Re: Cost Based Optimizier
Date: 1996/08/01
Message-ID: <4tp3r0$jpr_at_mtinsc01-mgt.ops.worldnet.att.net>#1/1
djetz_at_spots.ab.ca (Doris Jetz) wrote:
>I mentioned somewhere else in this newsgroup a while ago and I think
>it might be useful here.
>
>When analyzing tables, don't use estimate, use compute on all tables
>any time you analyze for statistics. This is coming from a local
>(here in Calgary) oracle technical expert. He said that the estimates
>aren't accurate enough at this point and may result in really crappy
>execution paths.
>
>Hope this helps.
>
>
>Doris Jetz
>
>
>richu_at_msn.com (Richard Hu) wrote:
>
>> We have a 7.1.3.2.1 production system and have just ANALYZED all the
>> tables and indexes.
>> Since we have done this we are suffering with response times from queries
>> that join two and more tables.
>> When EXPAINed/TKPROFed we have discovered that some selects are
>> performing full tables scans.
>> It appears that the execution plans worked out by the optimizer are not
>> the best.
>> (I have checked that all the tables and indexes are analyzed -
>> the statistics were ESTIMATEd on all but one table which was be
>> COMPUTEd.)
>>
>Oracle DBA/Developer
>NGX Canada Inc.
>Calgary, AB
>
Wow! We always use ESTIMATE in our shop because COMPUTE takes so darn long. I will run some experiments on some of our smaller tables and see what the difference is.
Carolyn Stephenson, Dept. of Veterans Affairs
cs1_at_mail.va.gov or stephenson.carolyn_at_forum.va.gov Received on Thu Aug 01 1996 - 00:00:00 CEST