On Sat, Sep 24, 2005 at 10:34:42AM +0200, Thomas Hallgren wrote: > Oliver Jowett wrote: > >I assume this means you have a single lock serializing requests to the > >backend? > > > Yes, of course. I also make sure that the main thread cannot return > until another thread that is servicing a backend request has completed. > There's absolutely no way two threads can execute backend code > simultaniously.
Ok, I have a question. PostgreSQL uses sigsetjmp/siglongjmp to handle errors in the backend. If you're changing the stack, how do you avoid the siglongjmp jumping back to a different stack? Or do you somehow avoid this problem altogether? > I though about that. The drawback is that each and every call must spawn > a new thread, no matter how trivial that call might be. If you do a > select from a table with 10,000 records and execute a function for each > record, you get 20,000 context switches. Avoiding that kind of overhead > is one of the motivating factors for keeping the VM in-process. Well, on linux at least context switches are quite cheap. However, how does Java handle the possibility that functions never return. Do you wrap each call in a PG_TRY/PG_CATCH to propegate errors? Tricky issues... -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
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