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Krunal,
1) you can try "select for update" when you get
your max() + 1 . That will lock the record until your transaction
commits.
The plus is you won't have duplicate values. The
minus is your transactions will be serialized.
2) i assume you are not using entity beans
otherwise I'd suggest a sequence blocks pattern described chapter 5 of "EJB
Design Patterns" by Floyd Marinescu (available free in PDF format of www.the
serverside.com) so create another session bean, inside the bean start another
transaction, retrieve/update the key within that transaction. It will be be very
short all it should is read and up[date the key value and return
it.
If you have just one server and not a cluster, the
easiest solution would be to read the index on start up and bind it inside a
class into JNDI tree where the class would look like this
public class IndexCounter{
private int index;
...
public int
getIndex(){
return
index++;
}
}
You even don't have to synchronize the getter for
it's impossible to get a duplicate in this case.
----- Original Message -----
Sent: Thursday, May 30, 2002 4:07
AM
Subject: [jdjlist] HELP REQUIRED :
COMPLEX TRANSACTIONS
Dear
All,
I am using
ejb (statelss session bean), and using bean managed transaction
processing.
I have one method which includes inserts
in one table (min. 8 rows) and then select
statements and one select includes
max() +1 value of one column from table, using that
value makes insert into one table say 'A'.
finally at the end of method, commiting the transaction.
The database data for table 'A' is becoming inconsistent as many
users are firing the same method
and 2 or 3 users get
same max+1 value as insert is done for that value.
I can not create a sequence due to some business function
limitation.
One solution
that we are thinking of is :
On server, create one class, having sync.
get and set methods using one flag and in ejb
check that flag and then get max+1 value
in order to control max+1 value conflict.
Is this
solution right ?
Please mail
me the solutions that u all can provide me as soon as possible on JDJ
List.
Thanks & Regards,
Krunal Shimpi.
Passenger Solutions
Group,
Airlines division,
Kale Consultants Ltd.
Tel : 8259580 - 89 Extn : 322
http://www.kaleconsultants.com
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