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From Matt Pouttu-Clarke <Matt.Pouttu-Cla...@icrossing.com>
Subject Multi-thread access to read-only DB in embedded mode?
Date Thu, 06 Jan 2011 15:53:42 GMT
Hi All,

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).

I have already tried embedding the network server and client with a
localhost loopback and it made the code 10 times slower.  So if anyone has
been able to overcome this limitation without using the network server and
client I would be very interested.


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