Re: Improving Performance of Hash Joins

From: Mladen Gogala <>
Date: Tue, 30 Dec 2008 13:35:27 +0000 (UTC)
Message-ID: <gjd82v$ivs$>

On Thu, 25 Dec 2008 21:04:03 -0800, DA Morgan wrote:

> Your assumption that you can not modify the queries is incorrect. You
> can easily do so with the DBMS_ADVANCED_REWRITE built-in package.

Quite unrelated to this debate, this is one of the dirtiest tricks introduced by the Oracle10g. Using DBMS_ADVANCED_REWRITE on the SQL written by the 3rd party without actually modifying the source code and losing support was something that really thrilled my management. The vendor in question later compared plans and SQL statements, blushed and made it a part of the official release. It's very underused and not very popular, just like V$%_METRIC and V$%_METRIC_HISTORY tables or expression filtering. Expression filtering is also an excellent thing that I've seen used only once.

Mladen Gogala
Received on Tue Dec 30 2008 - 07:35:27 CST

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