Re: need to understand merge join cartesian plan

From: Greg Rahn <>
Date: Sun, 17 Jan 2010 10:02:31 -0800
Message-ID: <>

I know of a bug (8292914) which fits a similar description (not sure if it is publicly viewable). I filed it against where the MJC cardinality is calculated wrong - its only the cardinality of one side of the join, not the left * right. I'm not sure it if is present in previous releases.

The workaround is to set _optimizer_mjc_enabled=false to disable the MJC.

On Sun, Jan 17, 2010 at 7:14 AM, joshuasingham <> wrote:
> I have a excerpt for a execution plan that look like below  which i
> got from dbms.xplan display cursor and would like to know why when the
> merge join cartesian happens Oracle estimate that the will be only 1
> row return should it not be 36080 * 1 = 36080 as this is a Cartesian
> join the Db version is

Greg Rahn
Received on Sun Jan 17 2010 - 12:02:31 CST

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