Ed,
Thanks for that...I wasn't even aware of the 'exceptions into
exceptions_table' clause. Unfortunately for me it's not duplicated I'm
deleting, it's just a shed load of data :(
regards,
K.
"hit any user to continue"
__________________
Kevin Thomas
Technical Analyst
Deregulation Services
Calanais Ltd.
(2nd Floor East - Weirs Building)
Tel: 0141 568 2377
Fax: 0141 568 2366
http://www.calanais.com
-----Original Message-----
Sent: 12 September 2001 10:55
To: Multiple recipients of list ORACLE-L
Hi Kevin and Suhen,
I believe that there are only two variants that
appropriate for such huge tables.
1. I remember a good tip from Steve Adams. He recommended
to use CTAS or INSERT AS SELECT for a similar case.
Of course, this method requires a lot of free space.
2. You may think about enabling PK or UNIQUE constraint on
the column with 'exceptions into exception_table' clause.
You'll find rowids of duplicates in the 'exception table'
I have no expierence with such huge tables. I only can guess that
the first method win.
Don't use correlate subqueries to find duplicates, they will run
forever
Regards,
Ed
>
>
> Suhen,
>
> I have a similar problem at the moment although its 900
> million rows of
> which we want to delete approx. 200 million (they obviously
> never asked you
> guys for help with their design!). Unfortunately we have
> just decided to
> take the hit with downtime to correct the problem. We have
> scheduled 3 days
> for downtime including taking a backup before doing
> anything. I would just
> let it run, but notify the users that either they can expect
> performance
> degredation if they continue to work while you delete, or
> lock them out from
> the database for a while until it's finished running.
>
> I don't think indexes will help you in this situation
> (although correct me
> if I'm wrong anyone).
>
> K.
>
> -----Original Message-----
> Sent: 12 September 2001 05:50
> To: Multiple recipients of list ORACLE-L
>
>
>
> List,
>
>
>
> I need to delete duplicate records from a very large table
> (60 millions
> records +).
>
> There would be about 3 million duplicate entries.
>
>
>
> What is the quickest way to do this?
>
>
>
> The syntax that I am using is
>
> delete from invaudee
>
> where rowid not in (select min(rowid) from invaudee
>
> group by audit_number);
>
>
>
> This is taking a long time to run. I cannot see any entries
> in v$transaction
>
> for the delete.
>
>
>
> There is no indexes on the INVAUDEE table.
>
> I created an index on the primary key column but it still
> takes forever to
> run.
>
>
>
> I do not have the space to CTAS.
>
>
>
> Or should I write the duplicates to an EXCEPTIONS table and
> perform the
> delete based on the entries
>
> in the EXCEPTIONS table.
>
>
>
> Any help would be greatly appreciated.
>
>
>
> Suhen
>
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Thomas, Kevin
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