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From: Vivek Khera <vivek@khera.org>
Date: Mon, 3 Apr 2006 14:22:23 -0400
To: freebsd-stable <freebsd-stable@freebsd.org>
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Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] semaphore usage "port based"? 
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On Apr 3, 2006, at 12:37 PM, Tom Lane wrote:

> semaphore keys on each cycle of life, so you'd have to get fooled by
> chance coincidence of existing PIDs every time over many cycles to
> have a severe resource-leakage problem.  (BTW, Marc, that's the reason
> for *not* randomizing the key selection as you suggested.)

Seems to me the way around this with minimal fuss is to add a flag to  
postgres to have it  start at different points in the ID sequence.   
So pg#1 would start at first position, pg#2 second ID position, etc.   
then just hard-code an "instance ID" into the startup script for each  
pg.  No randomization make it easier to debug, and unique IDs make it  
avoid clashes under normal cases.