Re: Patch for bug#42208

[MARK CALLAGHAN]

On Mon, Feb 16, 2009 at 1:46 PM, Jim Starkey <jstarkey@stripped> wrote:
> Vladislav Vaintroub wrote:
>>
>> Hi Lars-Erik,
>> I wonder if adding 0x00 to the (binary) string values that already start
>> with 0x00 would not be less works that modifying index walker etc. This
>> looks like huge amount of work you have done (good) but I wonder if there
>> is
>> a good reason for it. Assuming (binary) strings that start with 0x00 are
>> really seldom, prepending 0x00 to a key after a check is not going to be
>> an
>> expensive operation. And that makes NULL *really* different from other
>> index
>> values. And that allows maybe in some distant future index-only access, so
>> you can answer "is null/is not null" without extra accessing the record
>> and
>> this is a real performance advantage.
>>
>>
>
> Why do you want to do that?  Is the following sufficient:
>
>  1. A null is represented as either a zero length key or a missing
>     segment in a multi-segment key.  This collates lowest.
>  2. A zero length binary key is represented by a single byte of zero.
>  3. A binary key with a single zero byte is indistinquishable from a
>     zero length (but non-null) key
>  4. A binary key with a leading zero byte and a subsequent non-zero
>     byte will collate about #2 and #3.
>
> I don't think we really care about the ordering of a non-null, zero length
> key and and all zero binary key.  I don't think anyone else should, either.

Oracle cared less than you want Falcon to care. Not everyone was happy
about that.
http://www.google.com/search?q=wtf+oracle+null+empty+string

>
> --
> Jim Starkey
> President, NimbusDB, Inc.
> 978 526-1376
>
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-- 
Mark Callaghan
mdcallag@stripped