On 11/06/2011 12:25 PM, Thomas Mueller wrote:
Hi,
Okay. How do you generate the same sequence id for different triggers in
the same transaction (and different ids for different transactions)?
The first operation in the transaction could generate a new sequence
id, and all other operations could then use the last value of the
generated sequence: http://h2database.com/html/functions.html#currval
I guess this is how I would solve the problem. It is relatively
database independent.
Regards,
Thomas
Hi Thomas,
I need help understanding your proposal. Looking at
http://h2database.com/html/functions.html#currval
1. Does "session" refer to a database connection?
2. I am concerned about the part of the description that reads
"independent of the session". Doesn't this mean that if two connections
run concurrently CURRVAL() may lead to race-conditions?
3. I'm trying to use transaction IDs in database triggers. I have no way
of knowing which one runs first, as such I don't know when to run
NEXTVAL() and when to run CURRVAL(). Any suggestions?
4. Assuming we get this working, why did you decide to implement
TRANSACTION_ID() in terms of a UUID string instead of this approach? The
only benefit I can think of is cross-database uniqueness, but for single
databases it seems the performance would be worse...?
Thanks,
Gili
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