From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Neil Conway <nconway(at)klamath(dot)dyndns(dot)org> |
Cc: | PostgreSQL Patches <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: new hash function |
Date: | 2002-03-05 06:35:50 |
Message-ID: | 200203050635.g256ZoJ25093@candle.pha.pa.us |
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Thread: | |
Lists: | pgsql-hackers pgsql-patches |
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.
---------------------------------------------------------------------------
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(at)rogers(dot)com>
> PGP Key ID: DB3C29FC
[ Attachment, skipping... ]
>
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--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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