Re: What is wrong with hashed index usage?

From: Neil Conway <nconway(at)klamath(dot)dyndns(dot)org>
To: "Dann Corbit" <DCorbit(at)connx(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: What is wrong with hashed index usage?
Date: 2002-04-22 22:13:48
Message-ID: 20020422181348.3296b6f6.nconway@klamath.dyndns.org
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On Mon, 22 Apr 2002 15:04:22 -0700
"Dann Corbit" <DCorbit(at)connx(dot)com> wrote:
> Here is where a hashed index shines:
> To find a single item using a key, hashed indexes are enormously faster
> than a btree.
>
> That is typically speaking. I have not done performance benchmarks with
> PostgreSQL.

Yes -- but in the benchmarks I've done, the performance different
is not more than 5% (for tables with ~ 600,000 rows, doing lookups
based on a PK with "="). That said, my benchmarks could very well
be flawed, I didn't spend a lot of time on it. If you'd like to
generate some interest in improving hash indexes, I'd like to see
some empirical data supporting your performance claims.

Cheers,

Neil

--
Neil Conway <neilconway(at)rogers(dot)com>
PGP Key ID: DB3C29FC

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