Re: Is it safe to switch off cost based optimizing?

In article <dischner-3001951403160001_at_gkc12a.klch.med.uni-muenchen.de> dischner_at_med.uni-muenchen.de (Anton Dischner) writes:
>Hi Marty,
>
>you may want to set rule based optimization for your current session only.
>You can use: alter session set optimizer_goal = rule;

ok. I'll try that to look _at_ explain plan differences for all of our apps.

>> We are currently using the cost based optimizer, but would like to switch
>> to rule based. Will switching strategies alter the execution plan for
>> extraction (and screw up the extraction order)?
>
>Yes! (Did so in many cases for me), don't know anything about order, for
>my understanding only an 'order by' guarantees correct sorting.

You are correct. I can run an extraction in 20 minutes using my unclean technique that takes several days and several GB of temp space using a clean "order by".

>> We have NEVER run an analyze against any table.
>>
>The you are using the rule based anyway!?

I understand that's the default w/o any analyze runs, thought I'd check this group to be sure, tho.

>Best regards,
>
>Toni

Thanx for the input,
Marty Received on Tue Jan 31 1995 - 17:58:59 CET