RE: inefficient sql
- From: "Iotzov, Iordan" <IIotzov@xxxxxxxxxxxxxxx>
- To: "'Chris.Stephens@xxxxxxx'" <Chris.Stephens@xxxxxxx>, "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 30 May 2012 10:05:22 -0400
LIO to rows is indeed a good ratio to monitor. This ratio is, however,
practically meaningless for SQLs that do aggregates, such as COUNT, SUM, AVG,
etc. Separating aggregate from regular SQLs would be the biggest challenge for
an automated report.
Iordan Iotzov
http://iiotzov.wordpress.com/
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Stephens, Chris
Sent: Tuesday, May 29, 2012 4:15 PM
To: 'oracle-l@xxxxxxxxxxxxx'
Subject: inefficient sql
I'm interested in creating a daily report to run in our development
environments to spot inefficient SQL early in the process.
I've already got one that lists top ten highest elapsed time and top ten most
frequently executed. They have helped tremendously in focusing on the right
SQL. However, there is often SQL here that makes its way into integration and
production that could be improved upon. (Yes I know where SQL falls in the
optimization hierarchy and am well aware that business tasks are what are
important but these reports have proved their value over and over.)
I'm pretty confident that a ratio of LIO's to rows returned by each row
operation in an SQL execution plan is a good indicator of SQL efficiency. I
think I've heard this in a few different presentations. I don't, however,
recall what that ratio should be or if I'm misremembering completely.
What do you all consider good indicators of inefficient SQL and how to you
identify those statements?
Thanks!
Chris
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