Re: new hash function

Your patch has been added to the PostgreSQL unapplied patches list at:

    http://candle.pha.pa.us/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

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Neil Conway wrote:
> I've attached a patch which implements Bob Jenkin's hash function for
> PostgreSQL. This hash function replaces the one used by hash indexes and
> the catalog cache. Hash joins use a different, relatively poor-quality
> hash function, but I'll fix that later.
>
> As suggested by Tom Lane, this patch also changes the size of the fixed
> hash table used by the catalog cache to be a power-of-2 (instead of a
> prime: I chose 256 instead of 257). This allows the catcache to lookup
> hash buckets using a simple bitmask. This should improve the performance
> of the catalog cache slightly, since the previous method (modulo a
> prime) was slow.
>
> In my tests, this improves the performance of hash indexes by between 4%
> and 8%; the performance when using btree indexes or seqscans is
> basically unchanged.
>
> Unless anyone seems a problem, please apply.
>
> Cheers,
>
> Neil
>
> --
> Neil Conway <neilconway@rogers.com>
> PGP Key ID: DB3C29FC

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