Rick Hillegas-3 wrote > 1) Something about the problem description is not clear. The first > tooMuchContention exception occurs within a half minute of booting the > database. It is very hard to understand how your application could chew > through 2 billion sequence numbers in that short time period. Perhaps > your identity column has already leaked its entire range due to setting > derby.language.sequence.preallocator to a high number and then crashing > without bringing the database down gracefully.
application is under stress test. Rick Hillegas-3 wrote > 2) From the stack traces, it appears that you are using Hibernate. Under > the covers, Hibernate calls a JDBC method which Derby does not support > but which, unfortunately, Derby does not reject either > (Statement.getGeneratedKeys()). That method causes contention on the > sequence generators which back identity columns. See > https://issues.apache.org/jira/browse/DERBY-6934. It is likely that you > have stumbled over this problem. You may be able to workaround this > problem by manually generating your object IDs yourself (e.g., by using > a sequence generator) and somehow forcing those object ids down through > the Hibernate api. I don't use Hibernate myself, so I don't know what > this entails. Maybe you will get better advice from someone who has > dealt with this Hibernate/Derby issue. ..so could this means that there is issue in hibernate? (meanwhile I will try to google it :)) Nevertheless, I am currious about this tooMuchContetionException. It is called in SequenceUpdater.getCurrentValueAndAdvance(..). However, this method is synchonized. So concurrent generation of Ids should not be problem (correct me if I am wrong). In method body there is comment > ...Lock contention is possible if someone has selected from SYSSEQUENCES > contrary to our advice. In that case, we raise a TOO MUCH CONTENTION > exception. I have one custom sequence in SYSSEQUENCES, and I am getting new value with query "VALUES (NEXT VALUE FOR my_seq)". Could this be the problem, or there could be some other? Besides this I am not using SYSSEQUENCES explicitly. -- Sent from: http://apache-database.10148.n7.nabble.com/Apache-Derby-Users-f95095.html
