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Re: [HACKERS] Query cancel and OOB data (fwd)

From: Hal Snyder <hal(at)enteract(dot)com>
To: hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Query cancel and OOB data (fwd)
Date: 1998-06-01 05:33:35
Message-ID: 199806010533.BAA03855@hub.org (view raw or flat)
Thread:
Lists: pgsql-hackers
> From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
> Date: Mon, 1 Jun 1998 00:53:21 -0400 (EDT)
...
> > Just do time and pid. But get the time from gettimeofday so it will be
> > down to the millisecond or so. Anything more is overkill for this application.
> 
> You have given me exactly what I needed.  If I run gettimeofday() on
> postmaster startup, and run it when the first backend is started, I can
> use the microseconds from both calls to generate a truely random seed. 
> Even if the clock is only accurate to 10 ms, I still get a 10,000 random
> keyspace.  I can mix the values by taking/swapping the low and high
> 16-bit parts so even with poor resolution, both get used.
> 
> The micro-second times are not visible via ps, or probably even kept in
> the kernel, so these values will work fine.
> 
> Once random is seeded, for each backend we call random twice and return
> a merge of the two random values.  I wonder if we just call random once,
> and XOR it with our randeom seed, if that would be just as good or
> better?  Cryptologists?
> 
> Comments?  Sounds like a plan.  The thought of giving the users yet
> another option to disable cancel just made me squirm.

For FreeBSD and Linux, isn't /dev/urandom the method of choice for
getting random bits? [I've been away from this thread awhile - please
excuse if this option was already discussed].


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Next:From: Thomas G. LockhartDate: 1998-06-01 06:11:34
Subject: Re: [GENERAL] Re: [HACKERS] custom types and optimization
Previous:From: Bruce MomjianDate: 1998-06-01 04:53:21
Subject: Re: [HACKERS] Query cancel and OOB data (fwd)

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