John, Harrison,
----- Original Message ----- From: "John McCaskey" <[EMAIL PROTECTED]>
Newsgroups: mailing.database.myodbc
Sent: Friday, December 17, 2004 3:33 AM
Subject: Re: Relative efficiency (in terms of disk io) between REPLACE and
Ahhh, thats very good to know. Thank you.
On Wed, 2004-12-15 at 19:09 -0500, Harrison Fisk wrote:No.
In InnoDB an UPDATE is done as a DELETE/INSERT internally because it is multiversioning and it has to be able to rollback in case of a problem. So the UPDATE effectively does the same thing as the REPLACE that hits a problem. I would most likely stick with REPLACE since it is a bit easier to understand how it is working and has less client code.
I would like to correct that REPLACE in MySQL is semantically equivalent to a DELETE + INSERT, but internally MySQL often performs it as an UPDATE.
As Harrison noted, with REPLACE you can save in client/server communication, and therefore REPLACE is usually more efficient.
Note also that InnoDB buffers ibdata pages in its buffer pool. Calculating disk I/O for a certain workload is not easy.
Regards,
Harrison-- John A. McCaskey Software Development Engineer Klir Technologies, Inc. [EMAIL PROTECTED] 206.902.2027
Best regards,
Heikki Tuuri
Innobase Oy
Foreign keys, transactions, and row level locking for MySQL
InnoDB Hot Backup - a hot backup tool for InnoDB which also backs up MyISAM tables
http://www.innodb.com/order.php
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