityand how it is computed)Vladislav Vaintroub20 Mar
                            • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Olav Sandstaa20 Mar
                              • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Jim Starkey20 Mar
          • Re: Problems with record visibility and how it is computedOlav Sandstaa28 Jan
            • Re: Problems with record visibility and how it is computedJim Starkey28 Jan
              • Another Idea for Transaction Lifetime ControlJim Starkey28 Jan
                • Re: Another Idea for Transaction Lifetime ControlJim Starkey29 Jan
              • RE: Problems with record visibility and how it is computedXuekun Hu4 Feb
          • Re: Problems with record visibility and how it is computedAnn W. Harrison28 Jan
  • Quick question on row countsKeith Murphy24 Jan
    • Re: Quick question on row countsJim Starkey25 Jan
      • Re: Quick question on row countsKeith Murphy25 Jan