Re: RE: Delete + Insert versus Update
- From: MARK BRINSMEAD <mark.brinsmead@xxxxxxx>
- To: ineyman@xxxxxxxxxxxxxx
- Date: Thu, 16 Feb 2006 09:18:13 -0700
Another (maybe not so) subtle difference is that
DELETE/INSERT will hit *every* index, while updates
will touch only indexes on changed columns. (Won't
they? I really shouldn't be so daring with such
statements on a mailing list like this one!)
If a table is heavily indexed, this could make a
very substantial difference.
(Heaven help me, I have actually *seen* tables with
more indexes than columns!)
Anyway, I'm walking into the middle of this thread
without even seeing the original question. Apologies
if I'm off topic... (Or just plain hallucinating.)
Cheers,
-- Mark.
----- Original Message -----
From: oracle-l-bounce@xxxxxxxxxxxxx
Date: Thursday, February 16, 2006 9:02 am
Subject: RE: Delete + Insert versus Update
> Plus, if INSERT/DELETE executed from the app, it's an additional
> trip to
> the database through SQL*Net, when comparing to UPDATE.
>
> Igor
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Ric Van Dyke
> Sent: Thursday, February 16, 2006 10:54 AM
> To: norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx;
> peters@xxxxxxxxx
> Subject: RE: Delete + Insert versus Update
>
> 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
> -----------------------
> Hotsos Symposium, be there:
> http://www.hotsos.com/portal/events/SYM06
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Norman Dunbar
> Sent: Thursday, February 16, 2006 10:34 AM
> To: oracle-l@xxxxxxxxxxxxx; peters@xxxxxxxxx
> 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.
>
> Internal : 7 28 2051
> External : 0113 231 2051
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