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Re: de-dup process

From: Tony van Lingen <>
Date: Thu, 14 Dec 2006 12:02:16 +1000
Message-ID: <>

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
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Information Management
Corporate Development Division
Environmental Protection Agency

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Received on Wed Dec 13 2006 - 20:02:16 CST

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