Oracle-L: Re: stats and query plans

From: Mark Richard <mrichard_at_transurban.com.au>
Date: Sun, 10 Aug 2003 15:59:28 -0800
Message-ID: <F001.005C9F26.20030810155928@fatcity.com>

Perhaps using an index isn't the best approach? When you say the queries run remarkably well how do you define this? If you are running the query in TOAD, for example, you might be returning just the first page of results where CBO has chosen an all rows approach - slower to start but quicker overall.

I'm not saying this is your problem but it's something to be careful of - I've been bitten several times in the past when trying to tune something quickly... As recently as last week. It looked great until I realised it was only the beginning of the result.

Regards,

Mark.

                                                                                                                                      
                      Sai Selvaganesan                                                                                                
                      <ssaisundar_at_sbcgl        To:       Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>                  
                      obal.net>                cc:                                                                                    
                      Sent by:                 Subject:  stats and query plans                                                        
                      ml-errors_at_fatcity                                                                                               
                      .com                                                                                                            
                                                                                                                                      
                                                                                                                                      
                      11/08/2003 05:54                                                                                                
                      Please respond to                                                                                               
                      ORACLE-L

a very basic question

i have faced this issue a few times in the last couple of weeks. we have a few queries that seem to run remarkable well in rule based optimisation than in choose based optimisation. the queries, with all the object stats collected upto date, never returns a result while when i deleted all stats it returns a result in no time.The plans are diffrent and w/o stats indexes are being used.

when this happens in the same system what are the things i should check. is it not recommended that oracle CBO is the best way to go in performance tuning and query optimisations.then how come rule based turns out to be efficient.surely i havent generated 10053 trace and gone through it but it doesnt make sense why CBO falters. Logically speaking when rule based path gives a result,CBO should choose that explain plan.

can someone throw some light on this

thanks
sai

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
   Privileged/Confidential information may be contained in this message.
          If you are not the addressee indicated in this message
       (or responsible for delivery of the message to such person),
            you may not copy or deliver this message to anyone.
In such case, you should destroy this message and kindly notify the sender
           by reply e-mail or by telephone on (61 3) 9612-6999.
   Please advise immediately if you or your employer does not consent to
                Internet e-mail for messages of this kind.
        Opinions, conclusions and other information in this message
              that do not relate to the official business of
                         Transurban City Link Ltd
         shall be understood as neither given nor endorsed by it.
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>






<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Privileged/Confidential information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such a case, you should destroy this message and kindly notify the sender by reply e-mail or by telephone on (03) 9612-6999 or (61) 3 9612-6999. Please advise immediately if you or your employer does not consent to Internet e-mail for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of Transurban Infrastructure Developments Limited and CityLink Melbourne Limited shall be understood as neither given nor endorsed by them.
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Mark Richard
  INET: mrichard_at_transurban.com.au

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: ListGuru_at_fatcity.com (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).

Received on Sun Aug 10 2003 - 18:59:28 CDT