Re: The age-old database design question - Integers or GUID/UUID for primary keys ? What are your thoughts ?

My understanding is that Db2i uses CMPSWP "under the covers" to implement the "IDENTITY" capability.

Just saying ...

On Monday, December 14, 2020, 5:33:44 PM EST, Peter Dow <petercdow@xxxxxxxxx> wrote:

Hi James,

Yes, and correctly done application-wide, you theoretically shouldn't
need to pre-check for existence or worry about duplicates when writing. 
And since this about design, presumably of a new application, that makes
sense.

Tim Father's suggestion of CMPSWP is interesting -- I'd never heard of
that. Sounds like a good basis for an identifier factory.

--
*Peter Dow* /
Dow Software Services, Inc.
909 793-9050
petercdow@xxxxxxxxx <mailto:petercdow@xxxxxxxxx>
pdow@xxxxxxxxxxxxxx <mailto:pdow@xxxxxxxxxxxxxx>

/

On 12/14/2020 1:14 PM, James H. H. Lampert wrote:

On 12/14/20 10:37 AM, Peter Dow wrote:

Pre-checking for existence doesn't always work. If you have a bunch
of jobs adding to the file at the same time, there's a pretty good
chance that between the time you pre-check and when you write the
record, that some other job may beat you to the write.

So have your identifier factory set up in such a way that calling it
puts an exclusive lock on something, that the calling program then has
to explicitly release once the new record has been written.

--
JHHL