Received: from localhost.localdomain (postgresql.org [64.49.215.8]) by localhost (Postfix) with ESMTP id 8CC9D4775FB for ; Wed, 19 Jun 2002 13:26:58 -0400 (EDT) Received: from candle.pha.pa.us (216-55-132-35.dsl.san-diego.abac.net [216.55.132.35]) by postgresql.org (Postfix) with ESMTP id A8EF2476F71 for ; Wed, 19 Jun 2002 12:43:05 -0400 (EDT) Received: (from pgman@localhost) by candle.pha.pa.us (8.11.6/8.10.1) id g5JGh4D10793; Wed, 19 Jun 2002 12:43:04 -0400 (EDT) From: Bruce Momjian Message-Id: <200206191643.g5JGh4D10793@candle.pha.pa.us> Subject: Re: SQL performance issue with PostgreSQL compared to MySQL In-Reply-To: <4193.1024496331@sss.pgh.pa.us> To: Tom Lane Date: Wed, 19 Jun 2002 12:43:04 -0400 (EDT) Cc: Jeff Self , pgsql-sql@postgresql.org X-Mailer: ELM [version 2.4ME+ PL97 (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-Archive-Number: 200206/252 X-Sequence-Number: 8217 Tom Lane wrote: > Jeff Self writes: > > if it's too OT, let me know, and I'll stop. The query "SELECT authuser, > > SUM(bytes) AS traffic FROM logfile GROUP BY authuser ORDER BY traffic" > > [is slow] > > What datatype are the columns used in the query? And what PG version > are we talking about? My guess is that is the lack of hashing for GROUP BY aggregating that is killing us. TODO has: * Add hash for evaluating GROUP BY aggregates and I specifically remember MySQL has such a hash. The big question is how many unique values are there in the group. If it is large, the missing hashing could be the problem. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026