Re: "Hash index" vs. "b-tree index" (PostgreSQL 8.0)

From: Neil Conway <neilc(at)samurai(dot)com>
To: Ying Lu <ying_lu(at)cs(dot)concordia(dot)ca>
Cc: pgsql-general(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org
Subject: Re: "Hash index" vs. "b-tree index" (PostgreSQL 8.0)
Date: 2005-05-09 14:36:42
Message-ID: 427F757A.8000407@samurai.com
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Ying Lu wrote:
> May I know for simple "=" operation query, for "Hash index" vs. "B-tree"
> index, which can provide better performance please?

I don't think we've found a case in which the hash index code
outperforms B+-tree indexes, even for "=". The hash index code also has
a number of additional issues: for example, it isn't WAL safe, it has
relatively poor concurrency, and creating a hash index is significantly
slower than creating a b+-tree index.

-Neil

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