RE: Delete + Insert versus Update

From: Ric Van Dyke <ric.van.dyke_at_hotsos.com>
Date: Thu, 16 Feb 2006 09:53:51 -0600
Message-ID: <C970F08BBE1E164AA8063E01502A71CF453C31@WIN02.hotsos.com>

Also don't forget all the redo generated.

A delete and reinsert could easily be 4+ times more expensive then an update.

Ric Van Dyke
Hotsos Enterprises
Cell 248-705-0624

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-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Norman Dunbar Sent: Thursday, February 16, 2006 10:34 AM To: oracle-l_at_freelists.org; peters_at_mitre.org Subject: Re: Delete + Insert versus Update

Peter,

My initial, off the top of my head, thought is simple :

in an UPDATE, the undo holds the before 'image' of the changed columns.
In a DELETE, the whole row is in the undo. An INSERT, as far as I remember, holds the rowid as all it has to do is delete the row.

So straight away there's a difference.

As for indexes, an UPDATE is a DELETE/INSERT anyway.

As ever, untested (yet) !

Cheers,
Norman.

Norman Dunbar.
Contract Oracle DBA.
Rivers House, Leeds.

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http://www.freelists.org/webpage/oracle-l Received on Thu Feb 16 2006 - 09:53:51 CST