Re: bitmap index not used
Which version of the database? Do you have any special setup? Any optimizer parameters on either session or system level? On 10/29/2003 03:09:39 PM, Josh Collier wrote: Hi, I have a puzzle. A bitmap index on a varchar2(25) column. table has 7131413 rows, of which 7125290 are null for the column in question, the rest of the rows are unique values. There is a histogram on this column, it has 2 buckets. A select statement using this column in the where clause generates two plans, one which uses the index and one which doesn't. The deciding factor is the length of the string in the filter. select * from table where microchip_number = 'avid1' this produces a plan which uses the bitmap select * from table where microchip_number = 'avid12' (and any additional characters in the string ) this produces a plan which uses a full table scan. I am stumped about how to figure out why the optimizer makes a choice based upon the length of the string in the predicate. Much obliged, Josh -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Josh Collier INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Mladen Gogala Oracle DBA Note: This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. Wang Trading LLC and any of its subsidiaries each reserve the right to monitor all e-mail communications through its networks. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of any such entity. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mladen Gogala INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
RE: bitmap index not used
version 8.1.7.4 optimizer parameters are default. -Original Message- Sent: Wednesday, October 29, 2003 12:34 PM To: Multiple recipients of list ORACLE-L Which version of the database? Do you have any special setup? Any optimizer parameters on either session or system level? On 10/29/2003 03:09:39 PM, Josh Collier wrote: Hi, I have a puzzle. A bitmap index on a varchar2(25) column. table has 7131413 rows, of which 7125290 are null for the column in question, the rest of the rows are unique values. There is a histogram on this column, it has 2 buckets. A select statement using this column in the where clause generates two plans, one which uses the index and one which doesn't. The deciding factor is the length of the string in the filter. select * from table where microchip_number = 'avid1' this produces a plan which uses the bitmap select * from table where microchip_number = 'avid12' (and any additional characters in the string ) this produces a plan which uses a full table scan. I am stumped about how to figure out why the optimizer makes a choice based upon the length of the string in the predicate. Much obliged, Josh -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Josh Collier INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Mladen Gogala Oracle DBA Note: This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. Wang Trading LLC and any of its subsidiaries each reserve the right to monitor all e-mail communications through its networks. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of any such entity. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mladen Gogala INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Josh Collier INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
Re: bitmap index not used
I'd recommend you to take a dump. A 10053 dump. And see from there. :) Tanel. - Original Message - To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED] Sent: Wednesday, October 29, 2003 10:09 PM Hi, I have a puzzle. A bitmap index on a varchar2(25) column. table has 7131413 rows, of which 7125290 are null for the column in question, the rest of the rows are unique values. There is a histogram on this column, it has 2 buckets. A select statement using this column in the where clause generates two plans, one which uses the index and one which doesn't. The deciding factor is the length of the string in the filter. select * from table where microchip_number = 'avid1' this produces a plan which uses the bitmap select * from table where microchip_number = 'avid12' (and any additional characters in the string ) this produces a plan which uses a full table scan. I am stumped about how to figure out why the optimizer makes a choice based upon the length of the string in the predicate. Much obliged, Josh -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Josh Collier INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Tanel Poder INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
RE: bitmap index not used
Probably the histogram is deciding that. Remove the histogram and see if there is any changes. Waleed -Original Message- Sent: Wednesday, October 29, 2003 3:10 PM To: Multiple recipients of list ORACLE-L Hi, I have a puzzle. A bitmap index on a varchar2(25) column. table has 7131413 rows, of which 7125290 are null for the column in question, the rest of the rows are unique values. There is a histogram on this column, it has 2 buckets. A select statement using this column in the where clause generates two plans, one which uses the index and one which doesn't. The deciding factor is the length of the string in the filter. select * from table where microchip_number = 'avid1' this produces a plan which uses the bitmap select * from table where microchip_number = 'avid12' (and any additional characters in the string ) this produces a plan which uses a full table scan. I am stumped about how to figure out why the optimizer makes a choice based upon the length of the string in the predicate. Much obliged, Josh -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Josh Collier INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Khedr, Waleed INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
