Re: Explain Plan Gives 0 Cost.

Hi Cherles,
Not true. You would get position equal to a number ( for plan_table.id = 0 ) only when the optimizer_mode is COST. It will be null when using RULE-based optimization.

-- 
Cheers

Sridhar Subramaniam
Avion Consulting Services
Sydney - Australia
email : avion_at_ozemail.com.au / ssubrama_at_nibucorp.ccdn.otc.com.au

Disclaimer : All opinions are truly and just mine.


Charles_Dye_at_corp.dialog.com (Charles Dye (PC)) wrote:


>All, 


>

>Why is this happening?  V7.0.16 and V7.1.3

>

>SQL> delete from plan_table

>  2  /

>

>6 rows deleted.

>

>SQL> explain plan 

>  2  for

>  3  select a.username, a.user_id, b.profile

>  4  from a, b

>  5  where a.user_id = b.user_id

>  6  and b.created < sysdate

>  7  and  b.profile != 'DEFAULT'

>  8  /

>

>Explained.

>

>SQL> select id, parent_id, position

>  2  from plan_table;

>

>	ID  PARENT_ID	POSITION

>---------- ---------- ----------

>	 0                              <<<<< Null here corresponds to Cost = 0

>	 1	    0	       0

>	 2	    1	       1

>	 3	    2	       1

>	 4	    1	       2

>	 5	    4	       1

>

>6 rows selected.

>