Re: de-dup process

  • From: Tony van Lingen <tony.vanlingen@xxxxxxxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Thu, 14 Dec 2006 12:02:16 +1000

A Ebadi wrote:

> Biggest problem we've faced in coming up with a solution is none of 
> the solutions so far scale.  In other words, things are fine if we 
> have a 20 million row table with 2-3 million duplicates - runs in 
> 10-15 minutes.  However, trying it for 100+ million row table - it 
> runs for hrs!

You do of course delete non-redoable? When deleting a row, Oracle will 
create redo info which you, having done a direct load, will not be 
needed. This'll take time.

> We've even had another tool (Informatica) select out the ROWIDs of the 
> duplicates into a separate table then we are using PL/SQL cursor to 
> delete those rows from the large table, but this doesn't scale either!

if you mean that deleting 20million rows from a huge tabel is not as 
fast as deleting 2, then no. Nothing will scale. Try buying more iron 
and use parallel query.

Why don't you look at cleansing the dataset before loading it? e.g. use 
'sort -u' on the file to get rid of duplicate lines. Might be quicker 
than loading everything and deleting later on...


Tony van Lingen
Tech One Contractor
Information Management
Corporate Development Division
Environmental Protection Agency

Ph:     (07) 3234 1972
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E-mail: tony.vanlingen@xxxxxxxxxxxxxx

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