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From Kathey Marsden <kmarsdende...@sbcglobal.net>
Subject Re: Multi-thread access to read-only DB in embedded mode?
Date Thu, 06 Jan 2011 16:29:31 GMT
On 1/6/2011 7:53 AM, Matt Pouttu-Clarke wrote:
> Hi All,
>
> I am using Derby as an embedded database within a Hadoop job to lookup 
> IP geographic info.
> http://mpouttuclarke.wordpress.com/2010/12/10/java-embedded-db-for-ip2location-in-hadoop/
>
> 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).
>
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.


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