Re: Object Ownership v/s Parsed Query

Hi.

Thanks for your expalanation. Could you please guide me to the paper by Steve Adams you have talked about in the answer - URL or web-site, wherever the paper appears!!!

Thanks.
S

yong321_at_yahoo.com (Yong Huang) wrote in message news:<b3cb12d6.0108012029.3ea3fbaa_at_posting.google.com>...
> It would help if you could read the Concept manual. There's no
> ambiguity when parsing the first two SQLs. For the 3rd one, Oracle
> tries to find table MyTab in C's schema (suppose ALTER SESSION SET
> CURRENT_SCHEMA is not done). It's there! So a full table scan is
> performed on it. If it's not found, it may be a view; failing that, it
> may be a private synonym; failing that, public synonym; failing that,
> you get ORA-942.
>
> When another session executes "Select * from MyTab" for the 1st time,
> it finds this SQL in library cache. It performs authentication (it
> always has to do this) and sees if it's his own table, view, private
> synonym...
>
> It's always a good idea to specify owner's name if the table is not
> your own than using a synonym. Steve Adams has done some benchmark in
> his recent newsletter.
>
> Yong Huang
> yong321_at_yahoo.com
>
> learning_still_at_hotmail.com (Newbie) wrote in message news:<6093c29e.0108010924.2db6103d_at_posting.google.com>...
> > If a table, say MyTab is created by users A, B and C within their
> > respective default tablespaces, A.MyTab and C.MyTab having same
> > structures but b.MyTab have different structure. Now if user C issues
> > following statements -
> >
> > Select * from A.MyTab
> > Select * from B.MyTab
> > Select * from MyTab
> >
> > - How are the queries parsed?
> > - How is their execution plan identified?
> > - Will exec plan be different for all?
> > - If it is different for all, isn't it always a better practice to
> > qualify the table name with owner name within front-end code?
> > - What about cost of query and reusability of the query once it is
> > parsed? In what cases same parsed one could be used?
Received on Thu Aug 02 2001 - 15:14:27 CDT