Re: CBO bug with global index ?

Hi David,

 > CBO bug with global index ?

to combine two indices with OR condition they must by converted to bitmaps 
first.

Global bitmap index are not supported. I'm not really sure if the conversion 
of a global index to bitmap index is impossible, but I never observed it. 
I'd speculate that this is not possible and it is the reason of the full 
scan with global indexes.

Any on list can confirm or disprove this?



IMHO two global indexes can only be combined on AND condition (see hint 
AND_EQUAL)



Anyway in your example I'd recommend to *use* local index (especially if you 
deploy exchange partition). Based on the way how the table is populated you 
may consider to use local bitmap index.



HTH



Jaromir D.B. Nemec

http://www.db-nemec.com

----- Original Message ----- 
From: "David Feng" <dbanotes@xxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Friday, May 27, 2005 11:41 AM
Subject: CBO bug with global index ?


| 6 | BITMAP OR | | | | | | |
| 7 | BITMAP CONVERSION FROM ROWIDS | | | | | | |
|* 8 | INDEX RANGE SCAN | IND_TRADE_BASE_BACCOUNT | | | 43 | 1 | 21 |
| 9 | BITMAP CONVERSION FROM ROWIDS | | | | | | |
|* 10 | INDEX RANGE SCAN | IND_TRADE_BASE_SACCOUNT | | | 44 | 1 | 21 |
| 11 | VIEW | VW_NSO_1 | 8168 | 7992K| 11 | | |
| 12 | COLLECTION ITERATOR PICKLER FETCH| STR2VARLIST | | | | | |
| 13 | TABLE ACCESS FULL | DUAL | 8168 | | 11 | | |
------------------------------------------------------------------------------------------------------------------------



SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
PL/SQL Release 9.2.0.4.0 - Production
CORE 9.2.0.3.0 Production
TNS for Linux: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production

 Thanks for any help!
!

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