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Re: [PERFORM] "Hash index" vs. "b-tree index" (PostgreSQL

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Jim C(dot) Nasby" <decibel(at)decibel(dot)org>
Cc: Neil Conway <neilc(at)samurai(dot)com>,Christopher Petrilli <petrilli(at)gmail(dot)com>,Ying Lu <ying_lu(at)cs(dot)concordia(dot)ca>, pgsql-general(at)postgresql(dot)org,pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] "Hash index" vs. "b-tree index" (PostgreSQL
Date: 2005-05-10 18:07:00
Message-ID: 20884.1115748420@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-performance
"Jim C. Nasby" <decibel(at)decibel(dot)org> writes:
> Well, in a hash-join right now you normally end up feeding at least one
> side of the join with a seqscan. Wouldn't it speed things up
> considerably if you could look up hashes in the hash index instead?

That's called a "nestloop with inner index scan", not a hash join.

			regards, tom lane

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