Hi Folks,
The UUIDLib library which I (had) wrote uses the original method of
guid generation, and produces a reversed shrunken version (22 chars
all of which are url friendly), so the index prefix compression works ok.

Regards
Ian Newby

--- In Firebird-Architect@yahoogroups.com, Kevin Berry
<kevinbe71@y...> wrote:

> Thanks Ann. Nice theory but....
>
> Here are two serial GUIDs (i.e. produced a split
> second apart from one another on my system):
>
> 255DAB3A-E481-4F8B-BE8A-EEB079DA9101
> 63ECDA6A-4906-4F54-8F54-D6C73386E989
>
> Try to spot the bits they have in common. ;-)
>
> Microsoft started out by making GUIDs serial but....
> as the Melissa author discovered... this allowed
> people to determine which machine produced the GUIDs.
> See reference below (section titled "Algorithm"):
>
> http://en.wikipedia.org/wiki/GUID
>
> Of course, if you're using some other algorithm that
> is not the Microsoft one then I guess this could still
> hold true. However, I like to assign a GUID by a
> system call and using the value in my objects
> directly... rather than waiting for the database to
> assign one and then having to retrieve it from some
> output var. This has the added benefit of objects in
> memory having unique IDs even if they haven't been
> stored in the database yet.
>
> Cheers,
> Kevin.
>
> --- "Ann W. Harrison" <aharrison@i...> wrote:
> > > "reversed GUID" sounds like something you
> > > made up?
> >
> > A GUID is a string of bytes that is "guaranteed" to
> > be unique. It
> > starts with a counter and adds factors that are
> > constant for a
> > particular computer. Firebird uses prefix
> > compression on its indexes,
> > so having the constant part first reduces the size
> > of indexes by a lot.
> >
> > Regards,
> > Ann
>
>
>
>
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