[Lazarus] Postgres database again...

[Michael Van Canneyt]

On Wed, 28 May 2008, Graeme Geldenhuys wrote:

> 2008/5/28 Graeme Geldenhuys <graemeg.lists at gmail.com>:
> > 2008/5/28 Bogusław Brandys <brandys at o2.pl>:
> >> "straight GUIDs (e.g. generated by Delphi written application) has their
> >> significant part at the end which does not provide for optimal indexing. Use
> >> of the UDF generating UUID (reverse GUID) is said to improve performance
> >> over the PK dramatically.
> >
> > I'll try and find the code for the 'UDF generating UUID (reverse
> > GUID)' and create a tiOPF OID generator for it.
> 
> Under Linux, it seems FPC gets the kernels UUID when you ask to create
> a GUID via CreateGUID().  Plus the GUID/UUID returned is totally
> random, to parts are the same as the previous request.
> 
> eg;
> 
> graemeg at graemeg:~$ cat /proc/sys/kernel/random/uuid
> ca65c9ce-b097-4ff0-8a1a-7f41628e9982
> graemeg at graemeg:~$ cat /proc/sys/kernel/random/uuid
> c29650af-5562-4669-967d-5227402c0252
> graemeg at graemeg:~$ cat /proc/sys/kernel/random/uuid
> f757c538-70eb-4432-b094-dc3ad5b824f5
> graemeg at graemeg:~$ cat /proc/sys/kernel/random/uuid
> 4a8dca85-2040-4fe5-afa2-dfeb5066c731
> graemeg at graemeg:~$ cat /proc/sys/kernel/random/uuid
> e576429b-fdf9-485a-b9f5-3319a2067b24
> graemeg at graemeg:~$ cat /proc/sys/kernel/random/uuid
> f7335eb4-26bc-4467-8d99-04a3ef8702fd
> 
> 
> So I can't see the point in reversing the returned string.  Maybe
> Delphi or Windows works different and some parts are the same as the
> previous request.

Yes:

The MAC address of the network card was used as part of the GUID
(because normally the MAC address is unique). However, this was 
discovered to be 'traceable', so maybe the windows implementation 
has changed meanwhile.

Michael.