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Re: 5.8.2 and 5.8.n binary compatibility

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Nicholas Clark
November 3, 2003 13:07
Re: 5.8.2 and 5.8.n binary compatibility
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On Mon, Nov 03, 2003 at 10:16:06AM +0000, Alan Burlison wrote:

> What is your intention for how 5.8.n where 'n' is >= 3 will handle the hash 
> key binary compatibility issue?  At what point will we break backwards 
> binary compatibility and just have *all* hashing use the seed with no 'Oh 
> dear I'm under attack, switch behaviour' logic?  Obviously there is a 
> performance hit for this 5.8.0/5.8.1 binary compatibility stuff, and I did 
> get the impression that at some point we would switch over entirely to the 
> new mechanism.
> I think it needs to be clearly documented in 5.8.2 somewhere that we will 
> at some point break binary compatibility, so people can prepare for it.



[I think that answers the 5.8.n question - 5.8.n for all n > 1]

> Also, I don't actually care about 5.8.0/5.8.1 binary compatibility, as we 
> didn't ship either version.  I'd therefore like to permenantly enable the 
> new behaviour so that I don't have to take a potential prrformance hit, and 
> so I don't have to break binary compatibility in the future.  Is there 
> going to be a Configure flag to allow me to do this?

There isn't one currently, and I can't see one going in before release.
Given that the cut in threshold is a linked list of 14 elements, it
shouldn't happen with regular data, and even with the rehashing may well
be faster than 5.8.1

I'd suggest benchmarking.

Nicholas Clark

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