Re: SDataSet should handle generated keys

Hello Franck,

Not what I wanted to hear.

The problem is actually deeper.  In particular, if you generate keys 
when records are inserted into the database (as normally done with MS 
SQL) then you need to be able to hold the records without Primary 
Keys.   All very messy, and I was hoping that we would not have to 
deal with it for now.

I think that right way to do it is to enable records to be put in the 
cache with null primary keys.  They can then be updated at commit 
time.  record.Equals(null, null) would be false.  References between 
records in the dataset can be maintained as direct pointers, the 
foreign keys will need to be updated on demand.  I'll make a start.

One alternative for you is to simply pregenerate the ids, and pass 
them to the client.  If they are not needed then just throw them 
away.  That way you do not need to wait for me, although I would like 
you to test the code.

RELATED WORK

Hibernate sort of gets away with null primary keys because objects 
normally only directly reference other object, but bad things happen 
if one has a hashset of children records.

http://msdn.microsoft.com/en-us/library/ks9f57t0.aspx Shows ADO.NET 
has messy solutions.  Give the record a temporary ID, then modify it 
at commit time.

http://www.onjava.com/pub/a/onjava/2006/09/13/dont-let-hibernate-steal-your-identity.html 
suggests using horrible UUIDs as a solution.  (UUID is basically a 
large random number that can be generated in the client and thus 
almost certainly be unique.)

Anthony


At 08:07 AM 11/08/2008, Franck Routier wrote:

>Hi,
>
>I think there is a hole with "records live only in SDataSet" when coming
>to generated primary keys: if we want to create a new record that has a
>generated pkey, we need a way to create a "temporary" generated key.
>
>This would also mean we need to replace this key with the true one when
>the session will begin. Messy.
>This change should also be propagated to referencing records...
>
>Before we didn't have the problem, as records didn't need to have a
>database-like identity until attached. But now they are attached to the
>dataset from the begining...
>
>Any idea on that ?
>
>Franck
>
>

Dr Anthony Berglas, [email protected]       Mobile: +61 4 4838 8874
Just because it is possible to push twigs along the ground with ones nose
does not necessarily mean that is the best way to collect firewood.

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