Re: bitmap conversion to rowids operation with btree indexes?
- From: "Mark J. Bobak" <mark@xxxxxxxxx>
- To: Jonathan Lewis <jonathan@xxxxxxxxxxxxxxxxxx>
- Date: Tue, 11 Jan 2005 19:57:47 -0500
On Tue, 2005-01-11 at 11:12, Jonathan Lewis wrote:
Jonathan,
Any thoughts on how to temper the CBO's desire to use this access path,
short of cutting it off alltogether, via _btree_bitmap_plans=FALSE?
-Mark
<much good info about btree bitmap plans deleted to avoid overquoting>
> The default value is FALSE in 8i, and true in 9i,
> and some people have reported performance
> problems because there setup started doing this
> conversion too frequently in inappropriate cases.
>
>
> Regards
>
> Jonathan Lewis
>
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
> The Co-operative Oracle Users' FAQ
>
> http://www.jlcomp.demon.co.uk/seminar.html
> Public Appearances - schedule updated Dec 23rd 2004
>
>
>
>
>
>
> ----- Original Message -----
> From: <ryan_gaffuri@xxxxxxxxxxx>
> To: <oracle-l@xxxxxxxxxxxxx>
> Sent: Tuesday, January 11, 2005 3:54 PM
> Subject: bitmap conversion to rowids operation with btree indexes?
>
>
> I see this operation in plans occasionally when I'm using btree indexes and
> there are not any bitmaps. I also see:
> BITMAP OR
>
> when using 2 btree indexes in the plan.
>
> does oracle do some conversion to bits to optimize certain plans even
> without bitmap indexes?
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
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--
Mark J. Bobak
mark@xxxxxxxxx
"Science is the belief in the ignorance of experts." --Richard P.
Feynman
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