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Subject: [Pljava-dev] [HACKERS] Shared memory
Date: Mon, 27 Mar 2006 16:15:38 +0200
Message-ID: <4427F38A.6090408@tada.se> (raw)
In-Reply-To: <A760BE24-97E1-4B3D-9F5F-7D5F4D2D1E62@sptci.com>
References: <4423CF32.3060406@tada.se>
	<20060324125851.GC8718@svana.org>
	<4427A8F1.3020009@tada.se>
	<20060327104506.GB30791@svana.org>
	<4427DF17.7040700@tada.se>
	<A760BE24-97E1-4B3D-9F5F-7D5F4D2D1E62@sptci.com>

Rakesh Vidyadharan wrote:
> I agree with your view of connection pools.  The only time I wished 
> that PL/Java did not have such a "heavy" initialisation requirement 
> was when I needed to use a Java stored procedure from C (it was too 
> trivial to explore using a connection pool).  I ended up writing an 
> equivalent stored procedure in pgsql.  This may be a major issue for 
> some people, since one of the main benefits of using stored procedures 
> is that your database logic becomes available to multiple technologies.
Good point.


>
> In my view the main benefit that may be derived form using a shared 
> JVM is that you may be able to support more connections.  Maybe you 
> can just wait for the multi-tasking JVM to arrive on the scene.  I am 
> not sure how far the Java committee is on that, but there has been 
> talk of developing one for quite a while now.
>

I think you mean the JSR121, where many JVM's can share resources by 
running as "Java Isolates" in a MVM?. Unfortunately that will not help 
much. A PostgreSQL backend process will still need to use ipc in order 
to talk to the MVM process. What would help is if multiple JVM's, each 
running as a separate process, could share a lot of resources but I 
haven't seen any viable effort in that direction. I doubt it's doable 
without major parts of the JVM being built into the kernel.

Regards,
Thomas Hallgren

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