On 1/6/2011 7:53 AM, Matt Pouttu-Clarke wrote:
Multi-thread access to read-only DB in embedded mode?
Embedded definitely supports more than one thread at a time as long
as all of those threads are in the same JVM. Each thread should
just have it's own separate Connection.
I am using Derby as an embedded database within a Hadoop job
to lookup IP geographic info.
The problem is that Hadoop has an option called JVM sharing
where more than one thread may be active in the JVM instance.
Since the embedded option only supports one thread at a time,
I have had to turn off JVM sharing for my IP lookup job (by
setting mapred.job.reuse.jvm.num.tasks to 1).