Re: does update table with identical values actually write to disk?
- From: Riyaj Shamsudeen <riyaj.shamsudeen@xxxxxxxxx>
- To: clay.colburn@xxxxxxxxx
- Date: Thu, 4 Nov 2010 12:05:21 -0500
I blogged about this topic: An analysis based upon redo log file dumps.
http://orainternals.wordpress.com/2010/11/04/does-an-update-statement-modify-the-row-if-the-update-modifies-the-column-to-same-value/
Cheers
Riyaj Shamsudeen
Principal DBA,
Ora!nternals - http://www.orainternals.com - Specialists in Performance,
Recovery and EBS11i
Blog: http://orainternals.wordpress.com
OakTable member http://www.oaktable.com
Co-author: "Expert Oracle practices: Oracle Database Administration from the
Oak Table" http://www.apress.com/book/view/9781430226680
Co-author: "Pro Oracle SQL" http://www.apress.com/book/view/1430232285
On Mon, Nov 1, 2010 at 3:30 PM, Clay Colburn <clay.colburn@xxxxxxxxx> wrote:
> Sorry guys, I seemed to have committed at the wrong time. So it looks like
> the redo log is incremented when doing this operation. Thanks to Jared for
> pointing out the error!
>
>
> On Mon, Nov 1, 2010 at 12:57 PM, Rich Jesse <
> rjoralist2@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
>> Clay Colburn wrote:
>>
>> > For those not inclined to run through the example, the answer was that
>> it
>> > does not update the row, oracle intelligently skips the operation.
>>
>> Can you post your example? I've tried several tests where the data is
>> same/different, before/after commit, and multiple columns -- all unindexed
>> -- but am unable to find a correlation in the numbers resulting from
>> Jared's
>> query run before and after each test.
>>
>> It's probably something obvious that I'm not seeing. It *is* Monday after
>> all...
>>
>> Rich
>>
>> --
>> //www.freelists.org/webpage/oracle-l
>>
>>
>>
>
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