Re: Patch for bug#42208

[Jim Starkey]

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.

-- 
Jim Starkey
President, NimbusDB, Inc.
978 526-1376