Re: Clock sweep not caching enough B-Tree leaf pages?

On Wed, Apr 15, 2015 at 5:00 PM, Martijn van Oosterhout
<kleptog@svana.org> wrote:
> I've been following this thread from the side with interest and got
> twigged by the point about loss of information.  If you'd like better
> information about relative ages, you can acheive this by raising the
> cap on the usage count and dividing (or right-shifting) each sweep.

Yeah, I thought about that, too.  It might be worth experimenting with.

> This would allow you to remember much more about about the relative
> worth of often used pages.  With a cap of 32 you'd have the same effect
> as now where after 5 sweeps the buffer is evicted.  Mathematically the
> count would converge to the number of times the block is used per
> sweep.

Hmm, interesting point.  It's possible that we'd still have problems
with everything maxing out at 32 on some workloads, but at least it'd
be a little harder to max out at 32 than at 5.

-- 
Robert Haas
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