Re: Different Plans for Literal Vs Bind Variables
- From: Ian MacGregor <ian@xxxxxxxxxxxxxxxxx>
- To: Oracle-L Freelists <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 09 Jan 2009 16:15:05 -0800
It was more than an assumption. The database had just been rebooted and no
one was working at that time, and the statement was not run that would have
been generated by someone else. However, just in case I got the SQL_id and
then flush the shared pool and checked to see if the statement was in the
library cache via v$sql. It was not so I tried the experiment again
Again the query plans differ. I know they should not but they do.
Ian
On 1/9/09 3:14 PM, "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx> wrote:
> The phrase "would not have been" indicates an assumption to me and you know
> what happens when we assume :-) I would leave nothing to chance and chec
> v$sql for the specific hash_value that appears in your raw 10046 trace file to
> be 100% positive that the query is not loaded in your library cache before you
> run it with the desired bind variable value. Then, if you verify that it gets
> hard parsed with the desired bind value and still doesn't get the same plan as
> the literal, I think your next step is to run two 10053 traces and diff them.
> In case you're not familiar with the 10053 trace, here's a good place to
> start:
>
> http://www.centrexcc.com/A%20Look%20under%20the%20Hood%20of%20CBO%20-%20the%20
> 10053%20Event.pdf
>
> Regards,
> Brandon
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
> Behalf Of Ian MacGregor
>
> The statements were new so they
> would not have been in the library cache, and the values reported for the
> 10046 level 12 trace matched those in the query with literals
>
>
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