I have a simple application that is running with no other access to the
database. A sequence is defined
CREATE SEQUENCE LOG_ENTRY_SEQUENCE AS BIGINT START WITH 1 MINVALUE 1 CYCLE
The application is retrieving the next sequence number with a "VALUES (NEXT
VALUE FOR LOG_ENTRY_SEQUENCE)" statement and then that sequence number is being
used as an ID for the rows to be inserted int another database table.
500,000 rows are going to be inserted. When this is run, periodically there
is an error being logged by derby.
Here is the derby.log
Tue Sep 19 15:55:06 EDT 2017:
Booting Derby version The Apache Software Foundation - Apache Derby - 10.13.1.1
- (1765088): instance a816c00e-015e-9bb4-c83b-ffffb4d52705
on database directory /opt/csemlogger/glassfish4/databases/csemloggerdb with
class loader sun.misc.Launcher$AppClassLoader@5c647e05
Loaded from file:/opt/csemlogger/glassfish4/javadb/lib/derby.jar
java.vendor=Oracle Corporation
java.runtime.version=1.8.0_40-b26
user.dir=/
os.name=SunOS
os.arch=amd64
os.version=5.10
derby.system.home=/opt/csemlogger/glassfish4/databases
Database Class Loader started - derby.database.classpath=''
Database Class Loader started - derby.database.classpath='CSEM.csemderby'
Derby could not obtain the locks needed to release the unused, preallocated
values for the sequence 'CSEM'.'LOG_ENTRY_SEQUENCE'. As
a result, unexpected gaps may appear in this sequence.
Derby could not obtain the locks needed to release the unused, preallocated
values for the sequence 'CSEM'.'LOG_ENTRY_SEQUENCE'. As
a result, unexpected gaps may appear in this sequence.
Derby could not obtain the locks needed to release the unused, preallocated
values for the sequence 'CSEM'.'LOG_ENTRY_SEQUENCE'. As
a result, unexpected gaps may appear in this sequence.
Derby could not obtain the locks needed to release the unused, preallocated
values for the sequence 'CSEM'.'LOG_ENTRY_SEQUENCE'. As
a result, unexpected gaps may appear in this sequence.
Here is the code used. Note that it is using JPA, however the LogEnty entity
being inserted is not using the sequence. All LogEntry ID assignment is done
manually using the result of the sequence number retrieved (the slot
assignment).
private static void initializeLoggerEntryTable(SetupContext ctx, long
entryCount) {
EntityManager em = ctx.getEntityManager();
Query nextSeqQuery = em.createNativeQuery("VALUES (NEXT VALUE FOR
LOG_ENTRY_SEQUENCE)");
int j = 0;
// Create a transaction
ctx.getEntityManager().getTransaction().begin();
for (int i = 0; i < entryCount; i++) {
long nextSeq = ((Long) nextSeqQuery.getSingleResult()).longValue();
long slot = nextSeq % entryCount;
// See if there is a LogEntry at this slot
LogEntry logEntry = em.find(LogEntry.class, slot);
if (null == logEntry) {
// There is not, so create one
logEntry = new LogEntry();
logEntry.setSlot(slot);
// Persist the chassis template
em.persist(logEntry);
}
// Commit the transaction
if (++j >= 10) {
em.getTransaction().commit();
em.clear();
em.getTransaction().begin();
j = 0;
}
}
ctx.getEntityManager().getTransaction().commit();
}
The sequence is not used outside of this code and there is no other access to
the database. I don't understand why some internal lock could not be obtained.
Any insight will be greatly appreciated.
________________________________
Canoga Perkins
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